Tektronix 453 schematic

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TM 11-6625-1722-15

TECHNICAL MANUAL

OPERATOR’S, ORGANIZATIONAL, DIRECT SUPPORT

GENERAL SUPPORT, AND DEPOT MAINTENANCE

MANUAL

OSCILLOSCOPE AN/USM-273

(NSN 6625-00-930-6637)

This copy is a reprint which includes current

pages from Changes 1.

HEADQUARTERS,

DEPARTMENT OF THE ARMY

JANUARY 1972

THIS MANUAL IS AN AUTHENTICATION OF THE MANUFACTURER’S COMMERCIAL LITERATURE WHICH, THROUGH USAGE, HAS BEEN FOUND TO COVER THE DATA REQUIRED TO OPERATE AND MAINTAIN THIS EQUIPMENT. SINCE THE MANIJAL WAS NOT PREPARED IN ACCORDANCE WITH MILITARY SPECIFICATION, THE FORMAT HAS NOT BEEN STRUCTURED TO CONSIDER LEVEL OF MAINTENANCE NOR TO INCLUDE A FORMAL SECTION ON DEPOT MAINTENANCE STANDARDS.

WARNING

DANGEROUS VOLTAGES

EXIST IN THIS EQUIPMENT

DON’T TAKE CHANCES!

CAUTION

Special 3% silver solder is required on the ceramic terminal

strips in this equipment. A 40- to 75-watt soldering iron should be used and it should be tinned with the same special

solder. Additional quantities of the solder may be procured under FSN 3439-912-8698. Ordinary solder may be used only in dire emergency.

This Manual Contains Copyrighted Material Reproduced

Permission Of

TM 11-6625-1722-15

ECHNICAL MANUAL

HEADQUARTERS

DEPARTMENT OF THE ARMY

NO. 11–6625–1722–15

ASHINGTON

, D.C., 10 January 1972

Operator’s Organizational, Direct Support, General Support, and Depot

Maintenance Manual Including Repair Parts and Special Tools Lists

OSCILLOSCOPE AN/USM–273

ECTION A.

INRODUCTION

CHARACTERISTICS

OPERATING INSTRUCTIONS . .. . . . . . . . . . . . . . . . . . . . .

CIRCUIT DESCRIPTION . . . . . . . . . . . . . . . . . .

MAINTENANCE

PERFOR0MANCE CHECK . . . . . . . . . . . . . . . . . . . . .

Page

A-1 1-1 2–1 3–1 4–1 5-1

10,

APPENDIX A.

C. D.

CALIBRATION

PREVENTIVE MAINTENANCE INSTRUCTIONS . . . . . . . . . . . . . . . . .

MECHNICAL PARTS IDENTIFICATION . . . . . . . . . . . . . . . . . . . . . . .

DIAGRAMS RACKMOUNTING REFERENCES

ITEMS COMPRISING AN OPERABLE EQUIPMENT . . . . . . . . . . . . . . . .

MAINTENANCE ALLOCATION . . . . . . . . . . . . . . .

REPAIR PARTS AND SPECIAL TOOLS LIST . . . . . . . . . . . . . .

6–1 7–1 8-1 9-1 10-1 A–1 B–1 C-1 D-1

TM 11-6625-1722-15

Fig. 1-1. Top; the Type 453 Oscilloscope. Bottom; the Type R453 Oscilloscope.

A-O

SECTION 0

INSTRUCTIONS

TM 11-6625-1722-15

0-1.

maintenance instructions.

Scope

This manual describes Oscilloscope

AN/USM-273 (fig. 1-1) and provides

Throughout this manual, the AN/USM-273 is re-

ferred to as the Tektronix Type 453 Oscilloscope. The maintenance allo-

cation chart appears in appendix C.

Repair parts and special tools lists

are contained in TM-6625-1722-24P.

0-2.

Indexes of Publications

a. DA Pam 310-4.

Refer to the latest issue of DA Pam 310-4 to deter-

mine whether there are new editions, changes, or additional publications pertaining to the equipment.

DA Pam 310-7.

Refer to DA Pam 310-7 to determine whether there

are modification work orders (MWO’S) pertaining to the equipment.

0-3.

Maintenance Forms, Records, and Reports

Reports of Maintenance and Unsatisfactory

Equipment.

Department

of the Army forms and procedures used for equipment maintenance will be those prescribed by TM 38-750, The Army Maintenance Management System.

Report of Packaging and Handling Deficiencies.

Fill out and for-

ward DD Form 6 (Packaging Improvement Report) as prescribed in AR 700-58/

NAVSUPINST 4030.29/AFR 71-13/MCO P4030.29A, and DLAR 4145.8.

Discrepancy

in Shipment Report (DISREP) (SF 361). Fill out and

forward Discrepancy in Shipment Report (DISREP) (SF 361) as prescribed in

AR 55-38/NAVSUPINST 4610.33B/AFR 75-18/MCO P4610.19C and DLAR 4500.15.

0-1

TM 11-6625-1722-15

0-4.

us an EIR.

don’t like about your equipment.

design.

(Quality Deficiency Report).

and Electronics Materiel Readiness Command, ATTN:

Monmouth, NJ 07703.

0-5.

Reporting Equipment Improvement Recommendations (EIR)

If your Oscilloscope AN/USM-273 needs improvement, let us know.

You,

the user,

are the only one who can tell us what you

Send

Let us know why you don’t like the

Tell us why a procedure is hard to perform.

Put it on an SF 368

Mail it to Commander, US Army Communications

DRSEL-ME-MQ, Fort

We’ll send you a reply.

Administrative Storage

Administrative storage of equipment issued to and used by Army activi-

ties shall be in accordance with TM 740-90–1.

0-6

Destruction of Army Electronics Materiel

Destruction of Army electronics materiel to prevent enemy use shall be

in accordance with TM 750-244-2.

0-7.

Reporting Errors and Recommending Improvements

You can help improve this manual. If you find any mistakes or if you

know of a way to improve the procedures, please let us know. Mail your

letter or DA Form 2028 (Recommended Changes to Publications and Blank

Forms) to

Readiness Command, ATTN:

either case,

Commander, US Army Communications and Electronics Materiel

DRSEL-ME-MQ, Fort Monmouth, NJ 07703. In

a reply will be furnished direct to you.

0-2

Change 1

SECTION 1

CHARACTERISTICS

TM 11-6625-1722-15

Introduction

The Tektronix Type 453 Oscilloscope is a transistorized portable oscilloscope designed to operate in a wide range of environmental conditions. The light weight of the Type 453 allows it to be easily transported, while providing the performance necessary for accurate high-frequency measurements. provides calibrated deflection factors from 5 millivolts to 10 volts/division. Channels 1 and 2 can be cascaded using an external cable to provide a one millivolt minimum defection factor (both VOLTS/DIV switches set to 5 mV).

The trigger circuits provide stable triggering over the full range of vertical frequency response. Separate trigger controls are provided to select the desired triggering for the A and B sweeps. One of three sweep modes can be selected for the A sweep; automatic, normal or single sweep. The horizontal sweep provides a maximum sweep rate of 0.1 microsecond/division (10 nanosecond/division using 10X magnifier) along with a delayed sweep feature for accurate relative-time measurements. can be made with Channel 2 providing the vertical deflection, and Channel 1 providing the horizontal [deflection. (TRIGGER switch set to CH 1 ONLY, HORIZ DISPLAY switch set to EXT HORIZ). The regulated DC power supplies maintain con-

The dual-channel DC-to-50 MHz vertical system

Accurate X-Y measurements

ELECTRICAL CHARACTERISTICS

VERTICAL DEFLECTlON SYSTEM

stant output over a wide variation of line voltages and frequencies. approximately 90 watts.

Information given in this instruction monual applies to the Type R453 also unless otherwise noted. The Type R453 is electrically identical to the Type 453 but is mechanically adapted for mounting in a standard 19-inch rack. Rackmounting instructions, a mechanical parts list and a dimensional drawing for the Type R453 are provided in Section

10 of this manual.

The electrical characteristics which follow are divided into two categories. Characteristics listed in the Performance Requirement column are checked in the Performance Check and Calibration sections of this manual. Items listed in the Operational Information column are provided for reference use and do not directly reflect the measurement capabilities of this instrument. The Performance Check procedure given in Section 5 of this manual provides a convenient method of checking the items listed in the Performance Requirement column. The following electrical characteristics

apply over a calibration interval of 1000 hours at an ambient temperature range of -15°C to +55°C, except as

otherwise indicated. Warm-up time for given accuracy is 20 minutes.

Total power consumption of the instrument is

. .

Characteristic

Deflection Factor

Deflection Accuracy

Variable Deflection Factor

Bandwidth at Upper -3 dB point (with or without P6010 Probe)

20 mV to 10 VOLTS/DIV 10 mV/DIV 5 mV/DIV

Channels land 2 cascaded

Risetime (calculated). With or

without P6010 Probe. 20 mV to 10 VOLTS/DIV

10 mV/DIV 5 mV/DIV Channels 1 and 2 cascaded

Performance Requirement

5 millivolts/division to 10 volts/division in 11 calibrated steps for each channel. One millivolt/ division when Channel 1 and 2 are cascaded.

Within ±3Y% of indicated deflection with VARlABLE control set to CAL. Cascaded deflection factor uncalibrated.

Uncalibrated deflection factor at least 2.5 times the VOLTS/DIV switch indication. This provides a maximum uncalibrated deflection factor of 25 volts/division in the 10 volts position.

DC to 50 MHz or greater

DC to 45 MHz or greater

DC to 40 MHz or greater

DC to 25 MHz or greater

Less than 7 nanoseconds Less than 7.8 nanoseconds Less than 8.75 nanoseconds Less than 14 nanoseconds

Operational Information

Steps in 1-2-5 sequence

With gain correct at 20 mV

Driven from 25-ohm source

Measured at one millivolt/division

Risetime calculated from bandwidth measurement using the formula:

Where:

= Risetime in nanoseconds.

BW = Bandwidth in megahertz.

1-1

TM 11-6625-1722-15

Characteristic

Input RC Characteristics

Maximum lnput Voltage

lnput Coupling Modes

AC Low-Frequency Response

(lower -3 dB point) Without probe

With P6010 Probe

Trace Shift Due to Input Gate

Current (at 25°C)

Vertical Display Modes

Chopped Repetition Rate

Attenuator Isolation Common Mode Rejection Ratio

Linear Dynamic Range Useful

for Common-Mode Relection in ADD Mode

Polarity Inversion Signal Delay Line

Low-Frequency

Vertical Linearity

Trace Drift (after 20 minute

warm up) 20 mV to 10 VOLTS/DIV

10 mV/DIV

5 mV/DIV

VERTICAL (cont)

Performance Requirement

AC or DC, selected by front-panel switch

Negligible

Channel 1 only Channel 2 only

Dual-troce, alternate between channels Dual-trace, chopped between channels Added algebraically

Approximately one-microsecond segments from each channel dispiayed at repetition rate of 500

kHz, ±20%. Greater than 10,000:1, DC to 20 MHz

Greater than 20:1 at 20 MHz for common-mode signals less than eight times VOLTS/DIV switch setting.

Signal on Channel 2 can be inverted

Less than 0.15 division compression or expansion

of two division signal when positioned to vertical

extremes of display area

Operational Information

Typically 1 megohm (±2%), paralleled

by 20 pF (±3%)

600 volts DC + peak AC (one kilohertz

or less). Peak-to-peak AC not to exceed 600 volts.

Typicaily 1.6 Hz, Input Coupling switch

set to AC Typically 0.16 Hz

With optimum GAIN frequency

Less than 10% incremental signal dis-

tortion for instantaneous input voltage

-10 or +10 times VOLTS/DIV

of switch setting

Approximately 140 nanoseconds

Includes CRT linearity. Measured with

one-kilohertz square wave.

Time

Typically less than Typically less than

0.03 division/hour

Typically less than

0.05 division/hour

Typically less than

0.08 division/hour

adjustment at low

Temperature

0.0075 division/degree C

Typically less than

0.0125 division/degree C

Typically less than

0.02 division/de-

gree C

Source

Coupling

Polarity

1-2

TRIGGERING (A AND B SWEEP)

Internal from displayed channel or from Channel

1 only Internal from AC power source External External divide by 10

AC low-frequency reject AC high-frequency reject

Sweep can be triggered from positive-going or

negative-going portion of trigger signal

TRIGGERING (cont)

TM 11-6625-1722-15

Characteristic

Internal Trigger Sensitivity

LF REJ

HF REJ

External Trigger Sensitivity

LF REJ

HF REJ

Auto Triggering (A sweep only)

Single Sweep (A sweep only)

Display Jitter

Maximum Input Voltage

External Trigger Input RC

Characteristics (approximate)

LEVEL Control Range

Performance Requirement

0.2 division of deflection, minimum, 30 Hz to 10 MHz; increasing to 1 division at 50 MHz

0.2 division of deflection, minimum, 30 Hz to 10

0.2 division of deflection, minimum, 30 kHz to 10

0.2 division of deflection, minimum, 30 Hz to 50 kHz

0.2 division of deflection, minimum, DC to 10 MHz; increasing to 1 division at 50 MHz

50 millivolts, minimum, 30 Hz to 10 MHz; increasing to 200 millivolts at 50 MHz

50 millivolts, minimum, 30 kHz to 10 MHz; increasing to 200 millivolts at 50 MHz

50 millivolts, minimum, 30 Hz to 50 kHz

50 millivolts, minimum, DC to 10 MHz; increas-

ing to 200 millivolts at 50 MHz Stable display presented with signal amplitudes

given under Internal and External Trigger Sensitivity above 20 Hz. Presents a free-running sweep for lower frequencies or in absence of trigger signal.

A Sweep Generator produces only one sweep

when triggered. Further sweeps are locked out

until RESET button is pressed. Trigger sensitivity same as given above.

Less than 1 nanosecond at 10 nanoseconds/division sweep rate (MAG switch set to X10)

At least ±2 volts, SOURCE switch in EXT position. At least ±20 volts, SOURCE switch in EXT

÷10 position

Operational Information

Typical -3 dB point, 16 Hz

Typical -3 dB point, 16 kHz

Typical -3 dB points, 16 Hz and 100 kHz

Typical -3 dB point, 16 Hz

Typical -3 dB point, 16 kHz

Typical -3 dB points, 16 Hz and 100

kHz

600 volts DC + peak AC (one kilohertz

or less). Peak-to-peak AC not to exceed

600 volts. 1 Megohm paralleled by 20 pF, except

in LF REJ

Sweep Rates

A Sweep

B sweep

Sweep Accuracy-A and B

Sweep 5 s to 0.1 s/DIV

50 ms to 0.1 µs/DIV

Variable Sweep Rate

HORIZONTAL DEFLECTION SYSTEM

A and B Sweep Generator

0.1 microsecond/division to 5 seconds/division in

24 calibrated stem

0.1 microsecond/division to 0.5 second/division

in 21 calibrated steps

0°C to +40°C

Within ±3% of indi- Within ±5% of indi-

cated sweep rate

Within ±3% of indi- Within ±4% of indi-

cated sweep rate

Uncalibrated sweep rate to at least 2.5 times the

TIME/DIV indication, or a maximum of at least

12.5 seconds/division in the 5 s position (B sweep,

maximum of 1.25 seconds/division in the .5 s

position.

-15°C to +55°C

cated sweep rate

A sweep is main and delaying sweep

B sweep is delayed sweep

A VARIABLE and B TIME/DiV VARlABLE controls set to CAL

1-3

TM 11-6625-1722-15

A and B Sweep Generotor

Characteristic

Sweep Length

A sweep

B sweep

Sweep Hold-off-A sweep

5s to 10

Sweep Magnification

Magnified Sweep Accuracy 1% tolerance added to speclfled sweep accuracy Magnified Sweep Linearity

Normal/Magnified Registration

Calibrated Delay Time Range

DELAY-TIME MULTIPLIER

Dial Range

Delay Time Accuracy

5s to 0.1 s/DIV

50 ms to 1

Incremental Multiplier Linearity Delay Time Jitter

Variable from less than 4 divisions to 11.0, ±0.5 division

11.0 divisions, ±0.5 division

Less than one times the A TIME/DIV switch set-

ting

Less than 2.5 microseconds

Each sweep rate can be increased 10 times the Extends fastest sweep rate to 10 nano-

indicated sweep rate by horizontally expanding seconds/division the center division of display

±1.5% for any eight division portion of the total magnified sweep length (excluding first

and last 60 nanoseconds of magnified sweep)

±0.2 division, or less, trace shift at graticuie center when switching MAG switch from X10 to OFF

Continuous from 50 seconds to 1 microsecond A VARIABLE control set to CAL for indi-

0.20 to 10.20 0°C to +40°C -15° C to +55° C Within ±2.5% of indi-

cated delay cated delay Includes incremental multiplier linearity Within ±1.5% of indi-

cated delay cated delay

±0.2% Less than 1 part in 20,000 of 10 times A TIME/

DIV switch setting

Performance Requirement

Sweep Magnifier

Sweep Delay

Within ±3.5% of indi-

‘Within ±2% of indi-

±0.3%.

Operational Information

A TIME/DIV switch set to 1 ms

B TIME/DIV switch set to 1 ms

cated delay

Equal to 0.5 division, or less, with the A TIME/DIV switch set to 1 ms and the B TIME/DIV switch set to 1

Input to Channel 1 (TRIGGER

switch in CH 1 ONLY) Deflection factor

Accuracy

X Bandwidth at Upper -3 dB

Point

Input RC characteristics

Phase difference between X

and Y amplifiers at 50 kHz

Input to EXT HORIZ Connector

Deflection factor

1-4

External Horizontal Amplifier

5 millivolts/division to 10 volts/division in 11 calibrated steps

0°C to +40°C Within ±5% of indi- Within ±8% of indi-

cated deflection

5 MHz or greater

Less than 3°

B SOURCE switch in EXT; 270 millivolts/division, ±15%. B SOURCE switch in EXT

±20%

cated deflection

Steps in 1-2-5 sequence.

Channel 1 VARIABLE control does not affect horizontal deflection

With external horizontal gain correct

at 20 mV

Typically 1 megohm (±2%), paralleled

by 20 pF (±3%)

External Horizontal Amplifier (cont)

X Bandwidth at Upper -3 5 MHz or greater

TM 11-6625-1722-15

Operational Information

—

Input RC characteristics

(approximate]

Phase difference between X

and Y amplifiers at 50kHz

CALIBRATOR

Waveshape Polarity Output Voltage

Output Current

Square wave Positive going with baseline at zero volts

0.1 volt or 1 volt, peak to peak

5-milliamperes through PROBE LOOP on side

Repetition Rate

Voltage Accuracy

.Current Accuracy Repetition Rate Accuracy Risetime Duty CycIe

±0.5%

Less than 1 microsecond

49% to 51%

Output Resistance

Z AXIS INPUT

Sensitivity

5 volt peak-to-peak signal produces noticeable

modulation Usable Frequency Range DC to greater than 50 MHz Input Resistance at DC Input Coupling DC coupled Polarity of Operation

1 megohm, paralleled by 20 pF

Less than 3°

Selected by CALIBRATOR switch on side

panel

±1.5%

Approximately 200 ohms in 1 V position. Approximately 20 ohms in .1 V position.

Approximately 47 kilohms

Positive-going input signal decreases trace intensity Negative-going signal increases trace

Maximum Input Voltage

A and B Gate

Waveshape Amplitude Polarity Duration

Output resistance

Vertical Signal Out (CH 1 only)

Output voltage

Bandwidth

Output coupling

Output resistance

OUTPUT SIGNALS

—

Rectangular pulse

Posltlve-going with baseline at about -0.7 volts.

I Same duration as the respective sweep

25 millivolts, or greater/division of CRT display into 1 megohm load.

DC to 25 MHz or greater when cascaded with

Channel 2 or into 50-ohm load.

DC coupled

200 volts combined DC and peak AC

A GATE duration variable between about 4 and 11 times the A TIME/DIV switch setting

with the A SWEEP

LENGTH control. Approximately 1.5 kilohms

Approximately 50 ohms

1-5

TM 11-6625-1722-15

Characteristic

Line Voltage Voltage Ranges (AC, RMS)

115-volts nominal

230-volts nominal

Line Frequency

Maximum Power Consumption

at 115 Volts, 60 Hz

Tube Type Phosphor

Accelerating Potential

Graticule

Type

Area

Illumination

Unblinking

Raster Distortion

Trace Finder

POWER SUPPLY

Performance Requirement

115 volts nominal or 230 volts nominal

90 to 110 volts 104 to 126 volts 112 to 136 volts

180 to 220 volts 208 to 252 volts 224 to 272 volts

——— 48 to 440 Hz

CATHODE-RAY TUBE (CRT)

Internal Six divisions vertical by 10 divisions horizontal.

Each division equals 0.8 centimeter.

0.1 division or less total

Limits display within graticule area when pressed.

Operational Information

.—

Line voltage and range selected by Line Voltage Selector assembly on rear panel. Voltage ranges apply for waveform distortion which does not reduce the peak line voltage more than 5% below the true sine-wave peak value.

92 watts (105 volt-amperes)

Tektronix T4530-31-1 rectangular

P31 standard. Others available on

special order. Approximately 10 kV total (cathode

potential -1.95 kV).

Variable edge lighting Bias-type, DC coupled to CRT grid. Adjustable with Geometry and Y Axis

Align adjustments.

Characteristic

Temperature

Operating

Non-operating

Altitude

Operating

Non-operating

Humidity

Non-operating

Vibration

Operating and non-operating

Shock

Operating and non-operating

ENVIRONMENTAL CHARACTERISTICS

The following environmental test limits apply when tested in accordance with the recommended test procedure. This instrument will meet the electrical characteristics given in this section following environmental test. including failure criteria, etc., may be obtained from Tektronix, Inc. Contact your local Tektronix Field Office or representative.

Performance Requirement

-15°C to +55°c

-55° to +75°C

15,000 feet maximum

50,000 feet maximum

Five cycles (120 hours) of Mil-Std-202C, Method 106B

15 minutes along each of the three major axes at a total displacement of 0.025-inch peak to peak (4 g at 55 c/s) with frequency varied from 10-5510 c/s in one-minute cycles. Hold at 55 c/s for three minutes on each axis.

Two shocks of 30 g, one-half sine, 11 millisecond

duration each direction along each major axis.

Complete details on environmental test procedures,

Supplemental Information

Fan at rear circulates air throughout instrument. cutout protects instrument from overheating.

Derate maximum operating tempera-

ture by 1°C/1000 feet change in altitude above 5000 feet.

Exclude freezing and vibration

Instrument secured to vibration platform during test. Total vibration time, about 55 minutes.

Guillotine-type shocks. Total of 12 shocks

Automatic resetting thermal

1-6

ENVIRONMENTAL CHARACTERISTICS (cont)

TM 11-6625-1722-15

Characteristic

Transportation

Package vibration

Package drop

Type 453 Type R453

MECHANICAL CHARACTERISTICS

Characteristic

Construction

Chassis

Panel

Cabinet Circuit boards

Overall Dimensions, Type

453 (measured ot maximum points) Height

Width

Length

Overall Dimensions, Type

R453 (measured at maximum points)

Height

Performance Requirement

Meets National Safe Transit type of test when

packaged as shipped from Tektronix, Inc. One hour vibration slightly in excess of 1 g.

30-inch drop on any corner, edge or flat surface.

18-inch drop on any corner, edge or flat surface.

Width

Information

Length

Aluminum alloy Aluminum alloy with ano-

dized finish Blue vinyl-coated aluminum Glass-epoxy laminate

Connectors

Z AXIS INPUT All other connectors

Net Weight

Type 453 (includes front

cover without accessor-

Type R453 (without ac-

handle positioned for carrying.

Standard accessories supplied with the Type 453 and R453 are listed on the last pullout page of the Mechanical Parts List illustrations.

7 inches

Operational Information

Package should just leave vibration surface

19 inches

panel;

Binding post BNC

Approximately 29 pounds.

ies)

Approximately 32 pounds.

cessories)

STANDARD ACCESSORIES

1-7

SECTION 2

OPERATING INSTRUCTIONS

General

O effectively use the Type 453, the operation and capa-

T bilities of the instrument must be known. This section describes the operation of the front-, side- and rear-panel controls and connectors, gives first time and general operating information and lists some basic applications for this instrument.

Front Cover and Handle

The front cover furnished with the Type 453 provides a dust-tight seal around the front panel. Use the cover to protect the front panel when storing or transporting the instrument. The cover also provides storage space for probes and other accessories (see Fig. 2-1).

TM 11-6625-1722-15

Fig. 2-1. Accessory storage provided in front cover.

The handle af the Type 453 can be positioned for carrying

or as a tilt-stand for the instrument. To position the handle,

press in at both pivot points (see Fig. 2-2) and turn the handle to the desired position. Several positions are provided for convenient carrying or viewing. The instrument

may also be set an the rear-panel feet for operation or storage.

Operating Voltage

The Type 453 can be operated from either a 115-volt or

a 230-volt nominal line-voltage source. The Line Voltage

Fig. 2-2. Handle positioned to provide a stand for the instrument

Selector assembly on the rear panel converts the instrument from one operating range to the other. In addition, this assembly changes the primary connections of the power transformer to allow selection of one of three regulating ranges. The assembly also includes the two line fuses. When the instrument is converted from 115-volt to 230-volt nominal operation, or vice versa, the assembly connects or disconnects one of the fuses to provide the correct protection for the instrument. Use the following procedure to convert this instrument between nominal line voltages or regulating ranges.

1. Disconnect the instrument from the power source.

2. Loosen the two captive screws which hold the cover onto the voltage selector assembly; then pull to remove the cover.

3. To convert from 115-volts nominal to 230-volts nominal line voltage, pull out the Voltage Selector switch bar (see Fig. 2-3]; turn it around 180° and plug it back into the remaining holes. Change the line-cord power plug to match the power-source receptacle or use a 115- to 230-volt adapter.

4. To change regulating ranges, pull out the Range Selector switch bar (see Fig. 2-3); slide it to the desired position and plug it back in. Select a range which is centered about the average line voltage to which the instrument is to be connected (see Table 2-1).

5. Re-install the cover and tighten the two captive screws.

6. Before applying power to the instrument, check that the indicating tabs on the switch bars are protruding through the correct holes for the desired nominal line voltage and

regulating range.

2-1

TM 11-6625-1722-15

Fig. 2-3. Line Voltage Selector assembly on the rear panel (shown with cover removed).

CAUTION

The Type 453 should not be operated with the Voltage Selector or Range Selector switches in the

wrong positions for the line voltage applied. Operation of the instrument with the switches in the wrong positions may either provide incorrect aperotion or damage the instrument.

TABLE 2-1

more frequently. The air filter should be cleaned occasion-

ally to aII

OW the maximum amount of cooling air to enter

the instrument. Cleaning instructions are given in Section 4.

The Type 453 can be operated where the ambient air

temperature is between

-15°C and +55°C. Derate the maximum operating temperature 1°C for each additional 1000 feet of altitude above 5000 feet. This instrument can be stored in ambient temperatures between –55°C and

+75°C. After storage at temperatures beyond the operating limits, allow the chassis temperature to come within the operating limits before power is applied.

Rackmounting

Complete information for mounting the Type R453 in a

cabinet rack is given in Section 10 of this manual.

CONTROLS AND CONNECTORS

A brief description of the function or operation front-, side- and rear-panel controls and connectors (see Fig. 2-4). More detailed information is given

of the follows in this

section under General Operating Information.

Cathode-Ray Tube

INTENSITY FOCUS

Controls brightness of display. Provides adjustment for a well-defined dis-

play. SCALE ILLUM TRACE FINDER

Controls graticule illumination.

Compresses display within graticule area

independent of display position or appli-

ed signals.

Operating Temperature

The Type 453 is cooled by air drawn in at the rear and

blown out through holes in the top and bottom covers. Adequate clearance on the top, bottom and rear must be provided to allow heat to be dissipated away from the instru-

ment. The clearance provided by the feet at the bottom and

rear should be maintained. If possible, allow about one inch of clearance on the top. Do not block or restrict the air flow from the air-escape holes in the cabinet.

A thermal cutout in this instrument provides thermal protection and disconnects the power to the instrument if the internal temperature exceeds a safe operating level. Operation of the instrument for extended periods without the covers may cause it to overheat and the thermal cutout to open

Vertical (both

VOLTS/DIV

VARIABLE

UNCAL

POSITION GAIN

Input Coupling (AC GND DC)

channels except as noted)

Selects vertical deflection factor (VARlABLE control must be in CAL position for indicated deflection factor).

Provides continuously variable deflection factor between the calibrated settings of

the VOLTS/DIV switch. Light indicates that the VARIABLE control

is not in the CAL position. Controls vertical position of trace. Screwdriver adjustment to set gain of the

Vertical Preamp. Line between adjustment and 20 mV VOLTS/DIV position indicates that gain should be set with VOLTS/DIV switch in this position.

Selects method of coupling input signal to Vertical Deflection System.

AC: DC component of input signal is

blocked. Low frequency limit -3 dB point) is about 1.6 hertz.

GND: Input circuit is grounded (does not

ground applied signal).

2-2

TM 11-6625-1722-15

Fig. 2-4. Front-, side- and rear-panel controls and connectors.

2-3

TM 11-6625-1722-15

DC: All components of the input signal are

passed to the Vertical Deflection System.

STEP ATTEN

BAL

INPUT

MODE

TRIGGER

INVERT (CH 2

only)

A and B Triggering (both where applicable)

EXT TRIG

INPUT

SOURCE

Screwdriver adjustment to balance Vertical Deflection System in the 5, 10 and 20 mV positions of the VOLTS/DIV switch.

Vertical input connector for signal. Selects vertical mode of operation.

CH 1: The Channel 1 signal is displayed. CH 2: The Channel 2 signal is displayed. ALT: Dual trace display of signal on both

channels. Display switched at end of each sweep.

CHOP: Dual trace display of signal on

both channels. Approximately one-microsecond segmerlts from each channel displayed at a repetition rate of about 500 kilohertz.

ADD: Channel 1 and 2 signals are alge-

braically added and the algebraic sum is displayed on the CRT.

Selects saurce of internal trigger signal from vertical system.

NORM: Sweep circuits triggered from dis-

played channel(s). Channel 1 signal

available at CH 1 OUT connector.

CH 1 ONLY: Sweep circuits triggered only

from signal applied to the Channel 1

INPUT connector. No signal available at CH 1 OUT connector. CH 1 lights, located beside A and B SOURCE switches indicate when the TRIGGER switch is in the CH 1 ONLY position.

Inverts the Channel 2 signal when pulled

out.

Input connector for external trigger signal. Connector in B Triggering section of front panel also serves as external horizontal input when HORIZ DISPLAY switch is in EXT HORIZ position and B SOURCE switch is in EXT position.

Selects source of trigger signal. INT: Internal trigger signal obtained from

Vertical Deflection System. When CH

1 light is on, trigger signal is obtained

only from the Channel 1 input signal; when the light is off, the trigger signal

is abtained from the displayed chan-

nel(s). Source of internal trigger signal

is selected by the TRIGGER switch.

LINE: Trigger signal obtained from a sam-

ple of the line voltage applied to this

instrument.

EXT: Trigger signal obtained from an ex-

ternal signal applied to the EXT TRIG INPUT connector.

nal approximately 10 times.

CH 1

COUPLING

SLOPE

LEVEL

HF STAB Decreases display jitter for high-frequency

(A Triggering only) sweep rates.

A and B Sweep

DELAY-TIME

MULTIPLIER

A SWEEP

TRIG’D

UNCAL A

OR B

A AND B

TIME/DIV AND DELAY TIME

Light indicates that the internal trigger signal is abtained only from the signal connected to the Channel 1 INPUT connector (see TRIGGER switch).

Determines method of coupling trigger signal to trigger circuit.

AC: Rejects DC and attenuates signals be-

low about 30 hertz. Accepts signals between abaut 30 hertz and 50 megahertz.

LF REJ: Rejects DC and attenuates signals

below about 30 kilohertz. Accepts signals between about 30 kilohertz and 50 megahertz.

HF REJ: Accepts signals between about 30

hertz and 50 kilohertz; rejects DC and attenuates signals outside the above range.

DC: Accepts all trigger signals from DC to

50 megahertz or greater.

Selects portion of trigger signal which

starts the sweep.

+: Sweep can be triggered from positive-

going portion of trigger signal.

-: Sweep can be triggered from negativegoing portion of trigger signal.

Selects amplitude point on trigger signal

at which sweep is triggered.

signals. Has negligible effect at lower

Provides variable sweep delay between

0.20 and 10.20 times the delay time indi-

cated by the A TIME/DIV switch.

Light indicates that A sweep is triggered and will produce a stable display with correct INTENSITY and POSITION control settings.

Light indicates that either the A or B

VARIABLE control is not in the CAL posi-

tion.

A TIME/DIV switch (clear plastic flange)

selects the sweep rate of the A sweep

circuit for A sweep only operatian and selects the basic delay time (to be multi-

plied by DELAY-TIME MULTIPLIER dial setting) for delayed sweep operation.

B TIME/DIV (DELAYED SWEEP) switch selects sweep rate of the B sweep circuit

Attenuates external trigger sig-

2-4

TM 11-6625-1722-15

A VARIABLE

B SWEEP

MODE

HORIZ

DISPLAY

MAG

A SWEEP

MODE

for delayed sweep operation only. VARlABLE controls must be in CAL positions for calibrated sweep rates.

Provides continuously variable A sweep rate to at least 2.5 times setting of the A TIME/DIV switch. A sweep rate is calibrated when control is set fully clockwise to CAL.

Selects B sweep operation mode. TRIGGERABLE AFTER DELAY TIME: B

sweep circuit will not produce a sweep until a trigger pulse is received following the delay time selected by the DELAY TIME (A TIME/DIV) switch and

the DELAY-TIME MULTIPLIER dial.

B STARTS AFTER DELAY TIME: B sweep

circuit runs immediately following delay time selected by the DELAY TIME switch

and DELAY-TIME MULTIPLIER dial. Selects horizontal mode of operation. A: Horizontal deflection provided by A

sweep.

B sweep inoperative.

A INTEN DURING B: Sweep rate deter-

mined by A TIME/DIV switch. An inten-

sified portion appears on the sweep

during the B sweep time. This position

provides a check of the duration and position of the delayed sweep (B) with respect to the delaying sweep (A).

DELAYED SWEEP (B): Sweep rate deter-

mined by B TIME/DIV switch with the delay time determined by the setting of the DELAY TIME (A TIME/DIV) switch and the DELAY-TIME MULTIPLIER dial. Sweep mode determined by B SWEEP

MODE switch.

EXT HORIZ: Horizontal deflection pro-

vided by an external signal.

Increases sweep rate to ten times setting of A or B TIME/DIV switch by horizontally expanding the center division of the display. Light indicates when magnifier is

on.

Determines the operating mode for A sweep.

AUTO TRIG: Sweep initiated by the ap-

plied trigger signal using the A Trig-

gering controls when the trigger signal repetition rate is above about 20 hertz. For lower repetition rates or when there is no trigger signal, the sweep free runs at the sweep rate selected by the A TIME/DIV switch to produce a bright reference trace.

NORM TRIG: Sweep initiated by the ap-

plied trigger signal using the A Trig-

gering controls. No trace is displayed when there is no trigger signal.

RESET

A SWEEP

LENGTH

POSITION FINE

1 kHz CAL POWER ON

Side Panel ASTIG

B TiME/DIVVARIABLE

PROBE LOOP

A GATE

B GATE

CH 1 OUT

SINGLE SWEEP: After a sweep is display-

ed, further sweeps cannot be presented until the RESET button is pressed. Display is triggered as for NORM operation using the A Triggering controls.

When the RESET button is pressed (SINGLE SWEEP mode), a single display will be presented (with correct triggering) when the next trigger pulse is received. RESET light (inside RESET button) remains on until a trigger is received and the sweep is completed. RESET button must be pressed before another sweep can be presented.

Adiusts length of A sweep. In the FULL

position (clockwise detent), the sweep is about 11 divisions long. As the control is rotated counterclockwise, the length of A sweep is reduced until it is less than four divisions long iust before the detent in the fully-counterclockwise position is reached. In the B ENDS A position (counterclockwise detent), the A sweep is reset at the end of the B sweep to provide the fastest possible sweep repetition rate for delayed sweep displays.

Controls horizontal position of trace. Provides more precise horizontal position

adjustment. Calibrator output connector. Light: Indicates that POWER switch is

on and the instrument is connected to a line voltage source.

Switch: Controls power to the instrument.

Screwdriver adjustment used in conjunction with the FOCUS control to obtain a well-defined display. Does not require readjustment in normal use.

Provides continuously variable sweep rate to at least 2.5 times setting of B TIME/DIV switch. B sweep rate is calibrated when control is set fully clockwise to CAL.

Current loop providing five-milliampere square-wave current from calibrator circuit.

Output connector providing a rectangular

pulse coincident with A sweep. Output connector providing a rectangular

pulse coincident with B sweep. Output connector providing a sample of

the signal applied to the Channel 1 lN-

PUT connector when the TRIGGER switch

is in the NORM position.

2-5

TM 11-6625-1722-15

CALIBRATOR

TRACE

ROTATION

Rear Panel

Z AXIS INPUT

Line Voltage

Selector

The following steps will demonstrate the use of the controls and connectors of the Type 453. It is recommended that this procedure be followed completely for familiarization with this instrument.

Setup Information

1. Set the front-panel controls as follows:

CRT Controls

INTENSITY FOCUS SCALE ILLUM Counterclockwise

Vertical Controls (both channels if applicable)

VOLTS/DIV 20 mV VARIABLE POSITION Midrange

INPUT COUPLING MODE TRIGGER

INVERT

Triggering Controls (both A and B if applicable)

LEVEL SLOPE COUPLING SOURCE

Sweep Controls

DELAY-TIME

MULTIPLIER A and B TIME/DIV A VARIABLE B SWEEP MODE

Switch selects output voltoge of Calibrator.

1-volt or 0.1-volt square wave available.

Screwdriver adjustment to align trace with horizontal graticule lines.

Input connector for intensity modulation of the CRT display.

Switching assembly to select the nominal operating voltage and the line voltage range. line fuses.

Voltage Selector: Selects nominal operat-

Range Selector: Selects line voltage range

FIRST-TIME OPERATION

The assembly also includes the

ing voltage range (115V or 230V).

(low, medium, high).

Counterclockwise Midrange

CAL

DC CH 1 NORM Pushed in

Clockwise (+)

INT

0.20

.5 ms

CAL

B STARTS AFTER

DELAY TIME

HORIZ DISPLAY MAG POSITION A SWEEP LENGTH A SWEEP MODE POWER

Side-Panel Controls

B TIME/DIV VARIABLE CALIBRATOR

2. Connect the Type 453 to a power source that meets the voltage and frequency requirements of the instrument. If the available line voltage is outside the limits of the Line Voltage Selector assembly position (on rear panel), see Operating Voltage in this section.

3. Set the POWER switch to ON. Allow about five minutes warmup so the instrument reaches a normal operating temperature before proceeding.

CRT Controls

4. Advance the INTENSITY control until the trace is at the desired viewing level (near midrange).

5. Connect the 1 kHz CAL connector to the Channel 1

INPUT connector with a BNC cable.

6. Turn the A LEVEL control toward 0 until the display

becomes stable. Note that the A SWEEP TRIG’D light is on

when the display is stable.

7. Adiust the FOCUS control for a sharp, well-defined display over the entire trace length. (If focused display can-

not be obtained, see Astigmatism Adjustment in this section.)

8. Disconnect the input signal and move the trace with the Channel 1 POSITION control so it coincides with one of the horizontal graticule lines. the graticule line, see Trace Alignment Adjustment in this

section.

9. Rotate the SCALE ILLUM control throughout its range and notice that the graticule lines are illuminated as the

control is turned clockwise (most obvious with mesh or smokegray filter installed). Set control so graticule lines are illuminated as desired.

Vertical Controls

10. Change the CH 1 VOLTS/DIV switch from 20 mV to 5 mV. If the vertical position of the trace shifts, see Step Attenuator Balance in this section.

11. Set the CH 1 VOLTS/DIV switch to 20 mV and set the Channel 1 Input Coupling switch to AC. Connect the 1 kHz CAL connector to both the Channel 1 and 2 INPUT connectors with two BNC cables and a BNC T connector.

If the BNC cables and BNC T connector are not

available, make the following changes in the procedure. Place the BNC jack post (supplied accessory) on the 1 kHz CAL connector and connect

A OFF Midrange FULL AUTO TRIG OFF

CAL .1 V

If the trace is not parallel with

NOTE

2-6

TM 11-6625-1722-15

the Channel 1 and 2 INPUT connectors. Connect the probe tips to the BNC jack post. Set the CALIBRATOR switch (on side-panel) to 1 V.

12. Turn the Channel 1 POSITION control to center the display. The display is a square wave, five divisions in amplitude with about five cycles displayed on the screen. If the display is not five divisions in amplitude, see Vertical

Gain Adjustment in this section.

13. Set the Channel 1 Input Coupling switch to GND ond

position the trace to the center horizontal line.

14. Set the Channel 1 Input Coupling switch to DC. Note that the baseline of the waveform remains at the center horizontal line (ground reference).

15. Set the Channel 1 Input Coupling switch to AC. Note that the waveform is centered about the center horizontal line.

16. Turn the Channel 1 VARIABLE control throughout its range. Note that the UNCAL light comes on when the VARl-

ABLE control is moved from the CAL position (fully clockwise). The deflection should be reduced to about two divisions. Return the VARIABLE control to CAL.

17. Set the MODE switch to CH 2.

18. Turn the Channel 2 POSITION control to center the

display. The display will be similar to the previous display for Channel 1. Check Channel 2 step attenuator balance and gain as described in steps 10 through 12. The Channel 2

input Coupling switch and VARIABLE control operate as

described in steps 13 through 16.

19. Set both VOLTS/DIV switches to 50 mV.

20. Set the MODE switch to ALT and position the Channel

1 waveform to the top of the graticule area and the Chan-

nel 2 waveform to the bottom of the graticule area. Turn

the A TIME/DIV switch throughout its range. Note that the display alternates between channels at all sweep rates.

Triggering

25. Set the CALIBRATOR switch to 1 V. Rotate the A LEVEL control throughout its range. The display free runs at the extremes of rotation. Note that the A SWEEP TRIG'D light is on only when the display is triggered.

26. Set the A SWEEP MODE switch to NORM TRIG. Again rotate the A LEVEL control throughout its range. A display is presented only when correctly triggered. The A SWEEP TRIG'D light operates as in AUTO TRIG. Return the A SWEEP MODE switch to AUTO TRIG.

27. Set the A SLOPE switch to -. The trace starts on the negative part of the square wave. Return the switch to +; the trace starts with the positive part of the square wave.

28. Set the A COUPLING switch to DC. Turn the Channel 1 POSITION control until the display becomes unstable (only part of square wave visible). Return the A COUPLING

switch to AC; the display is again stable. Since changing

trace position changes DC level, this shows how DC level

changes affect DC trigger coupling. Return the display to

the center of the screen.

29. Set the MODE switch to CH 2; the display should be

stable. Remove the signal connected to Channel 1; the dis-

play free runs.

Set the TRIGGER switch to NORM; the dis-

play is again stable. Note that the CH 1 lights in A and B

Triggering go out when the TRIGGER switch is changed to

NORM.

30. Connect the Calibrator signal to both the Channel 2

INPUT and A EXT TRIG INPUT connectors. Set the A

SOURCE switch to EXT. Operation of the LEVEL, SLOPE and COUPLING controls for external triggering are the same as described in steps 25 through 28.

31. Set the A SOURCE switch to EXT is the same as for EXT. Note that the A LEVEL control has less range in this position, indicating trigger signal attenuation. Return the A SOURCE switch to INT.

32. Operation of the B Triggering controls is similar to A Triggering.

21. Set the MODE switch to CHOP and the A TIME/DIV Note the switching between channels as

shown by the segmented trace. Set the TRIGGER switch to

CH 1 ONLY; the trace should appear more solid, since it is no longer triggered on the between-channel switching trans-

ients. Turn the A TIME/DIV switch throughout its range. A dual-trace display is presented at all sweep rates, but unlike ALT, both channels are displayed on each trace on a timesharing basis. Return the A TIME/DIV switch to .5 ms.

22. Set the MODE switch to ADD. The display should be four divisions in amplitude. Note that either POSITION control moves the display.

23. Pull the INVERT switch. The display is a straight line indicating that the algebraic sum of the two signals is zero (if the Channel 1 and 2 gain is correct).

24. Set either VOLTS/DIV switch to 20 mV. The square-

wave display indicates that the algebraic sum of the two

signals is no longer zero.

Return the MODE switch to CH 1

and both VOLTS/DIV switches to .2 (if using 10X probes,

set both VOLTS/DIV switches to 20 mV). Push in the INVERT switch.

Normal and Magnified Sweep

33. Set the A TIME/DIV switch to 5 ms and the MAG switch to X10. The display should be similar to that obtained with the A TIME/DIV switch set to .5 ms and the MAG switch to OFF.

34. Turn the horizontal POSITION control throughout its range; it should be possible to position the display across the complete graticule area. Now turn the FINE control. The

display moves a smaller amount and allows more precise positioning. Return the A TIME/DIV switch to .5 ms, the

MAG switch to OFF and return the start of the trace to the left graticule line.

Delayed Sweep

36. Pull the DELAYED SWEEP knob out and turn it to 50

(DELAY TIME remains at .5 ms). Set the HORIZ DISPLAY switch to A INTEN DURING B. An intensified portion, about one division in length, should be shown at the start of the trace. Rotate the DELAY-TIME MULTIPLIER dial throughout its range; the intensified portion should move along the display.

2-7

TM 11-6625-1722-15

37. Set the B SWEEP MODE switch to TRIGGERABLE

AFTER DELAY TIME. Again rolate the DELAY-TIME MULTI-

PLIER dial throughout its range and note that the intensified portion appears to jump between posltive slopes of the display. Set the B SLOPE switch to -; begins on the negative slope.

the intensified portion

Rotate the B LEVEL control; the intensified portion of the display disappears when the B LEVEL control is out of the trlggerable range. Return the B LEVEL control to 0.

38. Set the HORIZ DISPLAY switch to DELAYED SWEEP (B). Rotate the DELAY-TIME MULTIPLIER dial througout its range; about one-half cycle of the waveform should be

displayed on the screen (Ieading edge visible only at high

INTENSITY control setting). The display remains stable on the screen, indicating that the B sweep is triggered.

39. Set the B SWEEP MODE switch to B STARTS AFTER

DELAY TIME. Rotate the DELAY-TIME MULTIPLIER dial

throughout its range; the display moves continously across the screen as the control is rotated.

40. Rotate the DELAYTIME MIULTIPLIER dial fully counter-

clockwise and set the HORIZ DISPLAY switch to A INTEN

DURING B. Rotate the A SWEEP LENGTH control counter-

clockwise; the Iength of the display decreases. Set the con-

trol to the B ENDS A position; now the display ends after the intensified portion. Rotate the DELAY-TIME MULTIPLIER dial ond note that the sweep length increases as the display moves across the screen. Return the A SWEEP LENGTH con-

trol to FULL and the HORIZ DISPLAY switch to A.

Single Sweep

41. Set the A SWEEP MODE switch to SINGLE SWEEP. Remove the Calibrator signal from the Channel 2 INPUT connector. Press the RESET button; the RESET light should come on and remain on. Again apply the signal to the Channel 2 INPUT connector; a single trace should be presented

and the RESET light should go out. Return the A SWEEP

MODE switch to AUTO TRIG.

External Horizontal

42. Connect the Calibrator signal to both the Channel 2

INPUT and EXT HORIZ (B EXT TRIG lNPUT] connectors. Set

the B SOURCE switch to EXT, B COUPLING switch to DC and the HORIZ DISPLAY switch to EXT HORIZ. lncrease the

INTENSITY control setting until the display is visible (two dots

displayed diagonally). The display should be five divisions vertically and about 3.7 divisions horizontally. Set the B

10. The display should be reduced ten times horizontally. The display can be positioned horizontally with the horizontal POSITION or FINE control and vertically with the Channel 2 POSITION control.

43. Connect the Calibrator signal to both the Channel 1 and 2 INPUT connectors. Set the TRIGGER switch to CH 1 ONLY and the B SOURCE switch to INT.

44. The display should be five divisions vertically and horizontally.

The display can be postioned horizontally

with the Channel 1 POSITION control and vertically with the

Channel 2 POSITION control.

45. Change the CH1 VOLTS/DIV switch to 5. The display play is reduced to two divisions horizontally. Now set the CH 2 VOLTS/DIV switch to 5. The display is reduced to two divisions vertically.

Trace Finder

46. Set the CH 1 and CH 2 VOLTS/DlV switches to 10

mv. The display i

S not visible since it exceeds the scan area

of the CRT.

47. Press the TRACE FINDER button. Note that the disis returned to the display area. While holding the

play TRACE FINDER button depressed, increase the vertical and horizontal deflection factors until the display is reduced to about two divisions vertically ond horizontally. Adjust the Channel 1 and 2 POSITION controls to center the display

about the center lines of the graticule. Release the TRACE

FINDER and note that the display remains within the viewing area. Disconnect the applied signal.

48. Reduce the INTENSITY control setting to normal, B SOURCE switch to INT and set the HORIZ DISPLAY switch to A.

Z-Axis Input

49. If an, External signal is available (five volts peak to peak minimum] the function of tlhe Z AXIS INPUT circuit can be demonstrated. Connect the external signal to both the

Channel 2 INPUT connector and the Z AXIS INPUT binding posts. Set the A TIME/DIV switch to display about five cycles of the waveform. The positive peaks of the waveform should be blanked and the negative peaks intensified, indi-

cating intensify modulation.

50. This completes the basic operating procedure for the

Type 453. lnstrument operation not explained here, or operations which need further explanation are discussed under General Operating Information.

CONTROL SETUP CHART

Fig. 2-5 shows the front, side and rear panels of the Type

453. This chart can, be reproduced and used as a test-setup record for special measurements, applications or procedures, or it may be used as a training aid for familiarization with this instrument.

GENERAL OPERATING INFORMATION

Intensify Control

The setting of the INTENSITY control may affect the correct focus of the display. Slight readjustment of the FOCUS control may be necessary when the intensity level is changed.

To protect the CRT phosphor, do not turn the INTENSITY control higher than necessary to provide a satisfactory dis-

play. The light filters reduce the observed light output from

the CRT. When using these filters, avoid odvancing the

INTENSITY control to a setting that may bum the phosphor.

When Ihe highest intensity display is desired, remove the filters and use the clear faceplate protector. Also, be careful that the INTENSITY control is not set too high when changing the TIME/DlV switch front a fast to a slow sweep

rate, or when changing the HORIZ DISPLAY switch from EXT HORIZ operation to the norrmal sweep mode.

Astigmatism Adjustment

If a well-defined trace cannot be obtained with the FOCUS

control, adjust the ASTIG adjustment (side panel) as fol-

lows.

2-8

TM 11-6625-1722-15

Fig. 2-5. Control setup chart for the Type 453.

2-9

TM 11-6625-1722-15

NOTE

To check for proper setting of the ASTIG adjustment, slowly turn the FOCUS control through the optimum setting. If the ASTIG adjustment is cor-

rectly set, the vertical and horizontal portions of the trace will come into sharpest focus at the same position of the FOCUS control. This setting of the ASTIG adjustment should be correct for any display. However, it may be necessary to reset the FOCUS control slightly when the INTENSITY control is changed.

1. Connect a 1 V Calibrator signal to either channel and set the VOLTS/DIV switch of that channel to present a twodivision display. Set the MODE switch to display the chan-

nel selected.

2. Set the TIME/DIV switch to .2 ms

3. With the FOCUS control and ASTIG adjustment set to

midrange, adjust the INTENSITY control so the rising portion

of the display can be seen.

4. Set the ASTIG adjustment so the horizontal and vertical portions of the display are equally focused, but not

necessarily well focused.

5. Set the FOCUS control so the vertical portion of the

trace is as thin as possible.

6. Repeat steps 4 and 5 for best overall focus. Make final

check at normal intensity.

Graticule

The graticule of the Type 453 is internally marked on the faceplate of the CRT to provide accurate, no-parallax measurements. The graticule is marked with six vertical and 10 horizontal divisions. Each division is 0.8 centimeter square. In addition, each major division is divided inta five minor divisions at the center vertical and horizontal lines. The

vertical gain and horizontal timing are calibrated to the

graticule so accurate measurements can be made from the CRT. The illumination of the graticule lines can be varied with the SCALE ILLUM control.

Fig. 2-6 shows the graticule of the Type 453 and defines the various measurement lines. The terminology defined here will be used in all discussions involving graticule measurements.

Fig. 2-6. Definition of measurement lines on Type 453 graticule.

remove the filter, press

down at the bottom of the frame

and pull the top of the filter away from the CRT faceplate

(see Fig. 2-7).

The tinted light filter minimizes light reflections from the face of the CRT to improve contrast when viewing the display under high ambient light conditions. A clear plastic faceplate protector is also provided with this instrument for use when neither the mesh nor the tinted filter is used. The clear faceplate protector provides the best display for waveform photographs. It is also preferable for viewing high writing rate displays.

A filter or the faceplate protector should be used at all times ta protect the CRT faceplate from scratches. The faceplate protector and the tinted filter mount in the same holder.

Trace Alignment Adjustment

If a free-running trace is not parallel to the horizontal

graticule lines, set the TRACE ROTATION adjustment as fol-

lows. Position the troce to the center horizontal line. Adjust

the TRACE ROTATION adjustment (side panel) so the trace

is parallel with the horizontal graticule lines.

Light Filter

The mesh filter provided with the Type 453 provides shielding against radiated EMI (electro-magnetic interference) from the face of the CRT. It also serves as a light filter to make the trace more visible under ambient light conditions. To

2-10

Fig. 2-7. Removing the filter or faceplate protector.

TM 11-6625-1722-15

To remove the light filter or faceplate protector from the

holder, press it out to the rear. They can be replaced by snapping them back into the holder.

Trace Finder

The TRACE FINDER provides a means af locating a display which overscans the viewing area either vertically or horizontally. When the TRACE FINDER button is pressed, the display is compressed within the graticule area. T

O locate

and reposition an overscanned display, use the following

procedure.

1. Press the TRACE FINDER button.

2. While the TRACE FINDER button is held depressed, increase the vertical and horizontal deflection factors until the vertical deflection is reduced to about two divisions and the horizontal deflection is reduced to about four divisions (the horizontal deflection needs to be reduced only when in the external horizontal mode of operation).

3. Adjust the vertical and horizontal POSITION controls to center the display about the vertical and horizontal cen-

ter lines.

4. Release the TRACE FINDER button; the display should

remain within the viewing area.

Vertical Channel Selection

Either of the input channels can be used for single-trace displays. Apply the signal to the desired INPUT connector and set the MODE switch to display the channel used. However, since CH 1 ONLY triggering is provided only in Chan-

nel 1 and the invert feature only in Channel 2, the correct channel must be selected to take advantage of these features. For dual-trace displays, connect the signals to both

INPUT connectors and set the MODE switch to one of the dual-trace positions.

Vertical Gain Adjustment

To check the gain of either channel, set the VOLTS/DIV

switch to 20 mV. Set the CALIBRATOR switch to .1 V and

connect the 1 kHz CAL connector to the INPUT of the chan-

nel used. The vertical deflection should be exactly five divisions.

If not, adjust the front-panel GAIN adjustment

for exactly five divisions of deflection.

NOTE

If the gain of the two channels must be closely matched (such as for ADD mode operation), the ADJUSTMENT procedure given in the Calibration section should be used.

The best measurement accuracy when using probes is provided if the GAIN adjustment is made with the probes installed (set the CALIBRATOR switch to 1 V). Also, to provide the most accurate measurements, calibrate the vertical gain

of the Type 453 at the temperature at which the measurement

is to be made.

Step Attenuator Balance

To check the step attenuator balance of either channel, set the Input Coupling switch to GND and set the A SWEEP

MODE swich to AUTO TRIG to provide a free-running trace. Change the VOLTS/DIV switch from 20 mV to 5 mV. If the trace moves vertically, adjust the front-panel STEP ATTEN

BAL adjustment as follows (allow at least 10 minutes warm up before performing this adjustment].

1. With the Input Coupling switch set to GND and the

VOLTS/DIV switch set to 20 mV, move the trace to the center

horizontal line of the graticule with the vertical POSITION control.

2. Set the VOLTS/DIV switch to 5 mV and adjust the STEP ATTEN BAL adjustment to return the trace to the center horizonal line.

3. Recheck step attenuator balance and repeat adjustment until no trace shift occurs as the VOLTS/DIV switch is changed from 20 mV to 5 mV.

Signal Connections

In general, probes offer the most convenient means of connecting a signal to the input of the Type 453. The Tektronix probes are shielded to prevent pickup of electrostatic interference. A 10X attenuator probe offers a high input impedance and allows the circuit under test to perform very close to normal operating conditions. However, a 10X probe

also attenuates the input signal 10 times.

The Tektronix P6045 Field Effect Transistor probe and accessory power supply offer the same high-input impedance as the 10X probes. However, it is particularly useful since it provides

wide-band operatian while presenting no attenuation (1X

gain) and a low input capacitance. To obtain maximum bandwidth when using the probes, observe the grounding considerations given in the probe manual. The probe-toconnector adapters and the bayonet-ground tip provide the best frequency response. Remember that a ground strap only a few inches in length can produce several percent of ringing when operating at the higher frequency limit of this

system. See your Tektronix, Inc. catalog for characteristics

and compatibility of probes for use with this system.

In high-frequency applications requiring maximum overall bandwidth, use coaxial cables terminated at both ends in their characteristic impedance. See the discussion on coaxial cables in this section for more information.

High-level, low-frequency signals can be connected directly to the Type 453 INPUT connectors with short unshielded leads. This coupling method works best for signals below about one kilohertz and deflection foctors above one volt/ division. When this method is used, establish a common ground between the Type 453 and the equipment under test. Attempt to position the leads away from any source of interference to avoid errors in the display. If interference is excessive with unshielded leads, use a coaxial cable or a probe.

Loading Effect of the Type 453

As nearly as possible, simulate actual operating conditions in the equipment under test. Otherwise, the equipment under test may not produce a normal signal. The 10X attenuator probe and field effect transistor probe mentioned previously offer the least circuit loading. See the probe instruction manual for loading characteristics of the individual probes.

2-11

TM 11-6625-1722-15

When the signal is coupled directly to the input of the

Type 453, the input impedance is about one megohm

paralleled by about 20 pF. When the signal is coupled to the input through a coaxial cable, the effeclive input capacitance depends upon the type and Iength of cable used. See the following discussion for

inforrnation on obtaining

maximum frequency responspe with coaxial cables.

The signal cables used to connect the signal 10 the type 453 INPUT connectors have a Iarge effect on the accuracy of the displayed high-frequency waveform.

To maitain the

high-frequency characteristics of the applied signal, highquality low-loss coaxial cable should be used. The cable should be terminated at the Type 453 INPUT connector in its characteristic impedonce. with differing characteristic impedances,

If it is necessary to use cables

use suitable imped-

ance-matching devices to provide the correct transition, with

minimum loss, from one impedance to the other.

The characteristic impedance, velocity of propagation and nature of signal lOSSeS in a coaxial cable are determined by the physical and electrical characteristics of the cable. Losses caused by energy dissipation in the dielectric are

proportional to the signal frequency. Therefore, much of the high-frequency information in a fast-rise pulse can be lost in only a few feet of interconnecting cable if it is not the correct type. To be sure of the high-frequency response of the system when using cables longer than about five feet, observe the transient response of the Type 453 and the

interconnecting cable with a fast-rise

pulse generator (gen-

erator risetime Iess than 0.5 nanoseconds).

DC components. The pre-charging network incorporated in this unit aII

OWS the input-coupling capacitor to charge to

the DC source voltage level when the Input Coupling switch is set to GND. The procedure for using this feature is as

follows:

1. Before connecting the signal containing a DC component to the Type 453 INPUT connector, set the Input Coupling switch to GND. Then connect the signal to the INPUT connector.

2. Wait about one second for the coupling capacitor to

charge.

3. Set the Input Coupling switch to AC. The trace (display) will remain on the screen and the AC component of the signal can be measured in the normal manner.

Deflection Factor

The amount of vertical deflection produced by a signal is determined by the signal amplitude, the attenuation factor of the probe (if used), the setting of the VOLTS/DIV switch and the setting of the VARIABLE VOLTS/DIV control. The

calibrated deflection factors indicated by the VOLTS/DIV switches apply only when the VARIABLE control is set to the CAL position.

The VARIABLE VOLTS/DIV control provides variable (uncalibrated) vertical deflection between the calibrated settings of the VOLTS/DIV switch. The VARIABLE control

extends the maximum vertical deflection factor of the Type 453 to at least 25 volts/division (10 volts position).

Input Coupling

The Channel 1 and 2 lnput Coupling switches allow a

choice of input caupling. The type of display desired will determine the coupling used.

The DC position can be used for most applications. However, if the DC component of the signal is much larger than the AC component, the AC position vvill probably provide a better display. DC coupling should be used to display AC signals below about 16 heltz as they will be attenuated in

the AC position.

In the AC position, the DC component of the signal is blocked by a capacitor in the input circuit. The low-frequency response in the AC position is about 1.6 hertz (–3 dB

point). Therefore,

some low-frequency distortion can be expected near this frequency limit. Distortion will also appear

in square waves which have low-frequency com-

ponents.

The GND position provides a ground reference at the

input of the Type 453. The signal applied to the input con-

nector is internally disconnected but not grounded. The input circuit is held at ground potential, eliminating the need to externally ground the input to establish a DC ground reference.

The GND position can also be used to pre-charge the coupling capacitor to the average voltage level of the signal applied to the INPUT connector. This allows measurement of only the AC component of signals having both AC and

Dual-Trace Operation

Alternate Mode. The ALT position of the MODE switch

produces a disploy which alternates between Channel 1 and 2 with each sweep of the CRT. Although the ALT mode can be used at all sweep rates, the CHOP mode provides

a more satisfactory display at sweep rates below about 50

microseconds/division. At these slower sweep rates, alternate mode switching becomes visually perceptible.

Proper internal triggering in the ALT mode can be ob-

tained in either the NORM or CH 1 ONLY positions of the

TRIGGER switch. When in the NORM position, the sweep is

triggered from the signal on each channel. This provides a stable display of two unrelated signals, but does not indicate the time relationship between the signals. In the CH 1 ONLY position, the two signals are displayed showing true time relationship. If the signals are not time related, the Channel 2 waveform will be unstable in the CH 1 ONLY position.

Chopped Mode. The CHOP position of the MODE switch

produces a display which is electronically switched between channels. In general, the CHOP mode provides the best display at sweep rates slower than about 50 microseconds/ division, or whenever dual-trace, single-shot phenomena are to be displayed. At faster sweep rates the chopped switching becomes apparent and may interfere with the display.

Proper internal triggering for the CHOP mode is provided with the TRIGGER switch set to CH 1 ONLY. If the NORM position is used, the sweep circuits are triggered from the between-channel switching signal and both waveforms will

2-12

TM 11-6625-1722-15

be unstable. External triggering provides the same result as CH 1 ONLY triggering.

Two signals which are time-related can be displayed in the chopped mode showing true time relationship. If the signals are not time-related, the Channel 2 display will appear unstable. Two single-shot, transient, or random

signals which occur within the time interval determined by

the TIME/DIV switch (10 times sweep rate) can be compared using the CHOP mode. To correctly trigger the sweep for maximum resolution, the Channel 1 signal must precede the

Channel 2 signal. Since the signals show true time relation-

ship, time-difference measurements can be made.

Channel 1 Output and Cascaded Operation

If a lower deflection factor than provided by the VOLTS/ DIV switches is desired, Channel 1 can be used as a wideband preamplifier for Channel 2. Apply the input signal to the Channel 1 INPUT connector. Connect a 50-ohm BNC cable (18-inch or shorter cable for maximum cascaded fre-

quency response) between the CH 1 OUT (side panel) and

the Channel 2 INPUT connectors. Set the MODE switch to CH 2 and the TRIGGER switch to NORM. With both VOLTS/ DIV switches set to 5 mV, the deflection factor will be less than one millivolt/division.

To provide calibrated one millivolt/division deflection factor, connect the .1 volt Calibrator signal to the Channel 1 INPUT connector. Set the CH 1 VOLTS/DIV switch to .1

and the CH 2 VOLTS/DIV switch to 5 mV. Adjust the Channel 2 VARIABLE VOLTS/DIV control to produce a display exactly five divisions in amplitude. The cascaded deflection factor is determined by dividing the CH 1 VOLTS/DIV switch setting by 5 (CH 2 VOLTS/DIV switch and VARIABLE control remain as set above). For example, with the CH 1 VOLTS/ DIV switch set to 5 mV the calibrated deflection factor will be 1 millivolt/division; CH 1 VOLTS/DIV switch set to 10 mV, 2 millivolts/division, etc.

The following operating considerations and basic appli-

cations may suggest other uses for this feature.

1. If AC coupling is desired, set the Channel 1 Input Coupling switch to AC and leave the Channel 2 Input Coupling switch set to DC. When both Input Coupling switches are set to DC, DC signal coupling is provided.

2. Keep both vertical POSITION controls set near mid-

range.

one of the POSITION controls being turned away from

midrange, correct operation can be obtained by keeping

the Channel 2 POSITION control near midrange and using

the Channel 1 POSITION control to position the trace near

the desired locatian. Then, use the Channel 2 POSITION control far exact positioning. This method will keep both

Input Preamps operating in their linear range.

least 25 millivolts/division of CRT display in all CH 1 VOLTS/ DIV switch positions.

DIV control have no effect on the signal available at the CH 1 OUT connector.

ance matching stage with or without voltage gain. The

If the input signal has a DC level which necessitates

3. The output voltage at the CH 1 OUT connectar is at

4. The MODE switch and Channel 1 VARIABLE VOLTS/

5. The Channel 1 Input Preamp can be used as an imped-

input resistance is one megohm and the output resistance is about 50 ohms.

6. The dynamic range of the Channel 1 Input Preamp is equal to about 20 times the CH 1 VOLTS/DIV setting. The CH 1 OUT signal is nominally at 0 volt DC for a 0 volt DC input level [Channel 1 POSITION control centered). The Chanel 1 POSITION control can be used to center the output signal within the dynamic range of the amplifier.

7. If dual-trace operation is used, the signal applied to

the Channel 1 INPUT connector is displayed when Channel

1 is turned on. When Channel 2 is turned on, the amplified

signal is displayed. Thus, Channel 1 trace can be used to monitor the input signal while the amplified signal is dis-

played by Channel 2.

8. In special applications where the flat frequency re-

sponse of the Type 453 is not desired, a filter inserted between the CH 1 OUT and Channel 2 INPUT connector allows the oscilloscope to essentially take on the frequency

response of the filter. Combined with method 7, the input can be monitored by Channel 1 and the filtered signal displayed

by Channel 2.

9. By using Channel 1 as a 5X low-level voltage preamplifier (5 mV position), the Channel 1 signal available at the CH 1 OUT connector can be used for any application

where a low-impedance preamplifier signal is needed. Remember that if a 50-ohm load impedance is used, the signal amplitude will be about one-half.

Algebraic Addition

General. The ADD position of the MODE switch can be

used to display the sum or difference of two signals, for common-mode rejection to remove an undesired signal or for DC offset (applying a DC voltage to one channel to offset the DC component of a signal on the other channel).

The common-mode rejection ratio of the Type 453 is greater than 20:1 at 20 megahertz for signal amplitudes up to eight times the VOLTS/DIV switch setting. Rejection ratios of 100:1 can typically be achieved between DC and 5 megahertz by careful adjustment of the gain of either channel while observing the displayed common-mode signal.

Deflection Factor. The overall deflection in the ADD position of the MODE switch when both VOLTS/DIV switches

are set to the same position is the same as the deflection factor indicated by either VOLTS/DIV switch. The amplitude of an added mode display can be determined directly from the resultant CRT deflection multiplied by the deflection factor indicated by either VOLTS/DIV switch. However, if the CH 1 and CH 2 VOLTS/DIV switches are set to different deflection factors, resultant voltage is difficult to determine from the CRT display. In this case, the voltage amplitude of the resultant display can be determined accurately only if the amplitude of the signal applied to either channel is known.

Precautions.

be observed when using the ADD mode.

1. Do not exceed the input voltage

453.

The following general

precautions should

rating of the Type

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TM 11-6625-1722-15

2. Do not apply signals that exceed on equivalent of about 20 times the VOLTS/DIV switch setting. For example, with a VOLTS/DIV switch setting of .5, the voltage applied to that channel should not exceed about 10 volts. Larger voltages may distort the display.

3. Use vertical POSITION control settings which most nearly position the signal of each channel to mid-screen when viewed in either the CH 1 or CH 2 positions of the MODE switch. This insures the greatest dynamic range for ADD mode operation.

4. For similiar response from each channel, set both Input

Coupling switches to the same position.

Trigger Source

INT. For most applications, the sweep can be triggered

internally. In the INT position of the Triggering SOURCE switch, the trigger signal is obtained from the Vertical

Deflection System. The TRIGGER switch provides further

selection of the internal trigger signal; obtained from the

Channel 1 signal in the CH 1 ONLY position, or from the displayed signal when in the NORM position. For singletrace displays of either channel, the NORM position provides the most convenient operation. However, for dualtrace displays special considerations must be made to provide the correct display. Set Dual-Trace Operation in this section

for dual-trace triggering information.

LINE. The LINE position of the SOURCE switch connects

a sample of the power-line frequency to the Trigger Gen-

erator circuit. Line triggering is useful when the input signal

is time-related to the line frequency. It is also useful for

providing a stable display of a line-frequency component

in a complex waveform.

EXT. An external signal conected to the EXT TRIG INPUT connector can be used to trigger the sweep in the EXT position of the Triggering SOURCE switch. The external signal must be time-related to the displayed signal for a stable display. An external trigger signal can be used to provide a triggered display when the internal signal is too low in amplitude for correct triggering, or contains signal components on which it is not desired to trigger. It is also useful when signal tracing in amplifiers, phase-shift networks, waveshaping circuits, etc. The signal from a single point in the circuit under test can be connected to the EXT TRIG INPUT

connector through a signal probe or cable. The sweep is

then triggered by the same signal at all times and allows amplitude, time relationship or waveshape changes of signals at various points in the circuit to be examined without resetting the trigger controls.

frequency components of the trigger signal which can trigger the sweep.

AC. The AC position blocks the DC component of the trigger signal. Signals with low-frequency components below about 30 hertz are attenuated. In general, AC coupling can be used for most applications. However, if the trigger signal contains unwanted components or if the sweep is to be triggered at a low repetition rate or a DC level, one of the remaining COUPLING switch positions will provide a better display.

The triggering point in the AC position depends on the average voltage level of the trigger signal. If the trigger signals occur in a random fashion, the average voltage level will vary, causing the triggering point to vary also. This shift of the triggering point may be enough so it is impossible to

maintain a stable display. In such cases, use DC coupling.

LF REJ. In the LF REJ position, DC is rejected and signals

below about 30 kilohertz are attenuated. Therefore, the

sweep will be triggered only by the higher-frequency com-

ponents of the signal. This position is particularly useful

for providing stable triggering if the trigger signal contains

line-frequency components. Also, in the ALT position of the MODE switch, the LF REJ position provides the best display

at high sweep rates when comparing two unrelated signals

(TRIGGER switch set to NORM).

HF REJ. The HF REJ position passes all low-frequency signals between about 30 hertz and 50 kilohertz. DC is rejected and signals outside the given range are attenuated. When triggering from complex waveforms, this position is useful for providing stable display of low-frequency components.

DC. DC coupling can be used to provide stable triggering with low-frequency signals which would be attenuated in the AC position, or with low-repetition rate signals. The LEVEL control can be adjusted to provide triggering at the desired DC level on the waveform. When using internal triggering, the setting of the Channel 1 and 2 POSITION controls affects the DC trigger level.

DC trigger coupling should not be used in the ALT dualtrace mode if the TRIGGER switch is set to NORM. If used, the sweep will trigger on the DC level of one trace and then either lock out completely or free run on the other trace. Correct DC triggering for this mode can be obtained with the TRIGGER switch set to CH 1 ONLY.

Trigger Slope

same as described for EXT except that the external triggering signal is attenuated 10 times. Attenuation of high-amplitude external triggering signals is desirable to broaden the range of the Triggering LEVEL control. switch is set to LF REJ, attenuation is about 20:1.

Trigger Coupling

Four methods of coupling the circuits can be selected with switches. Each position permits

2-14

When the COUPLING

trigger signal to the trigger

the Triggering COUPLING

selection or rejection of the

The triggering SLOPE switch determines whether the trigger circuit responds on the positive-going or negative-going portion of the trigger signal. When the SLOPE switch is in the + (positive-going) position, the display starts with the positive-going portion of the waveform; in the - (negativegoing) position, the display starts with the negative-going

portion of the waveform (see Fig. 2-8]. When several cycles of a signal appear in the display, the setting of the SLOPE switch is often unimportant. However, if only a certain

portion of a cycle is to be displayed, correct setting of the SLOPE switch is important to provide a display which starts on the desired slope of the input signal.

TM 11-6625-1722-15

Fig. 2-8. Effects of Triggering LEVEL control and SLOPE switch.

2-15

TM 11-6625-1722-15

Trigger Level

The Triggering LEVEL control determines the voltage level on the trigger signal at which the sweep is triggered. When the LEVEL control is set in the + region, the trigger circuit responds at a more positive point on the trigger signal. When the LEVEL control is set in the - region, the trigger

circuit responds at a more negative point on the trigger signal. Fig. 2-8 illustrates this effect with different settings of the SLOPE switch.

set the LEVEL control, first select the Triggering

To SOURCE, COUPLING and SLOPE. Then set the LEVEL

control fully counterclockwise ond rotate it clockwise until the display starts at the desired point.

High-Frequency Stability

The HF STAB control (A only) is used to provide a stable display of high-frequency signals. If a stable display cannot be obtained using the A LEVEL control (trigger signal must have adequate amplitude), adjust the HF STAB control for minimum horizontal jitter in the display. This control has

little effect with low-frequency signals.

A Sweep Triggered Light

The A SWEEP TRIG’D Iight provides a convenient indication of the condition of the A Triggering circuit. If the A Triggering controls are correctly adjusted with an adequate trigger signal applied, the light is on. However, if the A LEVEL control is misadjusted, the A COUPLING or A SOURCE switches incorrectly set or the trigger signal too low in omplitude, the A SWEEP TRIG’D light will be off. This feature can be used as a general indication of correct triggering. It is particularly useful when setting up the trigger circuits when a trigger signal is available without a trace displayed on the CRT and it al

So indicates that the A

sweep is correctly triggered when operating in the DELAYED SWEEP (B) mode.

signals with repetition rates below about 20 hertz. This mode

provides an indication of an adequate trigger signal as well as the correctness of trigger control settings, since there is no display without proper triggering. Also, the A SWEEP TRIG’D light is off when the A sweep is not correctly triggered.

SINGLE SWEEP. When the signal to be displayed is not repetitive or varies in amplitude, shape or time, a conventional repetitive display may produce an unstable presentation. To avoid this, use the single-sweep feature of the Type

453. The SINGLE SWEEP mode can also be used to photograph a non-repetitive signal.

To use the SINGLE SWEEP mode, first make sure the trigger circuit will respond to the event to be displayed. Set the A SWEEP MODE switch to AUTO TRIG or NORM TRIG and obtain the best possible display in the normal manner (for random signals set the trigger circuit to trigger on a signal which is approximately the same omplitude and frequency as the random signal). Then, set the A SWEEP MODE switch to SINGLE SWEEP and press the RESET button. When the RESET button is pushed, the next trigger pulse initiates the sweep and a single trace will be presented on the screen. After this sweep is complete, the A Sweep Generator is

"locked out" until reset. The RESET light located inside the RESET button lights when the A Sweep Generator circuit has been reset and is ready to produce a sweep; it goes out after the sweep is complete. To prepare the circuit for another single-sweep display, press the RESET button again.

Selecting Sweep Rate

The A AND B TIME/DIV switches select calibrated sweep

rates for the Sweep Generators.

The A and B VARIABLE controls provide continuously variable sweep rates between the settings of the TIME/DIV switches. Whenever the UNCAL A OR B light is on, the sweep rate of either A or B Sweep Generator, or both, is uncalibrated. The light is off when the A VARIABLE (front panel) and B TIME/DIV VARIABLE (side panel) controls are both set to the CAL position.

A Sweep Mode

AUTO TRIG. The AUTO TRIG position of the A SWEEP

MODE switch provides a stable display when the A LEVEL control is correctly set (see Trigger Level in this section] and a trigger signal is available. The A SWEEP TRIG’D light indicates when the A Sweep Generator is triggered.

When the trigger repetition rate is less then about 20

hertz, or in the absence of an adequate trigger signal, the A Sweep Generator free runs to produce a reference trace. When an adequate trigger signal is again applied, the free-running condition ends and the A Sweep Generator is triggered to produce a stable display (with correct A LEVEL control setting.)

NORM TRIG. Operation in the NORM TRIG position when a trigger signal is applied is the same as in the AUTO TRIG position. However, when a trigger signal is not present, the A Sweep Generator remains off and there is no display. The A SWEFP TRIG’D light indicates when the A sweep is triggered. The NORM TRIG mode can be used to display

2-16

The sweep rate of the A Sweep Generator is bracketed by the two black lines on the clear plastic flange of the TIME/DIV switch (see Fig. 2-9). The B Sweep Generator sweep rate is indicated by the dot on the DELAYED SWEEP knob. When the dot on the outer knob is set to the same position as the lines on the inner knob, the two knobs lock together and the sweep rate of both Sweep Generators is changed at the same time.

However, when the DELAYED SWEEP knob is pulled outward, the clear plastic flange is disengaged and only the B Sweep Generator sweep rate is changed. This allows changing the delayed sweep rate wihout changing the delay time determined by the A Sweep Generator.

When making time measurements from the graticule, the area between the first-division and ninth-division vertical lines provides the most linear time measurement (see Fig. 2-10). Therefore, the first and last division of the display should not be used for making accurate time measurements. Position the start of the timing area to the first-division vertical line and set the TIME/DIV switch so the end of the timing area falls between the first- and ninth-division vertical lines.

Fig. 2-9.

TM 11-6625-1722-35

Sweep Magnification

The sweep magnifier expands the sweep ten times. The center division of the unmagnified display is the portion visible on the screen in mognified form (see Fig. 2-11]. Equivalent length of the magnified sweep is about 100 divisions;

any 10 division portion may be viewed by adjusting the

horizontal POSITION control to bring the desired portion onto the viewing area. The FINE position control is particularly useful when the magnifier is on, as it provides position-

ing in small increments for more precise control.

To use the magnified sweep, first move the portion of the display which is to be expanded to the center of the graticule. Then set the MAG switch to X10. The FINE position control can be adjusted to position the magnified display

Fig. 2-11. Operation of sweep magnifier.

as desired. The light located below the MAG switch is on whenever the magnifier is on.

When the MAG switch is set to X10, the sweep rate is determined by dividing the TIME/DIV switch setting by 10. For example, if the TIME/DIV switch is set to

magnified sweep rate is 0.05 microsecond/division. The magnified sweep rate must be used for all time measurements when the MAG switch is set to X10. The magnified sweep rate is calibrated when the UNCAL A OR B light is off.

Delayed Sweep (B)

The delayed sweep (B sweep) is operable in the A INTEN DURING B and DELAYED SWEEP (B) positions of the HORIZ DISPLAY switch. The A sweep rate along with the DELAY-

TIME MULTIPLIER dial setting determines the time that the

B sweep is delayed. Sweep rate of the delayed portion is

determined by the B TIME/DIV (DELAYED SWEEP) switch setting.

In the A INTEN DURING B position, the display will

appear similar to Fig. 2-12A. The amount of delay time between the start of A sweep and the intensified portion is determined by the setting of the A TIME/DIV switch and the DELAY-TIME MULTIPLIER dial.

Fig. 2-10. Area of graticule used for accurate time measurements.

For example, the delay indicated by the DELAY-TIME

MULTIPLIER dial setting shown in Fig. 2-13 is 3.55; this cor-

responds to 3.55 CRT divisions of A sweep. This reading

multiplied by the setting of the A TIME/DIV switch gives the calibrated delay time before the start of the B sweep (see B Sweep Mode which follows). The intensified portion of the display is produced by the B sweep. The length of

2-17

TM 11-6625-1722-15

B SWEEP MODE. The B SWEEP MODE switch provides two modes of delayed sweep operation. Fig. 2-14 illustrates the difference between these t

Wo modes. In the B STARTS

AFTER DELAY TIME position, the B sweep is presented immediately after the delay time (see Fig. 2-14A]. The B sweep is triggered at a selected point on A sweep to provide the delay time (B sweep essentially free running]. Since the delay time is the same for each sweep,

the display appears stable In the TRIGGERABLE AFTER DELAY TIME position, the B sweep operates only when it is triggered (by Trigger Circuits) after the selected delay time (see Fig. 2-14B). The B Triggring controls operate as described in this section.

Delayed Sweep Operation. To obtain a delayed sweep

display use the following procedure.

1. Obtain a stable display with the HORIZ DISPLAY

switch set to A.

2. Set the HORIZ DISPLAY switch to A INTEN DURING

3. Set the B SWEEP MODE switch to the desired setting.

If TRIGGERABLE AFTER DELAY TIME is selected, correct B

Triggering is also necessary,

4. Set the delay time with the A TIME/DIV switch and

the DELAY-TIME MULTIPLIER dial.

Fig. 2-12. (A) A INTEN DURING B display (DELAY-TIME MULTIPLIER, 2.95; A TIME/DIV, .5 ms; B TIME/DIV, 50

SWEEP (B) display.

ps),

(B) DELAYED

this portion is about 10 times the setting of the B TIME/DIV

switch.

When the HORIZ DISPLAY switch is set to DELAYED

SWEEP (B), only the intensified portion as viewed in the A

INTEN DURING B position is displayed on the screen at the sweep rate indicated by the B TIME/DIV switch (see Fig. 2-12B).

Fig. 2-13. DELAY-TIME MULTIPLIER dial. Reading shown: 3.55.

5. Pull the DELAYED SWEEP (B TIME/DIV) knob out and

set to the desired sweep rate.

6. If the TRIGGERABLE AFTER DELAY TIME position is used, check the display for an intensified portion. Absence of the intensified zone indicates that B sweep is not correctly triggered.

7. Set the HORIZ DISPLAY switch to DELAYED SWEEP (B).

The intensified zone shown in the A INTEN DURING B posi-

tion is now displayed at the sweep rate selected by the B

TIME/DIV switch.

Several examples using the delayed sweep feature are

given under Basic Applications in this section.

A Sweep Length.

The A SWEEP LENGTH control is most useful when used with delayed sweep. As the control is rotated counterclockwise from the FULL position, the length of the A sweep decreases (sweep rate remains constant)

until it is about four divisions iong in the counterclockwise

position (not in B ENDS A detent). The B ENDS A position produces a display which ends immediately following B sweep if the B sweep ends before the normal end of A sweep. The A SWEEP LENGTH control is used to increase the repetition rate of delayed sweep displays.

To use the A SWEEP LENGTH control, set the HORIZ DISPLAY switch to A INTEN DURING B and set the delay time and delayed sweep rate in the normal manner. Turn the A SWEEP LENGTH control counterclockwise until the sweep ends immediately following the intensified portion on the display. Now set the HORIZ DISPLAY switch to DELAYED SWEEP (B). This method provides the maximum repetition rate for a given delayed sweep disp!ay. In the B ENDS A position, the maximum delayed sweep repetition rate is maintained automatically.

2-18

TM 11-6625-1722-15

Fig. 2-14. Comparison of the delayed-sweep modes.

display the B sweep is delayed a selected amount of time by A sweep.

(A) B STARTS AFTER DELAY TIME, [B) TRIGGERABLE AFTER DELAY TIME. In each

NOTE

Jitter can be introduced into the display and incorrect displays produced through the wrong usage of the A SWEEP LENGTH control. When

using this control first obtain the best possible

display in the FULL position. Then, set the control for the desired A sweep length. If jitter is evident in the display, readjust the Triggering controls or change the A SWEEP LENGTH control to a position

that does not cause jitter.

External Horizontal Deflection

In some applications, it is desirable to display one signal

versus another (X-Y] rather than against time (internal sweep).

The EXT HORIZ position of the HORIZ DISPLAY switch provides a means for applying an external signal to the horizontal amplifier for this type of display.

Two modes of external horizontal operation are provided. When the TRIGGER switch is set to CH 1 ONLY, the B SOURCE switch to INT and the B COUPLING switch to DC, the horizontal deflection is provided by a signal applied to the Channel 1 INPUT connector. The CH 1 VOLTS/DIV switch setting indicates the calibrated horizontal deflection factor (Channel 1 VARIABLE control in-operative). Center the horizontal POSITION control and use the Channel 1 POSITION control for horizontal positioning.

switch, external horizontal deflection is provided by a signal

2-19

TM 11-6625-1722-15

applied to the EXT HORIZ input connector (B EXT TRIG

INPUT). The signal coupling provided by the B COUPLING switch] can be used to select or reject components of the external horizontal signal (all components of external horizontal signal accepted (in DC position). Using this mode of operation, the horizontal deflection factor is uncalibrated. External horizontal deflection factor is about 270 millivolts/ division in the EXT position of the B SOURCE switch and about 2.7 volts/division in the EXT

A and B Gate

The A and B Gate output connectors (on side panel) provide a rectangular output pulse which is coincident with the sweep time of the respective sweep generator. This rectangu-

lar pulse is about +12 volts in amplitude (into high-impedance loads) with pulse duration the same as the respective sweep.

Intensity Modulation

Intensity (Z-axis) modulation can be used to relate a third item of electrical phenomena to the vertical (Y-axis) and the horizontal (X-axis) coordinates without changing the wave shape. The Z-axis modulating signal applied to the CRT circuit changes the intensity of the displayed waveform to provide this display. "Gray scale" intensity modulation can be obtained by applying signals which do not completely blank the display. Large amplitude signals of the correct polarity will completely blank the display; the sharpest display is provided by signals with a fast rise and fall. The voltage amplitude required depends upon tlhe setting of the INTENSITY control. At normal intensity level, a five-volt peak-to-peak signal produces a visible change in brightness. When the Z AXIS INPUT is not in use, keep the ground strap in place to pre-

vent changes in trace intensity due to extraneous noise.

Time markers applied to the Z AXIS INPUT connector provide a direct time reference on the display. With uncalibrated horizontal sweep or external horizontal mode operation, the time markers provide a means of reading time directly from the display. However, if the time-related to the displayed waveform, display should be used (for internal sweep a stable display.

Calibrator

The one-kilohertz square-wave Calibrator provides a convenient signal source for checking basic vertical gain and sweep timing. However, to provide maximum measurement acuracy, the adjustment procedure given in the Calibration section of this manual should be used. The Calibrator output signal is also very useful for adjusting probe compensation as described in the probe instruction manual. In addition, the calibrator can be used as a convenient signal source for application to external equipment.

Voltage. The Calibrator provides accurate peak-to-peak square wave voltages of 0.1 and 1 volt into a high impedance load. Voltage range is selected by the CALIBRATOR switch on the side panel. Output resistance is about 200 ohms in the 1 V position and about 20 ohms in the 0.1 V

for visible trace modulation

markers are not

a single-sweep

only) to provide

of the Type 453

position. The actual voltage across an external load resistor can be calculated in the same manner as with any series resistor combination (necessary only if the load resistance is less than about 50 kilohms).

Current. The current loop, located on the side panel, provides a five milliampere peak-to-peak square-wave current which can be used to check and calibrate currentmeasuring probe systems. This current signal is obtained by clipping the probe around the current loop. Current is constant through the loop in either position of the Calibrator switch. The arrow above the PROBE LOOP indicates conventional current flow; i.e., from + to -.

Frequency. The Calibrator circuit uses frequency-stable components to maintain accurate frequency and constant duty cycle. Thus the Calibrator can be used for checking the basic sweep timing of the horizontal system.

Wave shape. The square-wave output signal of the Cali-

brator can be used as a reference wave shape when check-

ing or adjusting the compensation of passive, high-resistance

probes. Since the square-wave output from the Calibrator has a flat top, any distortion in the displayed waveform is

due to the probe compensation.

BASIC APPLICATIONS

General

The following information describes the procedure and

technique for making basic measurements with a Type 453

Oscilloscope. These applications are not described in detail

since each application must be adapted to the requirements of the individual measurements. Familiarity with the Type 453 will permit these basic wide variety of uses.

Peak-to-Peak Voltage

To make a peak-to-peak

following procedure:

1. Connect the signal to

2. Set the MODE switch to display the channel used.

3. Set the VOLTS/DIV switch to display about five divi-

sions of the waveform.

4. Set the Input Coupling switch to AC.

For low-frequency signals below about 16 hertz,

use the DC position.

5. Set the A Triggering controls to obtain a stable display. Set the TIME/DIV switch to a position that displays several cycles of the waveform.

6. Turn the vertical POSITION control so the lower portion of the waveform coincides with one of the graticule lines below the center horizontal line, and the top of the waveform is an the viewing area. Move the display with the horizontal POSITION control so one of the upper peaks lies near the center vertical line (see Fig. 2-15).

techniques to be applied to a

Measurements-AC

voltage measurement, use the

either INPUT connector.

NOTE

2-20

TM 11-6625-1722-15

7. Measure the divisions of vertical deflection from peak to peak. Make sure the VARIABLE VOLTS/DlV control is in the CAL position.

NOTE

This technique may also be used to make measure-

ments between two points on the waveform rather

than peak to peak.

8. Multiply the distance measured in step 7 by the VOLTS/

DIV switch setting. Also include the attenuation factor of

the probe, if any.

Example. Assume a peak-to-peak vertical deflection of

4.6 divisions (see Fig. 2-15) using a 10X attenuator probe and a VOLTS/DIV switch setting of .5.

Using the formula:

Volts

Peak to Peak

vertical

= deflection X

(divisions)

VOLTS/DIV

setting

Substituting the given values:

Volts Peak to Peak = 4.6 X 0.5V X 10

The peak-to-peak voltage is 23 volts.

Do not move the vertical POSITION control after

this refer-

ence line has been established.

NOTE

To measure a voltage level with respect to a voltage rather than ground, make the following changes in step 6. Set the Input Coupling switch to DC and apply the reference voltage to the lNPUT connector. Then position the trace to the reference line.

7. Set the Input Coupling switch to DC. The ground reference line can be checked at any time by switching to the GND position (except when using a DC reference voltage).

8. Set the A Triggering controls to obtain a stable display. Set the TIME/DIV switch to a setting that displays several cycles of the signal.

9. Measure the distance in divisions between the reference line and the point on the waveform at which the DC level is to be measured. For example, in Fig. 2-16 the measure-

ment is made between the reference line and point A.

10. Establish the polarity of the signal. If the waveform is above the reference line, the voltage is positive; below the line, negative (when the INVERT switch is pushed in if using Channel 2).

11. Multiply the distance measured in step 9 by the VOLTS/ DIV switch setting. Include the attenuation factor of the

probe, if any.

Fig. 2-15. Measuring peak-to-peak voltage of a waveform.

Instantaneous Voltage Measurements-DC

To measure the DC level at a given point on a waveform,

use the following procedure:

1. Connect the signal to either INPUT connector.

2. Set the MODE switch to display the channel used.

3. Set the VOLTS/DIV switch to display about five divi-

sions of the waveform.

4. Set the Input Coupling switch to GND.

5. Set the A SWEEP MODE switch to AUTO TRIG.

6. Position the trace to the bottom line of the graticule

or other reference line. If the voltage is negative with respect

to ground, position the trace to the top line of the graticule.

Example. Assume that the vertical distance measured is

4.6 divisions (see Fig. 2-16), the waveform is above the reference line, using a 10X attenuator probe and a VOLTS/ DIV setting of 2.

Using the formula:

vertical

distance X polarity X

(divisions]

VOLTS/DIV

setting

Substituting the given values:

Instantaneous

Voltage

=4.6 X +1 X 2V X 10

The instantaneous voltage is +92 volts.

Voltage Comparison Measurements

In some applications it may be necessary to establish a set of deflection factors other than those indicated by the VOLTS/DIV switch. This is useful for comparing signals to a reference voltage amplitude. To establish a new set of deflection factors based upon a specific reference amplitude,

proceed as follows:

1. Apply the reference signal of known amplitude to either INPUT conector. Set the MODE switch to display the channel used. Using the VOLTS/DIV switch and the VARIABLE control, adjust the display for an exact number of divisions. Do not move the VARIABLE VOLTS/DIV control after obtaining the desired deflection.

2-21

TM 11-6625-1722-15

Fig. 2-16. Measuring instantaneous DC voltage with respect to a reference.

2. Divide the amplitude of the reference signal (volts) by the product of the deflection in divisions (established in step 1] and the VOLTS/DIV switch setting. This is the Deflec-

tion Conversion Factor.

Deflection

Conversion =

Factor

3. To establish an Adjusted Deflection Factor at any set-

ting of the VOLTS/DIV switch, multiply the VOLTS/DIV switch setting by the Deflection Conversion Factor established in step 2.

Adlusted

Deflection =

Factor

This Adjusted Deflection Factor applies only to the channel used and is correct only if the VARIABLE VOLTS/DIV control is not moved from the position set in step 1.

4. To determine the peak to peak amplitude of a signal compared to a reference, disconnect the reference and apply the signal to the INPUT connector.

5. Set the VOLTS/ DIV switch to a setting that will provide

sufficient deflection to make the measurement. Do not re-

adiust the VARIABLE VOLTS/DIV control.

6. Measure the vertical deflection in divisions and deter-

mine the amplitude by the following formula:

Adjusted

Deflection = 10V X 1.5 = 15 volts/division

Factor

To determine the peak-to-peak amplitude

signal which produces a vertical deflection

of an applied of 5 divisions,

use the Signal Amplitude formula (step 6):

Signal

Amplitude

=15V x 5 = 75 volts

Time-Duration Measurements

To measure time between two points on a

waveform, use

the following procedure.

1. Connect the signal to either INPUT connector.

2. Set the MODE switch to display the channel used.

3. Set the VOLTS/DIV switch to display about five divi-

sions of the waveform.

4. Set the A Triggering controls to obtain a stable display.

5. Set the TIME/DIV switch to the fastest sweep rate that

displays less than eight divisions between the time measure-

ment points (see Fig. 2-17). (See the topic entitled Selecting

Sweep Rate in this section concerning non-linearity of first

and last divisions of display.)

6. Adjust the vertical POSITION control to move the points between which the time measurement is made to the center horizontal line.

7. Adiust the horizontal POSITION control to center the display within the center eight divisions of the graticule.

8. Measure the horizontal distance between the time measurement points. Be sure the A VARIABLE control is set to CAL.

9. Multiply the distance measured in step 8 by the setting of the TIME/DIV switch. If sweep magnification is used, divide this answer by 10.

Example.

Assume that the distance between the time measurement points is 5 divisions (see Fig. 2-17) and the TIME/DIV switch is set to .1 ms with the magnifier off.

Using the formula:

Time Duration =

Example. Assume a reference signal amplitude of 30 volts, a VOLTS/DIV setting of 5 and a deflection of 4 divisions. Substituting these values in the Deflection Conversion Factor formula (step 2):

Deflection

Conversion =

Factor

Then, with a VOLTS/ DIV switch setting of 10, the Adjusted

Deflection Factor (step 3) is:

2-22

Substituting the given values:

Time Duration =

The time duration is 0.5 milliseconds.

Frequency Measurements

The time measurement technique can also be used to measure the frequency of a signal. The frequency of a periodically-recurrent signal is the reciprocal of the time duration of one cycle.

Fig. 2-17. Measuring the time duration between points on a waveform.

1. Measure the time duration of one cycle of the wave-

form as described in the previous application.

2. Take the reciprocal of the time duration to determine

the frequency.

TM 11-6625-1722-15

example, with a five-division display as shown in Fig. 2-18,

the 10% point is 0.5 division up from the start of the rising portion.

9. Meosure the horizontal distance between the 10% and

90% points. Be sure the A VARIABLE control is set to CAL.

10. Multiply the distance measured in step 8 by the setting

of the TIME/DIV switch. If sweep magnification is used,

divide this answer by 10.

Example.

Assume that the horizontal distance between

the 10% and 90% points is four divisions (see Fig. 2-18)

and the TIME/DIV switch is set to 1 us with the MAG

switch set to X10.

Applying the time duration formula to risetime:

Example. The frequency of the signal shown in Fig. 2-17

which has a time duration of 0.5 milliseconds is:

Frequency =

Risetime Measurements

Risetime measurements employ

basically the same techniques as time-duration measurements. The main difference is the points between which the measurement is mode. The

following procedure gives the basic method of measuring

risetime between the 10% and 90% points of the waveform. Falltime can be measured in the same manner on the trailing

edge of the waveform.

1. Connect the signal to either INPUT connector.

2. Set the MODE switch to display the channel used.

3. Set the VOLTS/DIV switch and the VARIABLE control

to produce a display an exact number of divisions in ampli-

tude.

4. Center the display about the center horizontal line.

5. Set the A Triggering controls to obtain a stable dis-

play.

6. Set the TIME/DIV switch to the fastest sweep rate that displays Iess than eight divisions between thel 10% and 90% points on the waveform.

7. Determine the 10% and 90% points on the rising portion of the waveform. The figures given in Table 2-2 are for the points 10% up from the start of the rising portion

and 10% down from the top of the rising portion (90%

point).

8. Adiust the horizontal POSITION control to move the 10% point of the waveform to the first graticule line. For

Substituting the given values:

Risetime =

The risetime is 0.4 microsecond.

Fig. 2-18. Measuring risetime.

Time-Difference Measurements

The calibrated sweep rate and dual-trace features of the

Type 453 allow measurement of time difference between

two separate events. To meosure time difference, use the following procedure.

2-23

TM 11-6625-1722-15

1. Set the Input Coupling switches to the desired coupling

positions.

2. Set the MODE switches to either CHOP or ALT. In gen-

eral, CHOP is more suitable for low-frequency signals and the ALT position is more suitable for high-frequency signals. More information on determining the mode is given under

Dual-Trace Operation in this section.

3. Set the TRIGGER switch to CH 1 ONLY

4. Connect the reference signal to Channel 1 INPUT and the comparison signal to Channel 2 INPUT. The reference signal should precede the comparison signal in time. Use

coaxial cables or probes which have equal time delay to connect the signals to the INPUT connectors.

5. If the signals are of opposite polarity, pull out the INVERT switch to invert the Channel 2 display (signal may be of opposite polarity due to 180° time difference; if so, take into account in final calculation).

6. Set the VOLTS/DIV switches to produce four-or fivedivision displays.

7. Set the A LEVEL control for a stable display

8. If possible, set the TIME/DIV switch for a sweep rate which shows three or more divisions between the two waveforms.

9. Adlust the vertical POSITION controls to center each waveform (or the points on the display between which the

measurement is made) in relation to the center horizontal line.

10. Adjust the horizontal POSITION control so the Channel 1 (reference) waveform crosses the center horizontal line at a vertical graticule line.

11. Measure the horizontal difference between the Channel

1 wavefarm and the Channel 2 waveform (see Fig. 2-19).

12. Multiply the measured difference by the setting of the TIME/DIV switch. If sweep magnification is used, divide this answer by 10.

Example. Assume that the TIME/DIV switch is set to 50

the MAG switch to X10 and the horizontal difference

between waveforms is 4.5 divisions (see Fig. 2-19). Using the formula:

Fig. 2-19. Measuring time difference between two pulses.

time difference from two different sources (dual-trace) or to measure time duration of a single pulse. See Section 1 for

measurement accuracy.

1. Connect the signal to either INPUT connector. Set the

MODE switch to display the channel used.

2. Set the VOLTS/DIV switch to produce a display about

four divisions in amplitude.

3. Adjust the A Triggering controls for a stable display.

4. If possible, set the A TIME/DIV switch to a sweep rate

which displays about eight divisions between the pulses.

5. Set the HORIZ DISPLAY switch to A INTEN DURING B and the B SWEEP MODE switch to B STARTS AFTER DELAY TIME.

6. Set the B TIME/DIV switch to a A TIME/DIV sweep rate. This produces

setting 1/100 of the

an intensified portion

about 0.1 division in length.

NOTE

Do not change the A LEVEL control setting or the horizontal POSITION control setting in the following steps as the measurement accuracy will

be affected.

Substituting the given values:

Time Delay =

The time delay is 22.5 microseconds.

Delayed Sweep Time Measurements

The delayed sweep mode can be used to make accurate time measurements. The following measurement determines the time difference between two pulses displayed on the same trace.

This application may also be used to measure

2-24

7. Turn the DELAY-TIME MULTIPLIER dial to move the

intensified portion to the first pulse.

8. Set the HORIZ DISPLAY switch to DELAYED SWEEP

(B).

9. Adiust the DELAY-TIME MULTIPLIER dial to move the

pulse (or the rising portion) to the center vertical line. Note

the setting of the DELAY-TIME MULTIPLIER dial.

10. Turn the DELAY-TIME MULTIPLIER dial clockwise until

the second pulse is positioned to this same point (if several

pulses are displayed, return to the A INTEN DURING B position to locate the correct pulse). Again note the dial setting.

11. Subtract the first dial setting from the second and

multiply by the delay time shown by the A TIME/DIV switch. This is the time interval between the pulses.

TM 11-6625-1722-15

Example. Assume the first dial setting is 1.31 and the

second dial setting is 8.81 with the TIME/DIV switch set to

0.2 microsecond (see Fig. 2-20]. Using the formula:

Substituting the given values:

Time Difference = [8.81 – 1.31] X 0.2

The time difference is 1.5 microseconds.

ed display, use the Triggered Delayed Sweep Magnification

procedure.

1. Connect the signal to either INPUT connector. Set the

MODE switch to display the channel used.

2. Set the VOLTS/DIV switch to produce a display about

4 divisions in amplitude.

3. Adjust the A Triggering controls for a stable display.

4. Set the A TIME/DIV switch to a sweep rate which dis-

plays the complete waveform.

5. Set the HORIZ DISPLAY switch ta A INTEN DURING B and the B SWEEP MODE switch to B STARTS AFTER DELAY TIME.

6. Position the start of the intensified portion with the DELAY-TIME MULTIPLIER dial to the part of the display ta be magnified.

7. Set the B TIME/DIV switch to a setting which intensifies the full portion to be magnified. The start of the intensified

trace will remain as positioned above.

8. Set the HORIZ DISPLAY switch to DELAYED SWEEP (B].

9. Time measurements can be made from the display in the conventional manner. Sweep rate is determined by the setting of the B TIME/DIV switch.

10. The apparent sweep magnification can be calculated

by dividing the A TIME/DIV switch setting by the B TIME/DIV

switch setting.

Fig. 2-20. Measuring time difference using delayed sweep.

Delayed Sweep Magnification

The delayed sweep feature of the Type 453 can be used to provide higher apparent magnification than is provided by the MAG switch. The sweep rate of the DELAYED SWEEP (B sweep) is not actually increased; the apparent magnifica-

tion is the result of delaying the B sweep an amount of time selected by the A TIME/DIV switch and the DELAY-TIME MULTIPLIER dial before the display is presented at the sweep

rate selected by the B TIME/DIV switch. The following methods uses the B STARTS AFTER DELAY TIME position to allow the delayed portion to be positioned with the DELAYTIME MULTIPLIER dial. If there is too much jitter in the delay-

Example: The apparent magnification of the display

shown in Fig. 2-21 with an A TIME/DIV switch setting of .1

ms and a B TIME/DIV switch setting of 1

Substituting the given values:

The apparent magnification is 100 times.

Triggered Delayed Sweep Magnification. The delayed sweep magnification method just described may produce too much jitter at high apparent magnification ranges. The

TRIGGERABLE AFTER DELAY TIME position of the B SWEEP

MODE switch provides a more stable display since the delayed display is triggered at the same point each time.

1. Set up the display as given in steps 1 through 7

described above.

2. Set the B SWEEP MODE switch to TRIGGERABLE

AFTER DELAY TIME.

3. Adiust the B LEVEL control so the intensified portion on the trace is stable. (If an intensified portion cannot be obtained, see step 4.)

4. Inability to intensify the desired portion indicates that the B Triggering controls are incorrectly set or the signal does not meet the triggering requirements. If the condition cannot be remedied with the B Triggering controls or by

2-25

TM 11-6625-1722-15

Fig. 2-21. Using delayed sweep for sweep magnification.

Set the VOLTS/DIV switch

four

divisions in omplitude

Adjust the A Triggering controls for a stable display.

Set the A TIME/DIV switch to a sweep rate which dis-

to produce a display about

plays the complete waveform.

5. Set the HORIZ DISPLAY switch to A INTEN DURING B and the B SWEEP MODE switch to B STARTS AFTER DELAY TIME.

6. Position the start of the intensified portion with the

DELAY-TIME MULTIPLIER dial to the part of the display to be magnified.

7. Set the B TIME/DIV switch to a setting which intensifies

the full portion to be magnified. The start of the intensified trace will remain as positioned above.

8. Set the HORIZ DISPLAY switch to DELAYED SWEEP

(B).

9. Time measurements can be made from the display in the

conventional manner. Sweep rate is determined by the setting of the B TIME/DIV switch.

Example. Fig. 2-22 shows a complex waveform as displayed on the CRT. The circled portion of the waveform cannot be viewed in any greater detail because the sweep is triggered by the larger amplitude pulses at the start of the display and a faster sweep rate moves this area of the waveform off the viewing area. The second waveform shows the area of interest magnified 10 times using Delayed Sweep. The DELAY-TIME MULTIPLIER dial has been adjusted so the delayed sweep starts just before the area of interest.

increasing the display amplitude (lower VOLTS/DIV setting), externally trigger B sweep.

5. When the correct portion is intensified, set the HORIZ

DISPLAY switch to DELAYED SWEEP (B). Slight readjustment

of the B LEVEL control may be necessary for a stable dis-

play.

6. Measurement and magnification are as described above.

Displaying Complex Signals Using Delayed Sweep

Complex signals often consist of a number of individual events of differing amplitudes. Since the trigger circuits are sensitive to changes in signal amplitude, a stable display can normally be obtained only when the sweep is triggered by the event(s) having the greatest amplitude. However, this may not produce the desired display of a lower amplitude event which follows the triggering event. The delayed sweep feature provides a means of delaying the start of the B sweep by a selected amount following the event which triggers the A Sweep Generator. Then, the part of the waveform which contains the information of interest can be displayed.

Use the following procedure:

1. Connect the signal to either INPUT connector. Set the

MODE switch to display the channel used.

Pulse Jitter Measurements

In some applications it is necessary to measure the amount

of jitter on the leading edge of a pulse, or jitter between

pulses. Use the following procedure:

1. Connect the signal to either INPUT connector. Set the

MODE switch to display the channel used.

2. Set the VOLTS/DIV switch to display about four divi-

sions of the waveform.

3. Set the A TIME/DIV switch to a sweep rate which dis-

plays the complete waveform.

4. Set the A Triggering controls to obtain as stable a dis-

play as possible,

5. Set the HORIZ DISPLAY switch to A INTEN DURING

B and the B SWEEP MODE switch to B STARTS AFTER DELAY

TIME.

6. Position the start of the intensified portion with the DELAY-TIME MULTIPLIER dial so the pulse to be measured is intensified.

7. Set the B TIME/DIV switch to a setting which intensifies the full portion of the pulse that shows jitter.

8. Set the B SWEEP MODE switch to TRIGGERABLE AFTER DELAY TIME.

2-26

TM 11-6625-1722-15

Fig. 2-23. Measuring pulse jitter.

Delayed Trigger Generator

The B GATE output signal can be used to trigger an external device at a selected delay time after the start of A Sweep. The delay time of the B GATE output signal can be

selected by the setting of the DELAY-TIME MULTIPLIER dial

and A TIME/DIV switch.

Fig. 2-22. Displaying a complex signal using delayed sweep.

9. Adiust the B LEVEL control so the intensified portion is

as stable as possible.

10. Set the HORIZ DISPLAY switch to DELAYED SWEEP (B). Slight readjustment of the B LEVEL control may be necessary to produce as stable a display as possible.

11. Pulse jitter is shown by horizontal movement of the pulse (take into account inherent jitter of Delayed Sweep). Measure the amount of horizontal movement. Be sure both VARIABLE controls are set to CAL.

12. Multiply the distance measured in step 11 by the B TIME/DIV switch setting to obtain pulse iitter in time.

Example.

Assume that the horizontal movement is 0.5

divisions (see Fig. 2-23), and the B TIME/DIV switch setting

Using the formula:

A Sweep Triggered Internally. When A sweep is triggered internally to produce a normal display, the delayed trigger may be obtained as follows.

1. Obtain a triggered display in the normal manner.

2. Set the HORIZ DISPLAY switch to A INTEN DURING

3. Select the amount of delay from the start of A Sweep with the DELAY-TIME MULTIPLIER dial. Delay time can be calculated in the normol manner.

4. Set the B SWEEP MODE switch to B STARTS AFTER DELAY TIME.

5. Connect the B GATE signal to the external equipment.

6. The duration of the B GATE signal is determined by the setting of the B TIME/DIV switch.

7. The external equipment will be triggered at the start of the intensified portion if it responds to positive-going triggers, or at the end of the intensified portion if it responds to negative-going triggers.

A Sweep Triggered Externally. This mode of operation can be used to produce a delayed trigger with or without a corresponding display. Connect the external, trigger signal to the A EXT TRIG INPUT connector and set the A SOURCE switch to EXT. Follow the operation given above to obtain

the delayed trigger.

Substituting the given value:

The pulse iitter is 0.25 microseconds.

Normal Trigger Generator

Ordinarily, the signal to be displayed also provides the trigger signal for the oscilloscope. In some instances, it may be desirable to reverse this situation and have the

oscilloscope trigger the signal source. This can be done

by connecting the A GATE signal to the input of the signal

source. Set the A LEVEL control fully clockwise, A SWEEP

2-27

TM 11-6625-1722-15

MODE switch to AUTO TRIG and adjust the A TIME/DIV

switch for the desired display. Since the signal source is triggered by a signal that has a fixed time relationship to the sweep, the output of the signal source can be displayed on the CRT as though the Type 453 were triggered in the normal manner (this method does not allow selection of trigger level or coupling).

Multi-Trace Phase Difference Measurements

Phase comparison between two signals of the same frequency can be made using the dual-trace feature of the Type 453. This method of phase difference measurement can be used up to the frequency limit of the vertical system. To make the comparison, use the following procedure.

1. Set the Input Coupling switches to the same position,

depending on the type of coupling desired.

2. Set the MODE switch to either CHOP or ALT. In general, CHOP is more suitable for low-frequency signals and the ALT position is more suitable for high-frequency signals. More information on determining the mode is given under Dual-Trace Operation in this section.

3. Set the TRIGGER switch to CH 1 ONLY.

4. Connect the reference signal to the Channel 1 INPUT connector and the comparison signal to the Channel 2 INPUT connector. The reference signal should precede the comparison signal in time. Use coaxial cables or probes which have equal time delay to connect the signals to the INPUT connectors.

5. If the signals are of opposite polarity, pull the INVERT switch out to invert the Channel 2 display. (Signals may be of opposite polarity due to 180° phase difference; if so, take this into account in the final calculation.)

6. Set the CH 1 and CH 2 VOLTS/DIV switches and the VARIABLE VOLTS/DIV controls so the displays are equal and about five divisions in amplitude.

7. Set the triggering controls to obtain a stable display.

8. Set the TIME/DIV switch to a sweep rate which dis-

plays about one cycle of the waveform.

9. Move the waveforms to the center of the graticule with the vertical POSITION controls.

10. Turn the A VARIABLE control until one cycle of the reference signal (Channel 1) occupies exactly eight divisions horizontally (see Fig. 2-24). Each division of the graticule represents 45° of the cycle [360° ÷ 8 divisions = 45°/ division). The sweep rate con be stated in terms of degrees as 45° /division.

11. Measure the horizontal difference between corresponding points on the waveforms.

Substituting the given values:

Phase Difference = 0.6 X 45°

The phase difference is 27°.

High Resolution Phase Measurements

More accurate dual-trace phase measurements can be made by increasing the sweep rate (without changing the A VARIABLE control setting). One of the easiest ways to increase

the sweep rate is with the MAG switch. Delayed sweep mag-

nification may also be used. The magnified sweep rate is

determined by dividing the sweep rate obtained previously

by the amount of sweep magnification.

Fig. 2-24. Measuring phase difference.

Example. If the sweep rate were increased 10 times with

the magnifier, the magnified sweep rate would be 45° /division ÷ 10 = 4.5° /division. Fig. 2-25 shows the same signals as used in Fig. 2-24 but with the MAG switch set to X10. With a horizontal difference of six divisions, the phase difference is:

horizontal

magnified

Phase Difference = difference X sweep rate

(divisions)

(degrees/div)

Substituting the given values:

Phase Difference = 6 X 4.5°.

The phase difference is 27°.

12. Multip!y the measured distance (in divisions) by 45°/ division (sweep rate) to obtain the exact amount of phase difference,

Example. Assume a horizontal difference of 0.6 divisions

with a sweep rate of 45°/division as shown in Fig. 2-24. Using the formula:

2-28

X-Y Phase Measurements

The X-Y phase measurement method can be used to meas-

ure the phase difference between the two signals of the same frequency. This method provides an alternate method of measurement for signal frequencies up to about 100 kilohertz. However, above this frequency the inherent phase

TM 11-6625-1722-15

Fig. 2-26. Phase-difference measurement from an X-Y display.

Fig. 2-25. High resolution phase-difference measurement with increased sweep rate.

difference between the vertical and horizontal systems makes accurate phase measurement difficult. In this mode, one of

the sine-wave signals provides horizontal deflection (X) while the other signal provides the vertical deflection (Y). The phase angle between the two signals can be determined from the Iissajous pattern as follows.

1. Connect one of the sine-wave signals to both the Channel 1 INPUT and the Channel 2 INPUT connectors. (Note: steps 1 through 5 measure inherent phase difference between the X and Y amplifiers to provide a more accurate X-Y phase measurement; not necessary below about 1 kHz).

2. Set the HORIZ DISPLAY switch to EXT HORIZ. Set the TRIGGER switch to CH 1 ONLY and the B SOURCE switch to INT.

3. Position the display to the center of the screen and adjust the VOLTS/DIV switches to produce a display less than 6 divisions vertically (Y) and less than 10 divisians horizontally (X). The CH 1 VOLTS/DIV switch controls the horizontal deflection (X) and the CH 2 VOLTS/DIV switch controls the vertical deflection (Y).

4. Center the display in relation to the vertical graticule line. Measure the distances A and B as shown in Fig. 2-26. Distance A is the horizontal measurement between the two points where the trace crosses the center horizontal line. Distance B is the maximum horizontal width of the display.

5. Divide A by B to obtain the sine of the phase angle

between the two signals.

The angle can then be obtained from a trigonometric table. This is the inherent phase shift of the instrument.

6. Connect the Y signal to Channel 2 INPUT connector.

Repeat steps 2 through 5 to measure phase angle. If the dis-

Fig. 2-27. Phase of lissajous display.

(A) 0° or 360°, (B) 30° or 330°, (C) 90° or 270°, (D) 150° or 210° and (E) 180°.

2-29

TM 11-6625-1722-15

play appears as a diaganal straight line, the two signals are either in phase (tilted upper right to lower left) or 180° out of phase (tilted upper left to lower right). If the display is a circle, the signals are 90° out of phase. Fig. 2-27 shows

the Iissajous displays produced between 0° and 360°. Notice

that above 180° phase shift, the resultant display is the same as at some lower angle.

7. Substract the inherent phase shift from the phase angle

to obtain the actual phase difference.

Example. Assume an inherent phase difference of 2° with

a display as shown in Fig. 2-26 where A is 5 divisions and

B is 10 divisions.

Using the formula:

Substituting the given values:

From the trigonometric tables:

To adjust for the phase difference between X and Y amplifiers, subract the inherent phase shift.

Common-Mode Rejection

The ADD feature of the Type 453 can be used to display signals which contain undesirable components. These undesirable components can be eliminated through commonmode rejection. The precautions given under Algebraic Addition should be observed.

1. Connect the signal containing both the desired and

undesired information to the Channel 1 INPUT connector.

2. Connect a signal similar to the unwanted portion of

the Channel 1 signal to the Channel 2 INPUT connector. For

example, in Fig. 2-28 a line-frequency signal is connected

to Channel 2 to cancel out the line-frequency component of the Channel 1 signal.

3. Set both Input Coupling switches to DC (AC if DC

component of input signal is too large).

4. Set the MODE switch to ALT. Set the VOLTS/DIV

switches so the signals are about equal in amplitude.

5. Set the TRIGGER switch to NORM

6. Set the MODE switch to ADD. Pull the INVERT switch

so the common-mode signals are of opposite polarity.

7. Adjust the CH 2 VOLTS/DIV switch and VARIA8LE con-

trol for maximum cancellation of the common-mode signal.

8. The signal which remains should be only the desired portion of the Channel 1 signal. The undesired signal is cancelled out.

Example. An example of this mode of operation is shown

Substituting the given value:

in Fig. 2-28. The signal applied to Channel 1 contains unwanted line-frequency components (Fig. 2-28A). A corresponding line-frequency signal is connected to Channel 2 (Fig. 2-28B). Fig. 2-28C shows the desired portion of the signal as displayed when common-mode rejection is used.

Fig. 2-28. Using the ADD feature for common-mode rejection. component, (B) Channel 2 signal contains line-frequency only, [C) CRT display using common-mode rejection.

(A) Channel 1 signal contains desired information along with line-frequency

2-30

SECTION 3

CIRCUIT DESCRIPTION

TM 11-6625-1722-15

Introduction

This section of the manual contains a description of the circuitry used in the Type 453 Oscilloscope. The description begins with a discussion of the instrument using the basic block diagram shown in Fig. 3-1. Then each circuit is described in detail using a detailed block diagram to show the interconnections between the stages in each major circuit and the relationship of the front-panel controls to the individual stages.

A complete block diagram is located in the Diagrams

section at the rear of this manual. This block diagram shows the overall relationship between all of the circuits. Complete schematics of each circuit are also given in the Diagrams section. Refer to these diagrams throughout the following circuit description for electrical values and relationship.

BLOCK DIAGRAM

General

The following discussion is provided to aid in understanding the overall concept of the Type 453 before the individual circuits are discussed in detail. A basic block diagram of the Type 453 is shown in Fig. 3-1. Only the basic interconnections between the individual blocks are shown on

this diagram. Each block represents a major circuit within this instrument. The number on each block refers to the complete circuit diagram which is located at the rear of

his manual.

Signals to be displayed on the CRT are applied to either

the Channel 1 INPUT and/or the Channel 2 INPUT con-

nectors. The input signals are then amplified by the Channel 1 Vertical Preamp and/or the Channel 2 Vertical Preamp

circuits. circuit provides attenuation, or switches gain, to provide the indicated deflection factor. Each Vertical Preamp circuit also includes separate position, input coupling, gain, variable attenuation and balance controls. A trigger-pickoff stage in the Channel 1 Vertical preamp circuit supplies a sample of the Channel 1 signal to the Trigger Preamp circuit or the CH 1 OUT connector. The output of both Vertical Preamp circuits is connected to the Vertical Switching circuit. This circuit selects the channel(s) to be displayed. An output signal from this circuit is connected to the Z Axis Amplifier circuit to blank out the between-channel switching transients when in the chopped mode af operation. A trigger-pickoff stage at the output of the Vertical Switching circuit provides a sample of the displayed signal(s) to the Trigger Preamp circuit.

to the Vertical

The VOLTS/DIV switch in each Vertical Preamp

The output of

the Vertical Switching circuit is connected

Output Amplifier through the Delay-Line

Driver stage and the Delay Line. The Vertical Output Amplifier circuit provides the final amplification for the signal before it is connected to the vertical deflection plates of the CRT. This circuit includes the TRACE FINDER switch which compresses the vertical and horizontal deflection within the viewing area to aid in locating an off-secreen display.

The Trigger Preamp circuit provides amplification for the internal trigger signal selected by the TRIGGER switch. This internal trigger signal is selected from either the Channel 1 Vertical Preamp circuit or the Vertical Switching circuit. Output from this circuit is connected to the A Trigger Gen-

erator circuit and the B Trigger Generator circuit.

The A and B Trigger Generator circuits produce an output

pulse which initiates the sweep signal produced by the A or B Sweep Generator circuits. The input signal to the A and B Trigger Generator circuits can be individually selected from the internal trigger signal from the Trigger Preamp circuit, an external signal applied to the EXT TRIG INPUT connector, or a sample of the line voltage applied to the instrument. Each trigger circuit contains level, slope, coupling and source controls.

The A Sweep Generator circuit produces a linear saw-

tooth output signal when initiated by the A Trigger Generator circuit. The slope of the sawtooth produced by the

A Sweep Generator circuit is controlled by the A TIME/DIV

switch. The operating mode of the A Sweep Generator circuit is controlled by the A SWEEP MODE switch. In the AUTO TRIG position, the absence of an adequate trigger signal causes the sweep to free run. In the NORM TRIG

position, a horizontal sweep is presented only when correctly

triggered by an adequate trigger signal. The SINGLE SWEEP position allows one (and only one) sweep to be initiated after the circuit is reset with the RESET button.

The B Sweep Generator circuit is basically the same as the A Sweep Generator circuit. However, this circuit only produces a sawtooth output signal after a delay time determined by the A TIME/DIV switch and the DELAY-TIME MULTIPLIER dial. If the B SWEEP MODE switch is set to

the B STARTS AFTER DELAY TIME position, the B Sweep

Generator begins to produce the sweep immediately following the selected delay time. If this switch is in the TRIG-

GERABLE AFTER DELAY TIME position, the B Sweep Generator circuit does not produce a sweep until it receives a

trigger pulse from the B Trigger Generator circuit after the selected delay time.

The output of either the A or B Sweep Generator circuit is amplified by the Horizontal Amplifier circuit to produce horizontal deflection for the CRT in all positions of the HORIZ DISPLAY switch except EXT HORIZ. This circuit con-

tains a 10 times magnifier to increase the sweep rate ten times in any A or B TIME/DIV switch position. Other horizontal deflection signals can be connected to the Horizontal

3-1

3-2

TM 11-6625-1722-15

Fig. 3-1

TM 11-6625-1722-15

Amplifier by using the EXT-HORIZ mode of operation. When

the B SOURCE switch is set to INT, the X signal is connected to the Horizontal Amplifier circuit through the CH 1 Vertical Preamp circuit, the Trigger Preamp circuit and the B Trigger Generator circuit (HORIZ DISPLAY switch set to EXT HORIZ, B SOURCE switch set to INT and the TRIGGER switch set to CH 1 ONLY). In the EXT or EXT ÷ 10 position of the B SOURCE switch, the X signal is obtained from a signal connected to the B EXT TRIG INPUT or EXT HORIZ connector.

The Z Axis Amplifier circuit determines the CRT intensity

and blanking. The Z Axis Amplifier circuit sums the current

inputs from the INTENSITY control, Vertical Switching circuit (chopped blanking), A and B Sweep Generator circuits (unblinking) and the external Z AXIS INPUT binding post.

The output level of the Z Axis Amplifier circuit controls the

trace intensity through the CRT Circuit. The CRT Circuit provides the voltages and contains the controls necessary for he operation of the cathode-ray tube.

The Power Supply circuit provides the low-voltage power necessary for operation of this instrument. This voltage is distributed to all of the circuits in the instrument as shown by the Power Distribution diagram. The Calibrator circuit produces a square-wave output with accurate amplitude

and frequency which can be used to check the calibration

of the instrument and the compensation of probes. The PROBE LOOP provides an accurate current source for calibration of current-measuring probe systems.

EXT HORlZ, B SOURCE switch set to INT and TRIGGER switch set to CH 1 ONLY). The Channel 1 Vertical Preamp circuit provides control of input coupling, vertical deflection factor, balance, vertical position and vertical gain. It also contains a stage to provide a sample of the Channel 1 input signal to the Trigger Preamp circuit to provide internal triggering from the Channel 1 signal only. Fig. 3-2 shows a detailed block diagram of the Channel 1 Vertical Preamp circuit. A schematic of this circuit is shown on diagram 1 at the rear of this manual.

Input

can be

Coupling

Input

signals applied to the Channel 1 INPUT connector

AC-coupled, DC-coupled or internally disconnected. When the Input Coupling switch, SW1, is in the DC position, the input signal is coupled directly to the Input Attenuator stage. In the AC pasition, the input signal passes through capacitor C1. This capacitor prevents the DC component of the signal from passing to the amplifier. The GND position opens the signal path and the input to the amplifier is connected to ground. This provides a ground reference without the need to disconnect the applied signal from the INPUT connector. Resistor R2, connected across the Input Coupling switch, allows C1 to be precharged in the GND position so the trace remains on screen when switched to the AC position with a high DC level applied.

CIRCUIT OPERATION

General

The following circuit analysis is written around

the detailed

block diagrams which are given for each major circuit. These detailed block diagrams give the names of the individual stages within the major circuits and show how they are

connected together. The block diagrams also show the

inputs and outputs for each major circuit and the relation-

ship of the front-panel controls to the individual stages. The circuit diagrams from which the detailed block diagrams are derived are shown in the Diagrams section of this man-

ual. The names assigned to the individual stages on the detailed block diagrams are used throughout the following discussion.

This section describes the electrical operation and relationship of the circuits in the Type 453. The theory of operation for circuits which are used only in this instrument are described in detail in this discussion. Circuits which are

commonly used in the electronics industry are not described in detail. Instead, references are given to textbooks or other

source material which

describe the complete operation of

these circuits.

CHANNEL

1 VERTICAL PREAMP

General

Input signals for vertical deflection on the CRT can be connected to the channel 1 INPUT connector. In the EXT HORIZ mode of operation, this input signal provides the

horizontal (X-axis] deflection [HORIZ DISPLAY switch set to

Input Attenuator

The effective overall Channel 1 deflection factor of the

Type 453 is determined by the CH 1 VOLTS/DIV switch.

In all positions of the CH 1 VOLTS/DIV switch above 20 mV, the basic deflection factor of the Vertical Deflection System is 20 millivolts per division of CRT deflection. To increase this basic deflection factor to the values indicated on the front panel, precision attenuators are switched into the circuit. In the 5 and 10 mV positions, input attenuation is not used. Instead, the gain of the Feedback Amplifier is changed to decrease the deflection factor (see Feedback Amplifier discussion).

For the CH 1 VOLTS/DIV switch positions above 20 mV,

the attenuators are switched into the circuit singly or in pairs

to produce the vertical deflection factor indicated on the

front panel. These attenuators are frequency-compensated

voltage dividers. For DC and low-frequency signals, they

are primarily resistance dividers and the voltage attenuation is determined by the resistance ratio in the circuit. The reactance of the capacitors in the circuit is so high at low frequencies that their effect is negligible. However, at,

higher frequencies, the reactance of the capacitors decreases and the attenuator becomes primarily a capacitance voltage divider.

In addition to providing constant attenuation at all frequencies within the bandwidth of the instrument, the Input Attenuators are designed to maintain the same input RC characteristics (one megohm X 20 pF) for each setting of the CH 1 VOLTS/DIV switch. Each attenuator contains an adjustable series capacitor to provide correct attenuation at high-frequencies and an adjustable shunt capacitor to

provide correct input capacitance.

3-3

TM 11-6625-1722-15

Input Stage

The Channel 1 signal from the Input Attenuator is con-

nected to the Input Stage through the network C17-C18-

C20-R16-R17-R18-R19-R20-R21. R16, R17 and R20 provide the input resistance for this stage. These resistors are part of the attenuation network at all CH 1 VOLTS/DIV switch positions. Variable capacitor C17 adjusts the basic input time constant for a nominal value of one megohm X 20pF. The divider action of R16-R17-R20 allows about 98% of DC and low-frequency signals to pass to the gate of FET (fieldeffect transistor) Q23A. C18 with the stray capacitance in the circuit forms an AC divider which maintains this same voltage division for high-frequency signals. R18 limits the current drive to the gate of Q23A. Diode D18 protects the circuit by clamping the gate of Q23A at about -12.5 volts if a high-amplitude negative signal is applied to the Channel

1 INPUT connector. Over-voltage protection for high-amplitude positive signals is provided by forward conduction of Q23A. The current path is through R23, L23, D36 ond D37.

FET Q23B is a constant current source for Q23A and also

provides temperature compensation for Q23A. The STEP ATTEN BAL adjustment, R30, varies the gate level of Q23B to provide a zero-volt level at the emitter of Q34 with no signal applied. With a zero-volt level at the emitter of Q34, the trace position will not change when switching between

the 5, 10 and 20 mV positions of the CH 1 VOLTS/DIV switch.

DC and Iow-frequency signals are connected from the source of Q23A to the Feedback Amplifier through R23, L23, Q33 ond R39.

L23 isolates the base of Q33 from the source of FET Q23A, Diodes D34-D35 and D36-D37 limit the dynamic range of the signal at the base of Q33 and prevent the following stages from being damaged by a large voltage swing at the source of Q23A. The signal path for high-frequency signals is through C23, Q43 and C39. High-frequency signals at the emitter of Q43 are connected to the base of Q33 through C38. This allows Q33 to be driven at high frequencies while preventing the base circuitry of Q33 from capacitively loading the input FET, Q23A. C38 is selected to provide the same amplitude AC and DC signal at the hose of Q33. C24 couples high-frequency information to the junction of R25-R26, thereby reducing the loading at the

base of Q43.

Feedback Amplifier

The Feedback Amplifier, Q34 and Q54, changes the overall gain of the Channel 1 Vertical Preamp to provide the cor-

rect deflection factor in the 5 and 10 mV positions of the CH 1 VOLTS/DIV switch. Gain of this stage is determined by the

ratio of R46-R50 to R43, R44 or R45. In the 5 mV position of the CH 1 VOLTS/DIV switch, the network C43A-C43B-C43CC43D-C43E-L43A-R43A-R43C-R43E is connected into the emitter circuit of Q34. The ratio between R46-R50 and R43 provides a gain of obout 10. C43A, C43C, L43A and R43C are adjustable to provide high-frequency peaking for the network. In the 10 mV position, conditions are the same ex-

cept that the network C44A-C44B-C44C-L44A-R44A-R44B-

R44C is connected into the circuit in place of the previous network. The ratio between R46-R50 and R44 provides a gain of about 5 times in this CH 1 VOLTS/DIV switch position. C44A, C44C and R44C provide high frequency peaking for this

network. In the 20 mV and higher CH 1 VOLTS/DIV switch

positions, the gain of the Feedback Amplifier is about 2.5 as established by the ratio between R46-R50 and R45. Ad-

justable capacitor C45A provides high-frequency peaking for the Feedback Amplifier stage. C49 and R49 provide high-frequency damping for the circuit. As mentioned previously, the STEP ATTEN BAL adjustment is set to provide zero volts at the emitter of Q34 when the input is at zero volts. Since there is no voltage difference across the emitter resistors, R43, R44 or R45, changing the value of the resistance does not change the current in the circuit. Therefore, the trace position does not change when switching between the 5 mV, 10 mV and 20 mV positions of the CH 1 VOLTS/DIV switch if the STEP ATTEN BAL control is correctly adjusted.

Vertical position of the trcce is determined by the setting of the POSITION control, R40. This control changes the current into the emitter of Q34, a Iow-lmpedance point, which results in negligible voltage change at this point. However, the change in current from the POSITION control produces a resultant DC voltage at the output of the Feedback Amplifier stoge to change the vertical position of the trace. The CH 1 Position Center adjustment, R55, is adjusted to provide a centered display when the Channel 1 POSITlON control is centered (with a zero-volt DC input level).

Zener diode D53 provides a low-impedance source for Q54. Variable capacitor C54 provides feedback from the

collector to the base of Q54 for amplifier stabtllzation.

The output signal from the Feedback Amplifler stage is connected to the Paraphrase Amplifier stage and the Channel 1 Trigger Pickoff stage.

Channel 1 Trigger Pickoff

The signal at the collector of Q54 in the Feedback Amplifier stage is connected to the Channel 1 Trigger Pickoff stage through D58 and R59. This sample of the Channel 1 input signal provides internal triggering from the Channel 1 signal or X-axis deflection for EXT HORIZ operation. Q63 is conneced as an emitter follower to provide isolation between the Trigger Preamp circuit and the Feedback Amplifier stage. It also provides

a minimum load for the Feedback Amplifier stoge and a low output impedance to the Trigger Preamp circuit. D58 provides thermal compensation for Q63. The CH 1 Trigger DC Level adjustment, R60, adjusts the DC level at the base of Q63 for a zero-volt DC output level from the Trigger Preamp circuit when the Channel 1 trace is centered vertically. Output from the Channel 1 Trigger Pickoff stage is connected to the Trigger Preamp circuit through the TRIGGER switch, SW230B.

Paraphase Amplifier

The output signal from the Feedback Amplifier stage is

connected to the Paraphase Amplifier stage through the VAR-

IABLE control, R75. When the VARIABLE control is set to the CAL position (fully clockwise), R75 is effectively by-passed and maximum signal current reaches the base of Q84. Switch SW75, ganged with the VARIA8LE control, is open and the UNCAL neon bulb is disconnected. As the VARIABLE control is rotated counterclockwise from the CAL detent, SW75 is closed and the UNCAL light, B75, ignites to indicate that the vertical deflection is uncalibrated. The sig-

nal applied to the base of Q84 is continuously reduced as the VARIABLE control is rotated counterclockwise.

3-4

Fig. 3-2.

TM 11-6625-1722-15

3-5

Fig. 3-3.

TM 11-6625-1722-15

Q84 and Q94 are connected as a common-emitter phase inverter (paraphase amplifier)l to convert the single-ended input signal to a push-pull output signal. Gain of this stage is determined by the emitter degeneration. As the resistance between the emitters of Q84 and Q94 increases, emitter de-

generation increases also to result in less gain through the stage. The GAIN, adjustment, R90, varies the resistance be-

tween the emitters to control the overall gain of the Channel 1 Vertical Preamp.

CHANNEL 2 VERTICAL PREAMP

General

The Channel 2 Vertical Preamp circuit is basically the same as the Channel 1 Vertical Preamp circuit. Only the differences between the two circuits are described here. Portions of this circuit not described in the following description operate in the same manner as for the Channel 1 Vertical

Preamp circuit [corresponding circuit numbers assigned in the

100-199 range]. Fig. 3-3 shows a detailed block diagram of the Channel 2 Vertical Preamp circuit. A schematic of this circuit is shown in diagram 3 at the rear of this manual.

Feedback Amplifier

Basically, the Channel 2 Feedback Amplifier operates as

described for Channel 1. However, the Channel 2 Vertical

Lloyd P. Hunter (ed.),

second edition, McGraw-Hill, New York, pp. 11-94.

“Handbook of Semiconductor Electronics”,

Preamp circuit does not have a trigger pickoff stage. To provide a load at the collector of Q154 similar to the Ioc the Channel 1 Trigger Pickoff stage provides at the collect of Q54, C159 and R159 are connected into the circuit.

Paraphase Amplifier

The basic Channel 2 Paraphase Amplifier configuratic

and operation is the same as for Channel 1. However, the

INVERT switch, SW195, has been added in the Channel 2 circuit. This switch allows the displayed signal from Channel 2 to be inverted.

VERTICAL SWITCHING

General

The Vertical Switching circuit determines if the CH 1 and/

or the CH 2 Vertical Preamp output signal is connected to

the Vertical Output Amplifier circuit (through the Delay Line Driver and Delay Line stages). In the ALT and CHOP positions of the MODE switch, both channels are alternately displayed on a shared-time basis. Fig. 3-4 shows a detailed block diagram of the Vertical Switching circuit. A schematic

of this circuit is shown on diagram 5 at the rear of this man-

ual.

Diode Gates

The Diode Gates, consisting of four diodes each, can be

thought of as switches which allow either of the Vertical

3-6

Fig. 3-4.

TM 11-6625-1722-15

Preamp output signals to be coupled to the Vertical Output Amplifier. D201 through D204 control the Channel 1 output and D206 through D209 control the Channel 2 output. These diodes are in turn controlled by the Switching Multivibrator for dual-trace displays, or by the MODE switch for singletrace displays.

CH 1. In the CH 1 position of the MODE switch, -12 volts is applied to the junction of D207-D208 in the Channel 2 Diode Gate through R227 (see simplified diagram in Fig. 3-5]. This forward biases D207-D208 and reverse biases D206-D209 since the input to the Delay-Line Driver stage is at about -5.8 volts. D206-D209 block the Channel 2 signal so it cannot pass to the Delay-Line Driver stage. At the same time, in the Channel 1 Diode Gate, D202-D203 are cannected to ground through R212. D202-D203 are held reverse biased while D201-D204 are forward biased. Therefore, the Channel 1 signal posses to the Delay-Line Driver stage.

CH 2. In the CH 2 position of the MODE switch, the above conditions are reversed. D202-D203 are connected to -12 volts through R217 and D207-D208 are connected to ground through R222. The Channel 1 Diode Gate blocks the signal

and the Channel 2 Diode Gate allows it to pass.

Switching Multivibrator

ALT. In this mode of operation, the Switching Multivibra-

tor operates as a bistable multivibrator.

In the ALT position of the MODE switch, -12 volts is applied to the emitter of the Alternate Trace Switching Amplifier stage, Q234 by the MODE switch. Q234 is forward biased to supply current to the "on" Switching-Multivibratar transistor through R235, D235 and R218 or R228. For example if Q225 is conducting, current is supplied to Q225 through R228. The current flow through collector resistors R212 and R222 drops the D207D208 cathode level negative so the Channel 2 Diode Gate is blocked as for Channel 1 only operation. The signal passes through the Channel 1 Diode Gate to the Delay-Line Driver stage.

The alternate trace sync pulse is applied to Q234 through D231 at the end of each sweep. This negative-going sync pulse momentarily interrupts the current through Q234 and both Q215 and Q225 are turned off. When Q234 turns on again after the alternate-trace sync pulse, the charge on C218 determines whether Q215 or Q225 conducts. For example, when Q225 was conducting, C218 was charged negatively on the D228 side to the emitter level of Q225 and positively on the D218 side. This charge is stored while Q234

is off and when current flow through Q234 resumes, this stored charge holds the anode of D228 more negative than the anode of D218. D218 is forward biased and the emitter of Q215 is pulled more negative than the emitter of Q225

ta switch the multivibrator. The conditions described pre-

viously are reversed;

now the Channel 1 Diode Gate is

reverse biased and the Channel 2 signal passes through the

Channel 2 Diode Gate.

The Reference Feedback stage, Q253, provides commonmode voltage feedback from the Delay-Line Driver stage to

allow the diode gates to be switched with a minimum ampli-

tude switching signal. The emitter level of Q253 is connetted to the junction of the Switching Multivibrator collector

Jacob Millman and Herbert Taub,

Waveforms” McGraw-Hill, New York, 1965, pp. 362-389.

“Pulse, Digital and Switching

resistors, R211-R212 and R221-R222 through D213 or D223. The collector level of the "on" Switching Multivibrator transistor is negative and either D213 or D223 is forward biased.

This clamps the cathode level of the forward-biased shunt diodes in the applicable Diode Gate about 0.5 volts more

negative than the emitter level of Q253. The shunt diodes

are clamped near their switching level and therefore they

can be switched very fast with a minimum amplitude switching signal. The level at the emitter of Q253 follows the average voltage level at the emitters of the Delay-Line Driver stage. This maintains about the same voltage difference across the Diode Gate shunt diodes so they can be switched with a minimum amplitude switching signal regardless of the deflection signal at the anodes of the shunt diodes.

CHOP. In the CHOP positian of the MODE switch, the

Switching Multivibratar free runs as an astable multivibrator

at about a 500-kHz rate. The emitters of Q215 and Q225

are connected to -12 volts through R218 and R228. At the time of turn-on, one of the transistors begins to conduct; for example, Q225. Q225 conducts the Channel 2 current and prevents the Channel 2 signal from reaching the Delay-Line Driver stage. Meanwhile, the Channel 1 Diode Gate passes the Channel 1 signal to the Delay-Line Driver.

The frequency-determining components in the CHOP mode are C218-R218-R228. Switching action occurs as follows: When Q225 is on, C218 attempts to charge to -12 volts through R218. The emitter of Q215 slowly goes toward -12 volts as C218 charges. The base af Q215 is held at a nega-

tive point determined by voltage divider R215-R224 between

-12 volts and the collector of Q225. When the emitter volt-

age of Q215 reaches a level slightly more negative than its

base, Q215 conducts. The collector level of Q215 goes

negative and pulls the base of Q225 negative also, through divider R214-R225, to cut Q225 off. When Q215 turns on, its emitter is pulled positive along with C218. This action switches the Diode Gate stage to connect the opposite half to the Delay-Line Driver stage. Again C218 begins to charge towards -12 volts but this time through R228. The emitter of Q225 slowly goes negative as C218 charges, until Q225 turns on. Q215 shuts off and the cycle begins again.

Diodes D218 and D228 have no effect in the CHOP mode. Q253 operates the same in CHOP as in ALT, to allow the Diode Gates to be switched with a minimum signal level.

The Chopped Blanking Amplifier stage, Q244, provides an output pulse to the Z Axis Amplifier which blanks out the transition between the Channel 1 trace and the Channel 2 trace. When the Switching Multivibrator changes states, the current through T241 momentarily changes. A negative pulse is applied to the base of Q244, to turn it off. The width of the pulse at the base of Q244 is determined by R241 and C241. Q244 clips the signal applied to its base, and the positive-going output pulse, which is coincident with trace switching, is applied to the Z Axis Amplifier circuit through R245.

ADD. In the ADD position of the MODE switch, the Diode Gate stage allows both signals to pass to the Delay-Line Driver stage. The Diode Gates are both held on by –12 volts applied to their cathodes through R260 and R270. Since both signals are applied to the Delay-Line Driver stage, the output signal is the algebraic sum of the signals on both Channel 1 and 2.

Ibid., pp. 438-451.

3-7

TM 11-6625-1722-15

Fig. 3-5. Effect of Diode Gates on signal path (simplified Vertical Switching diagram). Conditions shown for CH 1 position of MODE switch.

Delay-Line Driver

Output of the Diode Gate stage is applied to the Delay-

Line Driver stage, Q284 and Q294. Q284 and Q294 are

connected as operational amplifiers with feedback provided by R268-R269 and R278-R279 and the delay-line compensation network. The delay-line compensation network, C261-C262-

C263-C264-C265-C266-R261-R262-R264-R265, provides highfrequency compensation for the Delay Line. R289-C289 in the collector circuit of Q284-Q294 improve the high-frequency reverse termination of the Delay the Delay-Line Driver stage is connected to

Line. Output of

the Vertical Out-

General

The Vertical Output Amplifier circuit provides the final amplification for the vertical deflection signal. This circuit includes the Delay Line and the TRACE FINDER switch. The TRACE FINDER switch compresses an overscanned display

within the viewing area when pressed in. Fig. 3-6 shows a detailed block diagram of the Vertical Output Amplifier circuit. A schematic of this circuit is shown on diagram 6 at the rear of this manual.

VERTICAL OUTPUT AMPLIFIER

put Amplifier through the Delay Line.

Delay Line

Normal Trigger Pickoff Network

The trigger signal for NORM trigger operation is obtained from the collector of Q284. The Normal Trigger DC Level adjustment, R285, sets the DC level of the normal trigger

output signal so the sweep is triggered at the zero-level of

The Delay Line provides approximately 140 nanoseconds delay for the vertical signal to allow the Sweep Generator circuits time to initiate a sweep before the vertical signal reaches the vertical deflection plates. This allows the instrument to display the leading edge of the signal originating the trigger pulse when using internal triggering.

the displayed signal when the Triggering LEVEL control is set to 0. The normal trigger signal is connected to the Trigger Preamp through SW230B. R294 and R295 provide the same DC load for Q294 as provided to Q284 by the Normal Trig-

ger Pickoff Network.

Phase Equalizer Network

The Phase Equalizer Network is comprised of L301-L302L311-C301-C302-C311-C312. This network compensates for

3-8

TM 11-6625-1722-15

Fig. 3-6. Vertical Output Amplifier detailed block diagram.

the phase distortion of the Delay Line. C303-R303 and C313R313 in series with the base-emitter resistance of Q304 and Q314 provide the forward termination for the Delay Line.

Output Amplifier

Q304 and Q314 are connected as common-base ampli-

fiers to provide a low input impedance to properly terminate

the Delay Line (along with the Phase Equalizer Network). It also provides isolation between the Delay Line and the following stages.

The output of Q304 and Q314 is connected to the bases of Q324 and Q334. The network C326-C327-C328-C336R328 provides high-frequency peaking to compensate for the

capacitive loading of the deflection plates on the output stage. C328, C336 and R328 are adjustable to provide opti-

mum response. The TRACE FINDER switch, SW330, reduces the quiescent current of Q324 and Q334, when pressed, to compress an off-screen display within the graticule area. Normally, the collector current for Q324 and Q334 is supplied through R321, R322 and the parallel combination of R323 and R333. When SW330 is pressed, -12-volts is connected to the collector circuit of Q324 and Q334 through R332. This limits the dynamic range of Q324 and Q334 to compress the display vertically within the graticule area. Although the display is nonlinear, it provides a method of locating a signal that is off screen vertically due to incorrect positioning or deflection factor.

Q344 and Q354 amplify the output of Q324 and Q334. The signal at the collectors of Q344 and Q354 is applied to the output transistors, Q364 and Q374, through R344, R354 and T357. D344 and D354 prevent saturation of Q344

and Q354 (to improve the recovery of the Vertical Output

Amplifier circuit) when large signals deflect the display off screen. T357 provides high-frequency balance for the Out-

put Amplifier stage. Q364 and Q374 provide the output sig-

nal voltage to drive the CRT vertical deflection plates. LR367 and LR377 provide damping for the leads connecting the output signal to the deflection plates.

TRIGGER PREAMP

General

The Trigger Preamp circuit amplifies the internal trigger signal to the level necessary to drive the A and B Trigger

Generator circuits. Input signal for the Trigger Preamp circuit is either a sample of the signal applied to Channel 1 or a sample of the composite vertical signal from the Vertical Switching circuit. Fig. 3-7 shows a detailed block diagram of the Trigger Preamp circuit.

A schematic of this circuit is

shown in diagram 7 at the rear of this manual.

Input Circuitry

The internal trigger signal from the Vertical Deflection System is connected to the Trigger Preamp through the TRIGGER switch, SW230B. When the TRIGGER switch is in the NORM position, the trigger signal is a sample

of the composite vertical signal in the Vertical Switching

circuit. This signal is obtained from the collector of Q284 and is a sample of the displayed channel (or channels for dualtrace operation). Since the signal source follows the dualtrace switching stage, the NORM trigger signal also includes the chopped switching transients when operating in the CHOP mode. When the TRIGGER switch is in the NORM position, the CH 1 lights, B400 and B401, are disconnected. Also, the sample of the Channel 1 signal is connected to the CH 1 OUT connector. This output signal can be used to monitor Channel 1 or it can be used to cascade with Channel 2 to provide a one millivolt/division minimum deflection factor (with reduced bandwidth).

In the CH 1 ONLY position of the TRIGGER switch, the internal trigger signal is obtained from the emitter of Q63 in the CH 1 Vertical Preamp circuit. Now, the internal trigger signal is a sample of only the signal applied to the Channel 1 INPUT connector. The CH 1 lights are turned on to indicate that the TRIGGER switch is in the CH 1 ONLY position and the CH 1 OUT connector is disconnected from the circuit.

R402, R403 and R404 terminate the coaxial cables from the trigger pickoff stages to provide a constant load for these stages. In the NORM position of the TRIGGER switch, the NORM trigger signal (from the Vertical Switching circuit) is terminated at the input to the amplifier by R404. The CH 1 ONLY trigger signal (from the CH 1 Vertical Preamp circuit) is terminated at the CH 1 OUT connector by R402. In the CH 1 ONLY position, the CH 1 ONLY trigger signal is terminated at the input to the amplifier by R404 and the NORM trigger signal is terminated by R403.

3-9

TM 11-6625-1722-15

Fig. 3-7. Trigger Preamp detailed diagram

Amplifier Circuitry

The internal trigger signal selected by the TRIGGER switch is connected to the base of Q404. Transistor Q404 converts the trigger voltage signal at its base to a current drive for the remainder of the Trigger Preamp. D408 in the emitter circuit of Q404 provides thermal compensation for the amplifier.

The signal current at the collector of Q404 is connected to the base of Q414, Q413, Q414 and Q423 are connected as a current driven, voltage output operational amplifier. The amplified signal at the collector of Q414 is connected directly to the base of Q413, and to the base of Q423 through zener diode D421 This zener diode provides a DC voltage drop while the signal is connected to the base of Q423 with minimum attenuation. Q413 and Q423 are connected as emitter followers in the complementary symmetry amplifier

configuration. This configuration overcomes the basic Iimitation of emitter followers; inability to provide equal response to

Lloyd P. Hunter, pp. 11-57—-11-62.

3-10

both positive- and negative-going portions of a signal. This is remedied in this configuration by using an NPN transistor for one emitter follower, Q413, and a PNP transistor for the other emitter follower, Q423. Since Q413 is an NPN transistor, it responds best to positive-going signals and Q423, being a PNP transistor responds best to negative-going signals. The result is a circuit which has equally fast response to both positive- and negative-going trigger signals while maintaining a low output impedance. Feedback from the output of the Trigger Preamp circuit is connected to the base of Q414 through R419. This feedback provides more linear operation. Total overall gain of the Trigger Preamp is about 10. The amplified internal trigger signal is connected to the A and B SOURCE switches through R427 and R429.

A TRIGGER GENERATOR

General

The A Trigger Generator circuit produces trigger pulses

to start the A Sweep Generator circuit. These trigger pulses

TM 11-6625-1722-15

Fig. 3-8.

A Trigger Generator detailed block diagram.

are derived either from the internal trigger signal from the Vertical Deflection System, an external signal connected to the EXT TRIG INPUT connector, or a sample of the line volt-

age applied to the instrument. Controls are provided in

this circuit to select trigger level, slope, coupling and source. Fig. 3-8. shows a detailed block diagram of the A Trigger

Generator circuit. A schematic of this circuit is shown on diagram 8 at the rear of this manual.

Trigger Source

The A SOURCE switch, SW430, selects the source of the A trigger signal. Three trigger sources are ovailable; internal, line and external. A fourth position of the A SOURCE switch provides 10 times attenuation for the external trigger signal.

The internal trigger signal is abtained from the Vertical Deflection System through the Trigger Preamp circuit. This signal is a sample of the signal(s) applied to the Channel 1 and/or Channel 2 INPUT connectors. Further selection of the internal trigger source is provided by the TRIGGER switch to provide the internal trigger signal from both channels or from Channel 1 only (see Trigger Preamp discussion for details).

The line trigger is obtained from voltage divider R1104R1105 in the Power Supply circuit. This sample of the line frequency, about 1.5 volts RMS, is coupled to the A Trigger Generator in, the LINE position of the A SOURCE switch. The

A COUPLING switch should not be in the LF REJ position when using this trigger source.

External trigger signals applied to the A EXT TRIG INPUT

connector can be used to produce a trigger in the EXT and

EXT ÷ 10 positions of the A SOURCE switch. Input resistance (DC) is about one megohm in both external positions. However, in the LF REJ position of the A COUPLING switch, the medium and high-frequency resistance drops to about 90

kilohms due to the addition of C436-R436 in the circuit. In the EXT ÷ 10 position, a 10 times frequency compensated attenuator is connected into the input circuit. This attenuator

reduces the input signal amplitude 10 times to provide more A LEVEL control range while maintaining the one-megohm

X 20 pF input RC characteristics.

Trigger Coupling

The A COUPLING switch offers a means of accepting or

reiecting certain frequency components of the trigger signal.

In the AC and LF REJ positions, the DC component of the trigger signal is blocked by coupling capacitors C435 or C436. In the AC position, frequency components below about 30 hertz are attenuated. In the LF REJ position, frequency components below about 30 kilohertz are attenuated.

The HF REJ position attenuates high-frequency components

of the triggering signal. The trigger signal is AC coupled to

the input, attenuating signals below about 30 hertz and above about 50 kilohertz. The DC position provides equal coupling for all signals from DC to 50 megahertz.

3-11

TM 11-6625-1722-15

Input Stage

The trigger signal from the A COUPLING switch is connected to the Input Stage through the network C440-R438R439-R440-R441. R438-R439 provide the input resistance for

this stage. The voltage-divider action of R438-R439 allows about 98% of DC or low frequency signals applied to R438 to be available at the junction of R438 and R439. C440 along

with the stray capacitance in the circuit forms an AC

divider which maintains about this same voltage division

for high-frequency signals. R440 limits the current drive to

the gate of FET Q443. Diode D441 protects the circuit by clamping the gate of Q443 at about -12.5 volts if a high-

amplitude negative signal is applied to the EXT TRIG INPUT

connector. Over-voltage protection for high-amplitude positive signals is provided by the forward conduction of FET Q443.

Q443 is connected as a source follower to provide a high input impedance and a low output impedance. As a result, this stage provides isolation between the A Trigger Generator circuit and the trigger signal source. The output signal from Q443 is connected to the Slope Comparator stage through emitter follower Q453. Diodes D449 and D459 pro-

vide protection for the Slope Comparator stage transistors,

Q454 and Q464.

Slope Comparator

Q454 and Q464 are connected as a difference amplifier

(comparator)

to provide selection of the slope and Ievel at which the sweep is triggered. The reference voltage for the comparator is provided by the A LEVEL control, R460, and the A Trigger Level Center adjustment, R462. The A Trigger Level Center adjustment sets the level at the base of Q464 so the display is triggered at the zero-volt DC level of the incoming trigger signal when the A LEVEL control is centered. The A LEVEL control varies the base level of Q464 to select the point on the trigger signal where triggering occurs.

R458 establishes the emitter current of Q454 and Q464. The transistor with the most positive base controls conduction of the comparator. For example, assume that the trigger signal from the Input Stage is positive going and Q454 is forward biased. The increased current flow through R458

produces a larger voltage drop and the emitters of both Q454 and Q464 go more positive. A more positive voltage at

the emitter of Q464 reverse biases this transistor, since its

base is held at the voltage set by the A LEVEL control, and its collector current decreases. At the same time, Q454 is forward biased and its collector current increases. Notice that the signal currents at the collectors of Q454 and Q464 are oppos~te in phase, The sweep can be triggered from either the negative-going or positive-going slope of the input trigger signal by producing the trigger pulse from either the signal at the collector of Q464 for - slope operation or the signal at the collector of Q454 for + slope operation. This selection is made by the SLOPE switch, SW455.

When the A LEVEL control is set to 0 (midrange], the base of Q464 is at about one volt positive which corresponds to a zero-volt level at the input to this circuit (with correct calibration]. The base-emitter drop af Q464 sets the common emitter level of Q454-Q464 to about +0.3 volts. Since the

5Phillip Cutler, York, pp. 365-372.

“Semiconductor Circuit Analysls”, McGraw-Hill, New

base of Q454 must be about 0.65 volts more positive than the emitter before it can conduct, the comparator switches

around the zero-volt level of the trigger signal (zero-volt

level an the trigger signal corresponds to about one volt positive at this point).

As the A LEVEL control is turned

clockwise toward +, the voltage at the base of Q464

becomes more positive.

This increases the current flow through R458 to produce a more positive voltage on the emitters of both Q454 and Q464. Now the trigger signal must rise more positive before Q454 is biased on. The resultant CRT display starts at a more positive point on the displayed signal. When the A LEVEL control is in the - region, the effect is the opposite to produce a resultant CRT display which starts at a more negative point on the trigger signal.

The slope of the input signal which triggers the A sweep is determined by the A SLOPE switch, SW455. When the A SLOPE switch is set to the – position, the collector of Q454 is connected to the +12-volt supply through D456 and R467. The anode of D466 is grounded and it is reverse biased. Now the collector current af Q464 must flow through D465, R459, the parallel combination D475 and R468-R469L469 and R467 to the + 12-volt supply (see Fig. 3-9). Since the output pulse from the A Trigger Generator circuit is derived from the negative-going portion af the signal applied to the Trigger TD stage, the sweep is triggered on the negative-going portion of the input trigger signal (signal applied to Trigger TD stage is in phase with the input signal for slope triggering). When the A SLOPE switch is set to +, conditions are reversed (see Fig. 3-10). Q464 is connected to the

+12-volt supply through D466 and R467. The anode of

D456 is grounded to divert the collector current of Q454

through the Trigger TD stage. The signal applied to the Trigger TD stage is now 180° out of phase with the input

trigger signal so the sweep is triggered on the positive-going portion of the input signal.

Trigger TD

The Trigger TD stage shapes the output of the Slope Comparator to provide a trigger pulse with a fast leading edge. Tunnel diode D475

is quiescently biased so it operates in its low-voltage state. The current from one of the transistors in the Slope Comparator stage is diverted through the Trigger TD stage by the A SLOPE switch. As this current increases due to a change in the trigger signal, tunnel diode D475 switches to its high-voltage state. L469 opposes the sudden change in current which allows more current to pass through D475 and switch it more quickly. As the current flow stabilizes, L469 again conducts the major part of the current.

However, the current through D475 remains high enough to

hold it in its high-voltage state. The circuit remains in this

condition until the current from the Slope Comparator stage decreases due to a change in the trigger signal applied to

the input. Then, the current through D475 decreases and it reverts to its low-voltage state.

Pulse Amplifier

The trigger signal from the Trigger TD stage is connected to the base of the Pulse Amplifier, Q473, through R472. The trigger pulse at this point is basically a negative-going pulse with a fast rise. The width of the pulse depends upon the

‘Millman and Taub, pp.

452-455.

3-12

TM 11-6625-1722-15

Fig. 3-9.

Trigger path for negative-slope triggering (simplified A Trigger Generator diagram).

waveshape of the input signal and the setting of the A LEVEL control. Q473 is connected as an amplifier with the primary of pulse transformer T474 providing the major collector load. The negative-going pulse at the base of Q473 drives it into heavy conduction and the resulting current increase of Q473 flows through T474, R474, Q473, C473 and C467. Due to the short time constant of the RC network involving C473, the current of Q473 quickly returns to the level determined by R473. The resultant signal at the collector of Q473 is a positive-going fast-rise pulse with the width determined by the time constants of the RC network in the circuit. T474 inverts the output pulse to produce a negativegoing trigger pulse which is coincident with the rise of the output signal from the Trigger TD stage. This negative-going trigger pulse is connected to the A Sweep Generator circuit through C476-R476. D474 limits the collector of Q473 from going more positive than about +0.5 volts. A simulaneous negative-going pulse with the same width as the trigger pulse is available at the emitter of Q473. This pulse is connected to the Auto Pulse Amplifier stage.

Auto Pulse Amplifier

The negative-going trigger pulse from the emitter of Q473 is connected to the base of Q484 through R481. This stage is similar to the Pulse Amplifier stage. Inductor L484 provides the collector load for this stage. The positive-going portion of the trigger pulse is coupled to the Auto Multivibrator stage through D484. D483 clamps the collector of Q484 at about -0.5 volts to eliminate negative transients.

Auto Multivibrator

The basic configuration of the Auto Multivibrator stage is

a monostoble multivibrator

made up of Q485 and Q495. This stage produces the control gate for the auto trigger circuits located in the A Sweep Generator circuit. Under quiescent conditions (no trigger signal), the base of Q495 is

‘Ibid., pp.

405-438.

3-13

TM 11-6625-1722-15

Fig. 3-10.

Trigger path for positive-slope triggering (simplified A Trigger Generator diagram)

near zero volts. The base of Q485 is held at about -0.65 volts by the forward voltage drop of D484. Since the base of Q495 is the most positive, it conducts and raises the emitter level of Q485 positive enough to hold it off. C485 charges to about +13 volts where it is clamped by D486 and D493. The base of Q494 is clamped at about +12.6 volts by D493 which reverse biases it. Since there is no current flow through Q494, its collector level goes negative.

When a trigger signal is present, the positive-going pulses from the Auto Pulse Amplifier stage turn Q485 on through D484. The collector of Q485 goes negative and C485 discharges rapidly through Q485, R490 and R485. As C485 discharges, the current flow through R490 biases Q495 off. When C485 is fully discharged, the current flow through R490 ceases and Q495 comes back on to reset the multi-

vibrator. Now C485 begins to charge towards +75 volts

through R486. Current also flows through R494 and the base of Q494 goes negative to bias it on. The collector level of Q494 rises positive to produce the auto gate output for the A Sweep Generator circuit.

3-14

For low-frequency signals (below about 30 hertz), C485

recharges to about +13 volts in about 85 milliseconds. Then

Q494 is biased off to end the auto gate (display free runs or is unstable). However, if a repetitive trigger signal turns Q485 on again before C485 has charged to +13 volts, C485 is discharged completely again and once more starts to

charge towards +75 volts. Since the base of Q494 remains negative enough with a repetitive trigger signal to hold it in conduction, the auto output level is continuous for a stable

display (with correct A LEVEL control setting).

A SWEEP GENERATOR

General

The A Sweep Generator circuit produces a sawtooth volt-

age which is amplified by the Horizontal Amplifier circuit

to provide horizontal sweep deflection on the CRT. This

output signal is generated on command (trigger pulse) from

the A Sweep Generator circuit. The A Sweep Generator cir-

TM 11-6625-1722-15

Fig. 3-11.

A Sweep Generator detailed block diagram.

cuit also produces on unblanking gate to unblank the CRT

during A sweep time. In addition-this circuit produces several control signals for other circuits within this instrument and several output signals to the side-panel connectors. Fig. 3-11

shows a detailed block diagram of the A Sweep Generotor

circuit. A schematic of this circuit is shown on diagram 9 at

the rear of this manual.

The A SWEEP MODE switch allows three modes of operation. In the NORM TRIG position, a sweep is produced only when a trigger pulse is received from the A Trigger Generator circuit. Operation in the AUTO TRIG position is much

the same as NORM TRIG except that a free-running trace is disployed when a trigger pulse is not present. In the SINGLE SWEEP position, operation is also similar to NORM TRIG except that the sweep is not recurrent. The following circuit description is given with the A SWEEP MODE switch set to NORM TRIG. Differences in operation for the other

two modes are then discussed later.

Normal Trigger Mode Operation

Sweep Gate. The negative-going trigger pulse generated

by the A Trigger Generator circuit is applied to the Sweep

Gate stage through D501. Tunnel diode D505 is quiescently biased on in its low-voltage state. When the negative-going trigger pulse is applied to its cathode, the current through D505 increases and it rapidly switches to its high-voltage state where it remains until reset by the Sweep Reset Multivibrator stage at the end of the sweep. The negative-going level at the cathode of D505 is connected to the base of Q504 through C503 and R503. Q504 is turned on and its

collector goes positive. This positive-going step is connected to the Disconnect Diode through C509-R509 and to the Output Signal Amplifier through C506-R506.

Output Signal Amplifier. The positive-going gate pulse

from the Sweep Gate stage applied to the base of Q514 produces a negative-going pulse at its collector. This pulse is

connected to the Z Axis Amplifier circuit through R519 to unblank the CRT during sweep time. It is also connected to the Holdoff Capacitor through R517 and D517 to discharge it completely at the beginning of each sweep.

The positive-going gate pulse at the base of Q514 is al

coupled from the emitter of Q514 to the emitter of Q524.

The resulting positive-going signal at the collector of Q524

is coupled to the Vertical Switching circuit through C526 to

3-15

TM 11-6625-1722-15

provide an alternate-trace sync pulse for dual-trace operation. It is also coupled to the A GATE output connector on the side panel through R529. D528 and D-529 clamp the gate signal so it does not go more than about 0.5 volts negative and 12.5 volts positive.

Disconnect Diode. The Disconnect Diode, D533, is quiescently conducting current through R506, R508, R509, R530 and R531. The positive-going gate signal from Q504 reverse

biases D533 and interrupts the quiescent current flow. Now

the timing current through the Timing Resistor begins to

charge the Timing Capacitor, C530, so the Sawtaoth Sweep Generator stage can produce a sawtooth output signal. The pasitive-going gate signal also reverse biases D547 to disconnect the Sweep Start Amplifier. The Disconnect Diode is a fast turn-off diode with low reverse leakage to reduce switching time and improve timing linearity at the sfart of the

sweep,

Sawtooth Sweep Generator. The basic generator cir-

cuit is a Miller Integrator circuit.

When the current flow through D533 is interrupted by the Sweep Gate signal, the Timing Capacitor, C530, begins to charge through the Timing Resistor, R530, ond the A Sweep Cal Adjustment, R531. The Timing Capacitor and Resistor are selected by the A TIME/DIV switch to change sweep rate. The A Sweep Cal adjustment allows calibration for accurate sweep timing. The A VARIABLE control, R530Y (see Timing Switch diagram), pravides variable sweep rates by changing the charge time of C530.

The pasitive-going voltage at the R530 side of C530 as

it charges toward +75 volts is connected to the gate of FET Q533. This produces a positive-going output voltage which

is connected to the base of Q531 through R536. Q531 amplifies and inverts the voltage change at its base to produce a negative-going sawtooth output. To provide a linear charging rate for the Timing Capacitor, the sweep output signal is connected to the negative side of C530. This feedback provides a constant charging current for C530 which maintains o constant charge rate to produce a lineor sawtooth output signal. The output voltage continues to go negative until the circuit is reset through the Sweep Reset Multivibrator stage. The output signal from the collector of Q531 is con-

nected to the Horizontal Amplifier circuit through R538 and the Delay Pickoff Comparator stage in the B Sweep Generator circuit through R532.

Sweep Reset Emitter Follower. The negative-going sawtooth voltage at the collector of Q531 is connected to the base of the Sweep Reset Emitter Fallower stage, Q543. The negative-going signal at the emitter of Q543 is coupled to the Sweep Reset Multivibrator stage to determine sweep Iength and to the Sweep Start Amplifier stage to set the starting point for the sweep. D542 connected to the base of

Q543 protects this stage during instrument warmup,

Sweep Start Amplifier. The signal at the emitter of Q543

goes negative along with the applied sawtooth signal. This increases the forward bias on D543 which in turn decreases the forward bias on D545 as the sawtooth goes negative, When the anode of D543 reaches a level about one volt

more positive than the level on the base of Q544, it is

reverse biased to interrupt the current flow through Q544.

The circuit remains in this condition until

retrace is complete. As the voltage at the returns to its original DC level at the end of is again forward biased and Q544 conducts

after the sweep emitter of Q543 the sweep, D545 through D547 to

set the quiescent current through the Disconnect Diode, D533. This establishes the correct starting point for the sweep.

D546 clamps the collector of Q544 at about +0.5 volt. This reduces the voltage swing at the collector of Q544 and improves the response time. The Sweep Start adjustment, R758 (in the B Sweep Generator circuit), sets the base voltage level of Q544. The collector of Q531 is held at this same voltage level through the feedback loop comprised of Q533 ond

Q531, thereby setting the starting point of the sawtooth output signal. The level established by the Sweep Start adjust-

ment is also connected to the B Sweep Start Amplifier so the B sweep starts at the same voltage level as the A sweep.

Sweep Reset Multivibrator. The negative-going sawtooth signal at the emitter of Q543 is coupled to the cathodes of D555 and D556. These diodes are quiescently reverse

biased at the start of the sweep. As the sawtooth voltage at the cathode of D555 goes negative, D555 is forward biased at a level about 0.5 volts more negative than the base level of Q575 (A SWEEP LENGTH cantrol in FULL position). Then the negative-going sawtooth signal from the Sweep Reset Emitter Follower stage is connected to the base of Q575. Q575 and Q585 are connected as a Schmitt bistable multivibratar

. Quiescently, at the start of the sweep, Q585 is conducting and Q575 is biased off to produce a negative level at its collector. This negative level allows the Sweep Gate tunnel diode, D505, to be switched to produce a sweep as discussd previously. When the negative-going sweep signal is connected to the base of Q575 through D555, Q575 is eventually biased on and Q585 is biased off by the emitter coupling between Q575 and Q585. The collector of Q575 rises positive and D505 is switched back to its low-voltage state through R502. D505 is held in its low-voltage state so it cannot accept incoming trigger pulses until after the Sweep Reset Multivibratar stage is reset. This ends the Sweep Gate stage output and the Disconnect Amplifier stage is turned on to rapidly discharge the Timing Capacitor and pull the gate of Q533 rapidly negative to its original level to produce the retrace portion af the sawtooth signal. The Sawtooth Sweep Generator stage is now ready to produce another sweep as soon as the Sweep Reset Multivibrator stage is reset and another trigger pulse is received.

When Q575 is turned on to end the sweep, it remains in conduction for a period of time to establish a holdoff period and allow all circuits to return to their original conditions before the next sweep is produced. The holdoff time is determined by the charge rate of the Holdoff Capacitor, C550. At the start of the sweep, C550 is completely discharged by the unblinking gate at the collector af Q514. It is held at this level throughout the sweep time. When the Sweep Gate output ends, Q514 is cut off and C550 begins to charge toward +75 volts through R552 and R551. The positive-going voltage across he Holdoff Capacitor as it charges is connected to the base of Q575 through D552 and D559. When the base of Q575 rises positive enaugh so it is reverse biased, its collector level drops negative and Q585 comes back into conduction. The bias on the Sweep Gate tunnel diode, D505, returns to a level that allows it to accept the next trigger pulse (D505 is enabled). The Holdoff Capacitor, C550, is

‘I bid., pp, 540-548.

3-16

‘Ibid., pp. 389-394,

TM 11-6625-1722-15

changed by the A TIME/DIV switch for the various sweep rates to provide the correct holdoff time. Diagram 12 shows

a complete diagram of the A TIME/DIV switch.

As the A SWEEP LENGTH control is rotated counterclock-

wise from the FULL position, R555 place as more positive

Level on the anode af D556 than is on the anode of D555 so D555 remains reverse biased. The Sweep Reset Multivibrator is reset as described for FULL sweep length opera-

tion at the point where D556 (instead of D555) is forward biased. Since this occurs at a more positive level on the negative-going sawtooth, the displayed sweep is shorter. Thus, R555 provides a variable sweep length for the A Sweep (from about 11 divisions in the FULL position to about four divisions in the fully clockwise position-not in B ENDS A

detent). In the B ENDS A position (fully counterclockwise), o negative-going pulse from the B Sweep Generator circuit

is connected to the base of Q575 through D575 at the end of the B sweep time. If the A sweep is still running, this negative-going pulse turns Q575 on to end the A sweep also.

Since the A sweep ends immediately following the end of

the B sweep, this position provides the maximum repetition

rate (brightest trace) for Delayed Sweep mode operation.

The HF STAB control, R551, varies the charging rate af the Holdoff Capacitor to provide a stable display at fast sweep rates. This change in holdoff allows sweep synchronization for less display jitter at the faster sweep rates. The HF

STAB control has little effect at slow sweep rates.

Lamp Driver. The auto gate level from the Auto Multivibrator stage in the A Trigger Generatar circuit is connected to the Lamp Driver stage, Q594, through D591 and D594. This gate level is coincident with the trigger pulse generated by the A Trigger Generator circuit and is present

only when the instrument is correctly triggered. The positivegoing auto-gate level saturates Q594 and its collector goes

negative to about zero volts. This applies about 12 volts

across B596, A SWEEP TRIG'D light, and it comes on. This light remains on as long as the auto-gate level is present. When the auto-gate level goes negative because the instru-

ment is no longer triggered, D595 clamps the base level of

Q594 at about –0.5 volt and Q594 is reverse biased. The collector of Q594 rises positive and B596 goes off.

Auto Trigger Mode Operation

Operation of the A Sweep Generator circuit in the AUTO TRIG position of the A SWEEP MODE switch, is the same as for the NORM TRIG position iust described when a trigger pulse is applied. However, when a trigger pulse is not present, a free-running reference trace is produced in the AUTO TRIG mode. This occurs as follows:

The auto-gate level from the Auto Multivibrator stage in the A Trigger Generator circuit is also connected to D592. When the auto-gate level is positive (triggered), the current flowing through D592 and R593 reverse biases D593 and the Sweep Gate tunnel diode, D505, operates as previously described for NORM TRIG operation. However, when the

instrument is not triggered, the auto-gate level drops negative and the reduction in current through D592 and R593 allow D593 to become forward biased. Now, when the Sweep Reset Multivibratar stage resets at the end of the

holdoff period, the additional current from R593-D593

flows through D505 and is sufficient to automatically switch

the Sweep Gate tunnel diode back into its high-voltoge state. The result is that the A Sweep Generator circuit is automatically retriggered at the end of each holdoff period and a free-running sweep is produced. Since the sweep free runs at the sweep rate of the A Sweep Generator circuit (as selected by the A TIME/DIV switch), a bright reference trace is produced even at fast sweep rates.

Single Sweep Operation

General. Operation of the Sweep Generator in the

SINGLE SWEEP position of the A SWEEP MODE switch is similar to operation in the other modes. However, after one sweep has been produced, the Sweep Reset Multivibrator stage does not reset. All succeeding trigger pulses are locked out until the RESET button is pressed.

In the SINGLE SWEEP position, the A SWEEP MODE switch disconnects the charging current for the Holdoff Capacitor. Now, Q575 remains on when it is forward biased through D555 or D556 at the end of the sweep. With Q575 on, D505 is held in its low-voltage state to lock out any incoming trigger pulses. The circuit remains in this condition until reset by the Single-Sweep Reset Amplifier stage.

Single-Sweep Reset Amplifier. The Single-Sweep Reset Amplifier, Q564, produces a pulse to reset the Sweep Reset

Multivibrator stage so another sweep can be produced in

the SINGLE SWEEP mode of operation. Quiescently, Q564 is biased off and the RESET switch is open. When the RESET button is pressed, B568 ignites and the voltage at the base

of Q564 goes negative. Q564 saturates and produces a

positive-going output pulse. This pulse has sufficient amplitude to shut off Q575 and allow Q585 to conduct and enable

the Sweep Gate tunnel diode, D505. Now the A Sweep Generator circuit can be triggered when the next trigger

pulse is received.

Lamp Driver. In the SINGLE SWEEP mode, the cathode of

D591 is connected to ground to block the incoming auto-gate

level. The A SWEEP TRIG'D light, B596 is disconnected from

the collector of Q594 and the RESET light, B597, is connected into the circuit. The anode of D595 is also disconnected from ground. Now the condition of Q594 is determined by the Sweep Reset Multivibratar stage. When Q585 is off before the RESET button is pressed, the collector level of Q585 is negative. The current through R594-D595-R587-R588 sets the base level of Q594 negative enough to bias it off. However, when the RESET button is pressed and Q585 turns on, its collector goes positive. This positive level allows the base of Q594 to go positive also and it is biased on. The collector of Q594 goes negative and the RESET light comes on. Q594 and the RESET light remain on until Q585 turns off again at the end of the next sweep.

TRIGGER GENERATOR

General

The B Trigger Generatar circuit is basically the A Trigger Generator circuit. Only the differences between the two circuits are discussed here. Portions of the circuit not described in the following discussion operate in the same manner as for the A Trigger Generator circuit

the same as

3-17

TM 11-6625-1722-15

Fig. 3-12.

B Trigger Generator detailed block diagram

(corresponding circuit numbers are assigned in the 600-699 range). Fig. 3-12 shows a detailed block diagram of the B Trigger Generator circuit. A schematic of this circuit is shown on diagram 10 at the rear of this manual.

Input Stage

The B Input Stoge operotes in basically the same manner

as described for the A Trigger Generatar circuit. However,

in the B Trigger Generator circuit, the HORIZ DISPLAY switch, SW801A and D638, block the B Trigger Generator input signal in the modes where B triggering is not desired. In the A position of the HORIZ DISPLAY switch, -12 volts is connected to the cathode af D635 and it is forward biased. Since the cathode of D638 is connected to +12 volts through R638, D638 is reverse biased and it blocks the trigger signal. In the A INTEN DURING B and DELAYED SWEEP (B) posiions, a second switch, B SWEEP MODE SW635 determines

whether the B trigger signal is blocked or passed to the Slope Comparator stage. If the B SWEEP MODE switch is in the B STARTS AFTER DELAY TIME position, the trigger signal is blocked as in the A position. However, the B Sweep Generator essentially free runs in this position as controlled

by another portion of the B SWEEP MODE switch located

in the B Sweep Generator circuit (see B Sweep Generator discussion). In the TRIGGERABLE AFTER DELAY TIME position, -12 volts is connected to the cathode of D638 through

R639 rather than to D635. This forward biases D638 and allows the B trigger signal to pass to the B Slope Comparator stage.

In all positions of the HORIZ DISPLAY switch except EXT HORIZ, D641 is back biased since it is connected to +12 volts through R641. In the EXT HORIZ position, D638 is

reverse biased because its cathode rises positive toward

+12 volts applied through R638. Therefore, the trigger signal can not pass through D638. D641 is forward biased by –12 volts connected to its cathode through R642 by SW801A. The signal from the Input Stage is connected to the Horizontal Amplifier through D641 and the External

Horizontal Gain Network, R644-R645-R646. Gain of the

External Horizontal circuit is set by R645, Ext Horiz Gain, so a signal applied to the Channel 1 INPUT connector pro-

duces the indicated horizontal deflection.

The external horizontal signal can be obtained either

externally from the B EXT TRIG INPUT or EXT HORIZ con-

nector when the B SOURCE switch is set to EXT or EXT ÷

10, or internally from Channel 1 when the TRIGGER switch is in the CH 1 ONLY position and the B SOURCE switch is set to INT.

Pulse Amplifier

The Pulse Amplifier in the B Trigger Generator operates much the same as in the A Trigger Generator. However, since there is no Auto circuit in the B Trigger Generator, a pulse is available only at the collector of Q684. The output pulse is applied to the B Sweep Generator through T686 and R688-C688.

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TM 11-6625-1722-15

B SWEEP GENERATOR

General

The B Sweep Generator circuit is basically the same as the A Sweep Generator circuit. Only the differences between the two circuits are discusssd here. The following

circuits operate as described for the A Sweep Generator corresponding circuit numbers assigned in the 700-799 range): Sweep Gate [D705, Q704), Disconnect Diode (D742),

Sawtooth Sweep Generator (Q743 and Q741), Sweep Reset

Emitter Follower (Q753) and the Sweep Start Amplifier

(Q754). Fig. 3-13 shows a detailed block diagram of the B Sweep Generator circuit. A schematic of this circuit is shown

on diagram 11 at the rear of this manual.

Output Signal Amplifier

Basically, the B Output Signal Amplifier is the same as the corresponding circuit in the A Sweep Generator circuit. Two unblanking gates are available from the collector of Q714. An unblanking gate is connected to the Z Axis Amp-

lifier circuit through R717 and the HORIZ DISPLAY switch

to unblank the CRT to display the B sweep. For A INTEN

DURING B operation, additional unblinking current is added to the A unblinking gate during the B sweep time. This produces a display which is partially unblanked during A sweep time and further unblanked during B sweep time to produce a display which has an intensified portion coincident with the B sweep time.

Delay-Pickoff Comparator

The Delay-Pickoff Comparator stage allows selection of

the amount of delay from the start of the A sweep before

the B Sweep Generator is turned on. This stage allows the start of B sweep to be delayed between 0.20 and 10.20 times the setting of the A TIME/DIV switch. Then, the B Sweep

Generatar is turned on and operates at a sweep rate inde-

pendent of the A Sweep Generator (determined by setting of

B TIME/DIV switch).

Q764A and B are connected as a voltage comparator.

In this configuration, the transistor with the most positive

Fig. 3-13.

B Sweep Genercctor detailed block diagram.

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TM 11-6625-1722-15

base controls conduction. A dual transistor, Q764, and a dual diode, D764, provide temperature stability for the comparator circuit. through the conducting transistor. Reference voltage for

the comparator circuit MULTIPLIER control, R760. The voltage to this control is filtered by R759-C759 to hold it constant and allow precise delay pickoff. The instrument is calibrated so that the major dial markings of R760 correspond to the major divisions of horizontal deflection on the graticule. if the DELAY-TIME MULTIPLIER dial is set to 5.00, the B Sweep Generator is delayed five divisions of the A sweep time before it can produce a sweep (B sweep delay time equals five times setting of A TIME/DIV switch).

The output sawtooth from the A Sawtooth Sweep Generator stage is connected to the base of Q764A. The quiescent level of the A sawtooth biases Q764A on and its collector is negative enaugh to hold Q772 in the Delay Multivibrator stage in conduction. As the A sweep output sawtooth begins to run down, the base of Q764A also goes negative. When it goes more negative than Ihe level at the base of Q764B (established by the DELAY-TIME Multiplier control), Q764B takes over conduction of the comparator and Q764A shuts off. This also switches the Delay Multivibratar stage to produce a negative-going reset pulse to the B Sweep Reset Multivibrator.

When the A sweep resets, Q764A is again returned to conduction and Q764B is turned off. This also resets the Delay Multivibrator to produce a positive-going output pulse. If the B sweep is still running, this positive-going pulse forces the B Sweep Reset Multivibrator to reset and end the B sweep also.

Delay Multivibrator

The Delay Multivibrator, Q768 and Q772, provides a

lockout for the B Sweep Generator circuit during the A

Sweep Generator reset and holdoff time to allow accurate delayed-sweep measurements when the DELAY-TIME Multi-

plier dial is set near 0. This stage prevents the B Sweep Generator from being triggered before the A Sweep Gen-

erator is triggered (B Sweep Generator must always be

triggered after the A Sweep Generator is triggered). This

circuit also produces a pulse which resets the B Sweep Reset Multivibrator stage after the delay period so the B Sweep

Gate tunnel diode can be enabled to produce a sweep.

Transistors Q768 and Q772 are connected as a Schmitt

bistable multivibrator. Quiescently, Q772 is held on by the

negative level at the collector of Q764A and Q768 remains off. The circuit remains in this condition until the incoming

A Sweep switches the Delay-Pickoff Comparator (see DelayPickoff Comparator discussion). Then, the base of Q772 goes positive and it turns off. At the same time, the base of Q768 is pulled negative by the collector level of Q764B

and it turns on. The collector of Q772 goes negative and a

negative-going output pulse is coupled to the B Sweep Reset Multivibrator stage through C774. This pulse resets the B Sweep Reset Multivibrator which in turn enables the B

Sweep Gate stage.

Sweep Reset Multivibrator

The basic B Sweep Reset Multivibra!or configuration and

operation is the same as for the A Sweep Generator. How-

Q769 maintains a constant current

is provided by the DELAY-TIME

For example,

ever, several differences do exist. The B Sweep Reset Multivibrator dos not have a sweep length network for variable sweep length or a Holdoff Capacitor and associated circuit to reset the B Sweep Reset Multivibrator after the retrace.

Instead, the negative-going sweep from the B Sweep Reset Emitter Follower, Q753, is connected to the base of Q785 through D748. Diode D748 is forward biased when the

sweep voltage at the emitter of Q753 drops about 0.5 volts, more negative than the level at the base of Q785 established by voltage divider R784-R785 between +12 volts and the collector of Q775. This negative-going sawtooth turns on Q785 and its collector goes positive to switch the B Sweep

Gate tunnel diode, D705 to its low-voltage state, which resets the B Sweep. Q785 remains on and holds the B Sweep Gate tunnel diode locked out until the B Sweep Reset Multivibrator is reset by the Delay Multivibrator.

When the B Sweep Reset Multivibrator is reset by the Delay Multivibrator, Q775 comes on and Q785 turns off. The collector of Q785 goes negative and the B Sweep Gate tunnel diode, D705, is enabled. The state in which D705 remains depends upon the B SWEEP MODE switch and the HORIZ DISPLAY switch. When the B SWEEP MODE switch, SW635, is set to the TRIGGERABLE AFTER DELAY TIME position, D705 is biased so it can be switched to its highvoltage state by the next trigger pulse from the B Trigger Generatar. However, if the B SWEEP MODE switch is set to the B STARTS AFTER DELAY TIME position, the setting of the HORIZ DISPLAY switch, SW801A, determines operation of the B Sweep Gate tunnel diode. In the A position, the B trigger pulses are blocked in the B Trigger Generator circuit so the B Sweep Generator cannot be triggered and does not produce a sweep. In the A INTEN DURING B and DELAYED SWEEP (B) position, -12 volts is connected to the cathode of D705 through R786 and R789. This voltage pulls the cathode of D705 negative enough so that it automatically switches to its high-voltage state after it is enabled by the B Sweep Reset Multivibrator stage. This produces

a free-running B sweep Reset similar to the no trigger AUTO TRIG mode in the A Sweep Generator. However, since

the B Sweep is reset (and automatically retriggered) at a fixed point on the A sweep sawtooth, the display is relatively stable. The best delayed sweep stability is provided in the TRIGGERABLE AFTER DELAY TIME position, since the B sweep is triggered by the trigger signal in this mode.

B Ends A Pulse Amplifier

The positive-going voltage as the B unblanking gate ends is coupled to the B Ends A Pulse Amplifier, Q734, through C731 and D731. When the A SWEEP LENGTH control is in the B ENDS A position, this pulse saturates Q734 to produce a negative-going ouput pulse at its collector. This negative-going pulse is connected to the A Sweep Reset Multivibrator stage to reset the A sweep at the end of the B sweep for maximum delayed sweep repetition rate.

HORIZONTAL AMPLIFIER

General

The Horizontal Amplifier circuit provides the output signal to the CRT horizontal deflection plates. In all positions of the HORIZ DISPLAY switch except EXT HORIZ, the horizontal deflection signal is a sawtooth from either the A Sweep Generator circuit or the B Sweep Generator circuit.

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TM 11-6625-1722-15

Fig. 3-14.

Horizontal Amplifier dotalled block diagram.

In the EXT HORIZ position, the horizontal deflection signal is obtained from the input Stage of the B Trigger Generator. In addition, this circuit contains the horizontal magnifier circuit and the horizontal positioning network. Fig. 3-14 shows a detailed block diagram of the Horizontal Amplifier circuit. A schematic of this circuit is shown on diagram 13

at the rear of this manual.

Input Amplifiers

The input signal for the Horizontal Amplifier is selected by the HORIZ DISPLAY switch, SW801A. In the A and A INTEN DURING B positions of the HORIZ DISPLAY switch, the sawtooth from the A Sweep Generator is connected to the base of the - Input Amplifier, Q814, through R803. In the DELAYED SWEEP (B) position, the B sawtooth is connected to the base of Q814. Whichever sawtooth signal is connected to the base of Q814 produces a current change which is amplified to produce a positive-going sawtooth voltage at the collector. This positive-going sawtooth signal is connected ta the base af Q834 in the Paraphase Amplifier stage.

In the EXT HORIZ position of the HORIZ DISPLAY switch,

the external horizontal signal from the B Trigger Generator

circuit is connected to the base of the + Input Amplifier, Q824, through R821 The A and B sawtooth signals are

grounded by the HORIZ DISPLAY switch. The B SOURCE switch selects either the internal signal from Channel 1 (TRIGGER switch set to CH 1 ONLY) or an external signal connected to the EXT HORIZ connector. When the internal signal is selected, the Channel 1 deflection factor as indicated by the CH 1 VOLTS/DIV switch applies as Horizontal Volts/Division. More information on the external horizontal circuitry is contained in the B Trigger Generator circuit discussion.

Horizontal positioning is provided by the POSITION control, R805A, and the FINE control, R805B, connected to the base of Q814. These controls vary the quiescent DC level at the base of Q814 which in turn sets the DC level at the horizontal deflection plates to determine the horizontal position of the trace.

C804-RB04 eliminate common-mode

noise from the position controls.

Paraphase Amplifier

The output of the + and – Input Amplifier stages is

connected to the Paraphase Amplifier stage, Q834 and Q844.

This stage converts the single-ended input signal from either

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TM 11-6625-1722-15

Input Amplifier stage to a push-pull output signal which is necessary to drive the horizontal deflection plates of the CRT. In all positions of the HORIZ DISPLAY switch except EXT HORIZ, a positive-going sawtooth signal is connected to the base of Q834 through Q814. This produces a negative-going sawtooth valtage at the collector of Q834. At the same time, the emitter of Q834 goes positive and this change is connected to the emitter of Q844 through the gain-setting network, R835-R836-R845-R846. In all positions of the HORIZ DISPLAY switch except EXT HORIZ, no signal is connected to the base of Q844 thraugh Q824 so that Q844 operates as the emitter-driven section of a paraphase amplifier. Then, the positive-going change at its emitter is amplified to produce a positive-gaing sawtooth signal at the

collector. Thus the single-ended input sawtooth signal has

been amplified and is available as a push-pull signal at the collectors of Q834 and Q844.

In the EXT HORIZ position of the HORIZ DISPLAY switch, the external horizontal deflection signal is connected to the base of Q844 through Q824 and the sawtooth signal at the base of Q814 is disconnected. Now, the circuit operates much the same as just described with the sawtooth input. A positive-going external horizontal deflection signal produces a negative-going change at the base of Q844 which

decreases the current flow through this transistor. The col-

lector of Q844 goes positive while the emitter-coupled signal

to Q834 produces a negative-going change at the collector of Q834.

This stage also provides adjustment to set the normal and

magnified gain of the Horizontal Amplifier circuit, and the

MAG switch to provide a horizontal sweep which is mag-

nified 10 times. For normal sweep operation [MAG switch

set to OFF), R835 and R836 cantrol the emitter degeneration

between Q834 and Q844 to set the gain of the stage. R835, Normal Gain, is adjusted to provide calibrated sweep rates.

When the MAG switch, SW801B, is set to the X10 position,

R845 and R846 are connected in parallel with R835 and R836. This additional resistance decreases the emitter degen-

eration of this stage and increases the gain of the circuit

10 times. R845, Mag Gain, is adjusted to provide calibrated magnified sweep rates. When the MAG switch is set to

X10, the MAG ON light, B849, is connected to the +150volt supply through R849. B849 ignites to indicate that the sweep is magnified. In the EXT HORIZ position of the HORIZ

DISPLAY switch, the magnifier is connected into the circuit so the horizontal gain is correct far external horizontal

operation regardless of the setting of the MAG switch. However, both sides of B1049 are connected to ground so it does not ignite.

Output Amplifier

The push-pull output of the Paraphase Amplifier is connected to the Output Amplifier. Each half of the Output Amplifier can be considered as a single-ended, feedback amplifier which amplifies the signal current at the input to

produce a voltage output to drive the horizontal deflection plates of the CRT. The amplifiers have a low input imped-

ance and require very little voltage change at the input to

produce the desired output change. Diodes D851-D852 and D861-D871 protect the amplifier from being overdriven by excessive current swing at the collectors of Q834 and Q844.

Negative feedback is provided from the collectors of the final transistors, Q884 and Q894, to the bases of the input

transistors through C882-R882 and C892-R892. C882 and C892 adjust the transient response of the amplifier so it has good linearity at fast sweep rates.

The Mag Register adjustment, R855, balances the quiescent DC current to the base of Q863 and Q873 so a center-screen display does not change position when the MAG switch is changed from X10 to OFF.

The TRACE FINDER switch, SW330, reduces horizontal

scan by limiting the current available to Q884 and Q894.

Normally the collectors of these transistors are returned to +150 volts. However, when the TRACE FINDER switch is

pressed in, the power from the unregulated +150-volt supply is interrupted and the collector voltage for Q884 and Q894 is supplied from +75 volts through D884. Since the collectors are returned to a lower potential, the output voltage swing is reduced to limit the horizontal deflection within the graticule area.

Z AXIS AMPLIFIER

General

The Z Axis Amplifier circuit controls the CRT intensity

level from several inputs. The effect of these input signals is to either increase or decrease the trace intensity, or to completely blank portions of the display. Fig. 3-15 shows a detailed block diagram of the Z Axis Amplifier circuit. A schematic of this circuit is shown on diagram 16 at the

rear of this manual.

Input Amplifier

The input transistor, Q1014, in the Input Amplifier stage is a current-driven, low-input impedance amplifier. It provides termination for the input signals as well as isola-

tion between the input signals and the following stages. The current signals from the various central sources are connected to the emitter of Q1014 and the sum or difference of the signals determines the collector conduction level. D1015 and D1016 in the collector provide limiting protection at minimum intensity. When the INTENSITY control is set fully counterclockwise (minimum), the collector current of Q1014 is reduced and its collector rises positive. D1015 is reverse biased to block the control current at the base of Q1023, and Q1016 is forward biased to protect the circuit by clamping the collector af Q1014 about 0.5 volts more positive than the emitter level of Q1023. This limiting action also takes place when a blanking signal is applied. The clamping of D1016 allows Q1014 to recover faster to produce a sharper display with sudden changes in blanking level. At normal intensity levels, D1016 is reverse biased and the signal from Q1014 is coupled to emitter

follower Q1023 through D1015.

The input signals vary the current drive to the emitter of

Q1014, which produces a collector level that determines the brilliance of the display. The INTENSITY control sets the

quiescent level at the emitter of Q1014. When R1005 is

turned in the clockwise direction, more current from the INTENSITY control is added to the emitter circuit of Q1014

which results in an increase in collector current to provide a brighter trace. However, the vertical chopped blanking, Z Axis Input and A and B unblanking signals determine whether the trace is visible. The vertical chopped blanking signal blanks the trace during dual-trace switching. This signal

3-22

TM 11-6625-1722-15

Fig. 3-15. Z

Axis Amplifier detailed block diagram.

decreases the current through Q101 4 during the trace switch-

ing time to blank the CRT display. The external blanking input allows an external signal connected to the Z AXIS

INPUT connector to change the trace intensity. A positivegoing signal connected to the Z AXIS INPUT connector decreases trace intensity and a negative-going signal increases trace intensity. The A and B unblanking gate signals from the A and B Sweep Generator circuits blank the CRT during sweep retrace and recovery time so there is no display on the screen. When the Sweep Generator circuits are reset and recovered, (see A and B Sweep Generator discussion for more information) the next trigger initiates the sweep and an unblanking gate signal is generated in the A ar B Sweep Generator circuit that goes negative to allow the emitter current to reach the level established by the INTENSITY control and the other blanking inputs.

Output Amplifier

The resultant signal produced from the various inputs by the Input Amplifier stage is connected to the base of Q1024 through C1029 and to the base of Q1034 through R1024. These transistors are connected as a collector-coupled complementary amplifier. This configuration provides a linear, fast output signal with minimum quiescent power.

The Z Axis Amplifier circuit is a shunt-feedback operational

amplifier with feedback from the Output Amplifier stage to the Input Amplifier stage through C1036-C1037-R1036. The output voltage is determined by the input current times the feedback resistor and is shown by the formula;

is R1036. The unblanking input current change

is approximately two milliamperes. Therefore, the output

adjusts the feedback circuit for optimum high-frequency response.

Zener diode D1043 connected between +75 volts and +150 volts through D1044, R1044 and R1043 produces a +90-volt level at the cathode of D1043. This voltage establishes the correct operating level for the Geometry adjust-

ment in the CRT Circuit ond establishes the correct collector level for Q1043. D1045 connected from base to emitter of Q1043 improves the response of Q1043 to negative-going signals. When the base of Q1043 is driven negative to cutoff, D1045 is forward biased and conducts the negative-going portion of the unblanking signal. This provides a fast falling edge on the unblanking gate to quickly turn the display off. The output unblanking gate at the emitter of Q1043 is connected to the CRT circuit through R1046.

CRT CIRCUIT

General

The CRT Circuit provides the high voltoge and control

circuits necessory for operation of the cathode-ray tube (CRT). Fig. 3-16 shows a detailed block diagram of the CRT Circuit. A schematic, of this circuit is shown on diagram 16 at the rear of this manual.

High-Voltage Oscillator

Q930 and associated circuitry comprise a class C oscilla-

to produce the drive for the high-voltage transformer,

tor T930. When the instrument is turned on, the current through R925 charges C913 positive and Q930 is forward biased.

‘“Lloyd P. Hunter, pp. 14-1 9—1 4-21.

3-23

TM 11-6625-1722-15

Fig. 3-16.

CRT Circuit detailed block diagram.

The collector current of Q930 increoses and a voltage is developed across the collector winding of T930. This produces a corresponding voltage increase in the feedback winding of T930 which is connected to the base of Q930, and it conducts even harder. While Q930 is on, its base current exceeds the current through R925 and C913 charges negatively. Eventually the rate of collector current increase in Q930 becomes less than that required to maintain the voltage across the collector winding and the output voltage drops. This turns off Q930 by way of the feedback voltage to the base. The voltage waveform at the collector of Q930

is a sine wave at the resonant frequency of T930. Q930 remains off until a little less than one cycle later when C913 discharges sufficiently to raise the voltage at the base of Q930 positive enough to bias Q930 into conduction again. The cycle repeats at a frequency of 40 to 50 kilohertz. The amplitude of sustained oscillation depends upon the average current delivered to the base of Q930.

Fuse F937 protects the +12-volt Supply if the High-Voltage Oscillator stage is shorted. C937 and L937 prevent the current changes at the collector of Q930 from affecting the +12-volt regulator circuit.

High-Voltage Regulator

Feedback from the secondary of T930 is connected to the base of Q914 through the voltage divider network R901R910. This sample of the output voltage is compared to the -12-volt level at the emitter of Q914. It is then amplified by Q914 and Q913 and applied to the base of Q923. Amplitude of the oscillations at the collector of Q930

is determined by the average DC level at the emitter of Q923.

Regulation takes place as follows: If the output voltage at the -1950V test point starts to go positive (less negative), a sample of this positive-going voltage is applied to the base of Q914. Q914 is forward biased and it, in turn, forward biases Q913 to increase the conduction of Q923. An increase in current through Q923 raises the average voltage level of its emitter which is connected to the base of Q930 through the feedback winding of T930. A more positive level at the base of Q930 increases the collector current to produce a larger induced voltage in the secondary of T930.

This increased voltage appears as a more negative voltage at the -1950V test point to correct the original positive-

going change. By sampling the output from the cathode

supply in this manner, the total output of the high-voltage

supply is held constant.

Output voltage level of the high-voltage supply is controlled by the High Voltage adjustment, R900, in the base circuit of Q914. This adjustment sets the conduction level

of Q914 which controls the quiescent conduction of Q913, Q923 and Q930 similar to the manner just described for a

change in output voltage.

High Voltage Rectifiers and Output

The high-voltage transformer, T930, has five output windings. Two of these windings provide filament voltage for the rectifier tubes V952 and V962. A third low-voltage wind-

ing provides filament voltage for the cathode-ray tube. The

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TM 11-6625-1722-15

filament voltage can be supplied from the high-voltage

supply since the cathode-ray tube has a very low filament

current drain. Two high-voltage windings provide the nega-

tive and positive accelerating voltage and the CRT grid bias voltage. All of these outputs are regulated by the HighVoltage Regulator stage in the primary of T930 to hold the output voltage constant.

Positive accelerating potential is supplied by voltage doubler V952 and V962. Regulated voltage output is about +8 kilovolts. Ground return for this supply is through the resis-

tive helix inside the cathode-ray tube to pin 7 and then to ground through R972.

The negative accelerating potential for the CRT cathode

is supplied by the half-wave rectifier D952. Voltage output

is about -1.95 kilovolts. A sample of this output voltage is connected to the High-Voltage Regulator stage to provide a regulated high-voltage output.

The half-wave rectifier D940 provides a negative voltage for the control grid of the CRT. Output level is adjustable by R940, CRT Grid Bias adjustment. The neon bulbs B973, B974 and B975 provide protection if the voltage difference between the control grid and cathode exceeds about 165 volts. The unblanking gate from the Z Axis Amplifier is applied to the positive side of this circuit to produce a change in output voltage to control CRT intensity, unblanking, dual-trace blanking and intensity modulation.

CRT Control Circuits

Focus of the CRT display is controlled by the FOCUS control, R967. Divider R963-R968 is connected between the CRT cathode supply and ground. The voltage applied to the

focus grid is more positive (closer to ground level) than the voltage on either the control grid or the CRT cathode. The ASTIG adjustment, R985, which is used in conjunction with

the FOCUS control to provide a well-defined display, varies

the positive level on the astigmatism grid. The +90-volt source for this control is provided by zener diode D1043 in the Z Axis Amplifier circuit.

Geometry adjustment, R982, varies the positive level on the horizontal deflection plate shields to control the overall

geometry of the display. Two adjustments control the trace alignment by varying the magnetic fields around the CRT. The Y Axis Align adjustment, R989, controls the current

through L989 which affects the CRT beam after vertical deflection but before horizontal deflection. The TRACE ROTATION adjustment, R980, controls the current through L980

and affects both vertical and horizontal rotation of the beam.

This configuration operates as a crossover network to provide nearly constant intensity modulation from DC to 50 megahertz.

LOW-VOLTAGE POWER SUPPLY

General

The low-voltage Power Supply circuit provides the operat-

ing power for this instrument from three regulated supplies

and one unregulated supply. Electronic regulation

is used to provide stable, low-ripple output voltages. Each regulated supply contains a short-protection circuit to prevent instru-

ment damage if a supply is inadvertently shorted to ground. The Power Input stage includes the Line Voltage Selector assembly. This assembly allows selection of the nominal operating voltage and regulating rcrnge for the instrument.

Fig. 3-17 shows a detailed block diagram of the Power Supply circuit. A schematic of this circuit is shown on diagram 17 at the rear of this manual.

Power Input

Power is applied to the primary of transformer T1101 through the 115-volt line fuse F1101, POWER switch SW1101, thermal cutout TK1101, Voltage Selector switch SW1102 and Range Selector switch SW1103. The Voltage Selector switch SW1102 connects the split primaries of T1101 in parallel for

115-volt nominal operation, or in series for 230-volt nominal

operation. A second line fuse, F1102, is connected into the circuit when the Voltage Selector switch is set to the 230 V position to provide the correct protection for 230-volt operation (F1102 current rating is one-half of F1101). The fan is connected across one half of the split primary winding so it

always has about 115 volts applied to it.

The Range Selector switch, SW1103, allows the instrument

to regulate correctly on higher or lower than normal line

voltages. Each half of the primary has taps above and

below the 115-volt (230) nominal point. As the Range Selector switch, SW1103, is switched from LO to M to Hl, more

turns are effectively added to the primary winding and the turns ratio is decreased. This provides a fairly constant voltage in the secondary of T1101 even through the primary voltage has increased.

Thermal cutout TK1101 provides thermal protection for this instrument. If the internal temperature of the instrument exceeds a safe operating level, TK1101 opens to interrupt the applied power. When the temperature returns to a safe

level, TK1101 automatically closes to reapply the power.

External Z Axis Input

A signal applied to the Z AXIS INPUT connector (see Z

Axis Amplifier schematic) is applied to the CRT cathode

through C979-C976-R976. DC and low frequency Z-axis sig-

nals are blocked from the CRT circuit by C979. They are connected to the Z Axis Amplifier circuit to produce an increase or decrease in intensity, depending upon polarity. C976 and C979 couple high-frequency signals directly to the CRT cathode to produce the same resultant display as the Z Axis Amplifier circuit produces for low-frequency signals.

-12-volt Supply

The -12-Volt Supply provides the reference voltage for the remaining supplies. The output from the secondary of T1101 is rectified by bridge rectifier D112A-D. This voltage is filtered by C1112 and then applied to the -12-Volt Series Regulator stage to provide a stable output voltage. The Series Regulator can be compared to a variable resistance which is changed to control the output current. The current through the Series Regulator stage is controlled by the Error Amplifier to provide the correct regulated output voltage.

“~utler, pp.

559-625.

3-25

TM 11-6625-1722-15

3-26

Fig. 3-17.

Power Supply

detailed block diagram.

TM 11-6625-1722-15

The Error Amplifier is connected as a comparator. Reference voltage for the comparator is provided by zener diode D1114 which sets the base of Q1114 at about –9 volts. The base level of Q1124 is determined by voltage divider R1121R1122-R1123 between the output of this supply and ground. R1122 is adjustable to set the output voltage of this supply

to -12 volts. R1119 is the emitter resistor for both com-

parator transistors and the current through it divides be-

tween Q1114 and Q1124. The output current of the Error Amplifier stage controls the conduction of the Series Regulator stage (through Q1133). This output current changes to

provide a canstant, low-ripple –12-volt output level. This

occurs as follows: The -12-volt regulatar maintains equal voltage at the bases of the Error Amplifier transistors Q1114 and Q1124. If the -12 Volts adjustment R1122, is turned clockwise, the current through Q1124 increases (Q1124 base tends to go more positive than the base of Q1114) and the current through Q1114 decreases. Decreased current through Q1114 produces less voltage drop across R1117 and the base of Q1133 goes positive. The emitter of Q1133 pulls the base of Q1137 positive to increase the current through the load, thereby increasing the output voltage of the supply. This places more voltage across divider R1121-R1122-R1123 and the divider action returns the base of Q1124 to about -9 volts. A similar, but opposite, action takes place when R1122 is turned counterclockwise so the base of Q1124 is more negative than the base of Q1114. The -12 Volts adjustment R1122, is set to provide a -12-volt level at the output of this supply.

The output voltage is regulated to provide a constant voltage to the load by feeding a sample of the output back to the Series Regulator, Q1137. For example, assume that the output voltage increases (more negative) because of a change in load or an increase in line voltage. This negative-going level at the output is applied across the voltage divider R1121-R1122-R1123 and the base of Q1124 goes negative

also. This reduces the current flow through Q1124 which allows Q1114 to conduct more and its collector goes negative. When the collector of Q1114 goes negative, the bias on Q1133 is reduced, resulting in reduced current through

the Series Regulator, Q1137. Reduced current through Q1137

also means that there is less current through the load and the output voltage decreases (less negative). In a similar

manner the Series Regulator and Error Amplifier stages compensate for output changes due to ripple.

The Short-Protection Amplifier stage, Q1129, protects the

-12-Volt Supply if the output is shorted. For normal opera-

tion, the emitter-base voltage of Q1129 is not enough to bias it on. However, when the output is shorted, high current is demanded from the -12-Volt Supply, and this current flows through R1129. The voltage drop across R1129 becomes

sufficient to forward bias Q1129 and its collector current

produces an increased voltage drop across R1117. The increased voltage drop across R1117 reduces the current flow

of both Q1133 and Q1137 to limit the output current.

R1151-R1152-R1153 between the regulated -12 volts and the output of this supply. The -12 volts is held stable by the –12-Volt Supply as discussed previously. If the +12-volt output changes, a sample of this change appears at the base of Q1154 as an error signal. Regulation of the output voltage is controlled by the +12-Volt Series Regulator stage,

Q1167, in a similar manner to that described for the –12Volt Supply. The +12 Volts adjustment, R1152, sets the output level to +12 volts. D1152 provides thermal compensation for the Error Amplifier. C1164 improves response of the regulator circuit to AC changes at the output.

Shorting protection is provided by Q1159 and R1159. If the output of this supply is shorted, Q1159 is biased on to limit the conduction of the Series Regulator in the same manner as described for the -12-Volt Short-Protection Amplifier. D1164 protects Q1154 when the output of this supply is

shorted.

+75-Volt Supply

D1172 A-D provides the rectified voltage for the +75-

Volt Supply. C1172 filters the rectified voltage which is connected to the +75-Volt Series Regulator. Reference voltage for this supply is provided by voltage-divider R1181-R1182R1183 between the regulated -12 volts and the output of this supply. Since the -12 volts is held stable by the -12Volt Regulator circuit, any change at the base of Error Amplifier Q1184 is due to change at the output of the +75Volt Supply. Regulation of the output voltage is controlled by Error Amplifier Q1184-Q1193 and Series Regulator,

Q1197, in a manner similar to that described for the +12Volt Supply. The +75 Volts adjustment R1182, sets the quiescent conduction level of the Error Amplifier stage to provide an output level of +75 volts. The output of the +150Volt Supply (unregulated) is connected to the Error Amplifier to provide the required collector supply for stable opera-

tion. Zener diode D1209 establishes a volage at its cathode of about +108 volts. Then, R1186, zener diode D1185 and

R1185 drop this voltage to the correct level for the operation of Q1184. D1182 provides thermal compensation for the

Error Amplifier.

Q1189 provides current limiting for this supply through

D1188. Quiescently, Q1189 is off and under normal operating conditions, D1189 is conducting and D1188 is reverse biased. However, when the output is shorted, the increased current flow thraugh R1187 biases Q1189 on and its collector goes negative. This forward biases D1188 and reverse biases D1189. Now Q1189 limits the collector current of Q1197 through Q1193. F1172 also provides overload protection. D1198 protects the +75-volt supply from damage if it is shorted to the -12-volt output.

+150-Volt Unregulated Supply

+12-Volt Supply

Rectified voltage for operation of the +12-Volt Supply is provided by D1142 A-D. This voltage is filtered by C1142 and connected to the +12-Volt Supply Series Regulator and to the High-Voltage Oscillator stage in the CRT Circuit. Reference voltage for this supply is provided by voltage divider

Rectifiers D1202 and D1212 provide the unregulated output for the +150-Volt Supply. The output of the +75-Volt Supply is connected to the negative side of the +150-Volt Supply to elevate the output level to +150 volts. Diodes D1202 and D1212 are connected as a full-wave center-tapped rectifier and the output is filtered by C1202-C1204-R1204 to hold the output level at about +150 volts. Fuse F1204 protects this supply if the output is shorted.

3-27

TM 11-6625-1722-15

6.3-Volt RMS AC Source

The 6.3-volt RMS secondary winding of T1101 provides power for the POWER ON light, B1107, and the scale illumination lights, B1108 and B1109. The current through the

scale illumination lights is controlled by the SCALE ILLUM control, R1108, to change the illumination of the graticule

line voltage to the A and B Trigger Generatar circuits for line voltage to the A and B Trigger Generaar circuits for internal triggering at the line frequency. C1105 reduces noise on the line frequency signal.

VOLTAGE DISTRIBUTION

Diagram 17 also shows the distribution of the output volt-

ages from the Power Supply circuit to the circuit boards in this instrument. The decoupling networks which provide decoupled operating voltages are shown on this Diagram and are not repeated on the individual circuit diagrams.

CALIBRATOR

General

The Calibrator circuit produces a square-wave output with accurate amplitude and frequency. This output is available as a square-wave voltage at the 1 kHz CAL connector or as a square-wave current through the side-panel PROBE

LOOP. Fig. 3-18 shows a detailed block diagram of the Calibratar circuit. A schematic of this circuit is shown on diagram 18 at the rear of this manual.

Oscillator

Q1255 and its associated circuitry comprise a tuned-col-

lector oscillator.

Frequency of oscillation is determined by the LC circuit comprised of the primary of variable transformer T1255 in parallel with C1255. The accuracy and sta-

“Lloyd P. Hunterr pp. 14-3—1

4.7. square wave.

bility required to provide an accurate time and frequency

reference is obtained by using a capacitor and transformer

which have equal but opposite temperature coefficients.

The oscillations of the LC circuit, T1255-C1255, are sustained by the feedback winding of T1255 connected to the base of Q1255. C1266 connects a sample of the output of the LC circuit to the base of Q1265. The regenerative feedback from the emitter of Q1265 to the emitter of Q1255 produces fast changeover between Q1255 and Q1265 to provide a fast risetime on the output square wave. Frequency of the output square wave can be adjusted by varying the coupling to the feedback winding of T1255. The squarewave signal at the collector of Q1265 is connected to the Output Amplifier.

Output Amplifier

The output signal from the oscillator stage saturates Q1274 to produce the accurate square wave at the output. When the base of Q1274 goes positive, Q1274 is cut off and the output signal drops negative to ground. When its base goes negative, Q1274 is driven into saturation and the output signal rises positive to about +12 volts. The output of the +12-Volt Supply is adjusted for an accurate one-volt output signal at the 1 kHz CAL connector when the Calibrator switch is set to 1 V.

Output Divider

The Output Divider, R1275-R1276-R1277, provides two output voltages from the Calibrator circuit. In the 1 V CALlBRATOR switch position, voltage is obtained from the calIector of Q1274 through R1274. In the .1 V CALIBRATOR switch position, the output is obtained at the junction of voltage divider R1275 and R1276-R1277 to provide one-tenth of the previous output voltage.

Collector current of Q1274 flows through the PROBE LOOP on the side panel. Output current is a five-millampere

3-28

Fig. 3-18.

Calibrator

detailed block diagram.

SECTION 4

MAINTENANCE

TM 11-6625-1722-15

Introduction

This section of the manual contains maintenance information for use in preventive maintenance, corrective maintenance or troubleshooting of the Type 453.

Cover Removal

The top and bottom covers of the instrument are held in place by thumb screws located on each side of the instrument. To remove the covers, loosen the thumb screws and slide the covers off the instrument. The covers protect the instrument from dust in the interior. The covers also direct the flow of cooling air and reduce the EMI radiation from the instrument.

PREVENTIVE MAINTENANCE

General

Preventive maintenance consists of cleaning, visual inspec-

on, lubrication, etc. Preventive maintenance performed on a regulor basis may prevent instrument breakdown and will improve the reliability of this instrument. The severity of the environment to which the Type the frequency of maintenance.

Cleaning

General. The Type 453 should be cleaned as aften os

operating conditions require. Accumulation of dirt in the instrument can cause overheating and component breakdown.

Dirt on components acts as an insulating blanket and prevents efficient heat dissipation. It also provides an electrical conduction path.

CAUTION

Avoid the use of chemical cleaning agents which might damage the plastics used in this instrument. Avoid chemicals which contain benzene, toluene, xylene, acetone or similar solvents.

The top and bottom covers provide protection against dust

n the interior of the instrument. Operation without the covers in place necessitates more frequent cleaning. The front cover provides dust protection for the front panel and the CRT face. The front cover should be installed for storage or transportation. The plastic cover supplied with the Type 453 provides protection for the outside of the instrument during transportation or storage. The pocket on the side also provides a convenient place to carry this instruction manual.

453 is subjected determines

Air Filter. The air filter should be visually checked every few weeks and cleaned or replaced if dirty. More frequent inspections are required under severe operating conditions. The following procedure is suggested for cleaning the filter.

1. Remove the filter by pulling it out of the retaining frame on the rear panel. Be careful not to drop any of the accumulated dirt into the instrument.

2. Flush the loose dirt from the filter with a stream of hot

water.

3. Place the filter in a solution of mild detergent and hot

water and let it soak for several minutes.

Squeeze the filter to wash out any dirt which remains. Rinse the filter in clear water and allow it to dry.

5. Coat the dry filter with an air-filter adhesive,

Let the adhesive dry thoroughly.

7. Re-install the filter in the retaining frame.

Exterior. Loose dust accumulated on the outside of the Type 453 can be removed with a soft cloth or small paint brush. The paint brush is particularly useful for dislodging dirt on and around the front-panel controls. Dirt which remains can be removed with a soft cloth dampened in a mild detergent and water solution. Abrasive cleaners should not be used.

CRT. Clean the plastic light filter, faceplate protector and the CRT face with a soft, lint-free cloth dampened with denatured alcohol. The CRT mesh fiiter can be cieaned in the following manner.

1. Hold the filter in a vertical position and brush lightly with a soft #7 water-color brush to remove light coatings of dust or lint.

2. Greasy residues or dried-on dirt can be removed with a solution of warm water and a neutral-pH liquid detergent. Use the brush to lightly scrub the filter.

3. Rinse the filter thoroughly in clean water and allow to air dry.

4. If any lint or dirt remains, use clean low-pressure air to remove. Do not use tweezers or other hard cleaning tools on the filter, as the special finish may be damaged.

5. When not in use, store the mesh fiiter in a lint-free, dust-proof container such as a plastic bag.

4-1

TM 11-6625-1722-15

Interior. Dust in the interior of the instrument should be removed occasionally due to its electrical conductivity under high-humidity conditions. The best way to clean the interior it to blow off the accumulated dust with dry, low-velocity air. Remove any dirt which remains with a soft paint brush or a cloth dompened with a mild detergent and water solution. A cotton-tipped applicator is useful for cleaning in narrow spaces or for cleaning ceramic terminal strips and circuit boards.

The high-voltage circuits, particularly parts located in the high-voltage compartment and the area surrounding the post-deflection anode connector, should receive special attention. Excessive dirt in these areas may cause highvoltage arcing and result in improper instrument operation.

Lubrication

General. The reliability of potentiometers, rotary switches

and other moving parts can be maintained if they are kept

properly lubricated. Use a cleaning-type lubricant (e.g., Tektronix Part No. 006-0218-00) on switch contacts. Lubricate switch detents with a heavier grease (e.g., Tektronix Part No. 006-0219-00). Potentiometers which are not permanently sealed should be lubricated with a lubricant which does not affect electrical characteristics (e.g., Tektronix Part No. 006-0220-00). The pot lubricant can also be used on shaft bushings. Do not over-lubricate. A lubrication kit containing the necessary lubricants and instructions is available from Tektronix, Inc. Order Tektronix Part No. 003-0342-00.

troubles may be revealed and/or corrected by recalibration.

TROUBLESHOOTING

Introduction

The following information is provided to facilitate troubleshooting of the Type 453. Information contained in other sections of this manual should be used along with the following information to aid in locating the defective component. An understanding of the circuit operation is very help-

ful in locating troubles. See the Circuit Description section

for complete information.

Troubleshooting Aids

Diagrams. Circuit diagrams are given on foldout pages in Section 9. The component number and electrical value of each component in this instrument are shown on the diagrams. Each main circuit is assigned a series of component

numbers. Table 4-1 lists the main circuits in the Type 453 and

the series of component numbers assigned to each. Important voltages and waveforms are also shown on the diagrams. The portions of the circuit mounted on circuit boards are

enclosed with a blue line.

TABLE 4-1

Fan. The fan-motor bearings are sealed and do not re-

quire lubrication.

Visual Inspection

The Type 453 should be inspected ossasionally for such defects as broken connections, broken or damaged ceramic strips, improperly seated transistors, damaged circuit boards

and heat-damaged parts.

The corrective precedure for most visible defects is obvi-

ous; however, particular care must be taken if heat-damaged components are found. Overheating usually indicates other trouble in the instrument; therefore, it is important that the cause of over-heating be corrected to prevent recurrence of the damage.

Transistor Checks

Periodic checks of the transistors in the Type 453 are not recommended. The best check of transistor performance is its actual operation in the instrument. More details on checking transistor operation is given under Troubleshooting.

Recalibration

To assure accurate measurements, check the calibration of this instrument after each 1000 hours of operation or every six months if used infrequently. In addition, replacement of

components may necessitate recalibration of the affected

circuits. Complete calibration instructions are given in the

Calibration section.

The calibration procedure can also be helpful in localiz-

ing cerain troubles in the instrument. In some cases, minor

Switch Wafer Identification. Switch wafers shown on the diagrams are coded to indicate the position of the wafer in the complete switch assembly. The numbered portion of the code refers to the wafer number counting from the front, or mounting end of the switch, toward the rear. The letters F and R indicate whether the front or rear of the wafer performs the particular switching function. For example, a wafer designated 2R indicates that the rear of the second wafer from the front is used for this particular switching function.

Circuit Boards. Fig. 4-6 through 4-14 show the circuit boards used in the Type 453. Fig. 4-5 shows the location of each board within the instrument. Each electrical component on the boards is identified by its circuit number.

4-2

TM 11-6625-1722-15

The circuit boards are also outlined on the diagrams with a blue line. These pictures, used along with the diagrams, aid in locating the components mounted on the circuit boards.

Wiring Color-Code. All insulated wire and cable used in the Type 453 is color-coded to facilitate circuit tracing. Signal carrying leads are identified with one or two colored

stripes. Voltage supply leads are identified with three stripes

to indicate the approximate voltage using the EIA resistor color code. A white background color indicates a positive voltage and a tan background indicates a negative voltage.

The widest color stripe identifies the first color of the code. Table 4-2 gives the wiring color-code for the power-supply

voltages used in the Type 453.

TABLE 4-2

Power Supply Wiring Color Code

Resistor Color-Code. In addition to the brown com-

position resistors, some metal-film resistors and some wirewound resistors are used in the Type 453. The resistance values of wire-wound resistors are printed on the body of the component. The resistance values of composition resistors and metal-film resistors are color-coded on the components with EIA color-code (some metal-film resistors may have the value printed on the body). The color-code is read starting with the stripe nearest the end of the resistor. Composition resistors have four stripes which consist of two signi-

ficant figures, a multiplier and a tolerance value (see Fig. 4-1). Metal-film resistors have five stripes consisting of three significant figures, a multiplier and a tolerance value.

Capacitor Marking. The capacitance values of common disc capacitors and small elecrolytics are marked in microfarads on the side of the component body. The white ceramic capacitors used in the Type 453 are color coded in picofarads using modified EIA code (see Fig. 4-1).

Diode Color Code. The cathode end of each glass-encased diode is indicated by a stripe, a series of stripes or a dot. For most silicon or germanium diodes with a series of stripes, the color-code also indicates the type of diode and identifies the Tektronix Part Number using the resistor colorcode system (e.g., a diode color-coded blue-brown-graygreen indicates diode type 6185 with Tektronix Part Number

Fig. 4-1.

Celor cad. for resistars and ceramic capacitors.

4-3

TM 11-6625-1722-15

Fig. 4-2.

Electrode configuration for semiconductors in this instrument.

152-0185-00). The cathode and anode end of metal-encased

diodes can be identified by the diode symbol marked on the

body.

Transistor Lead Configuration. Fig. 4-2 shows the lead configurations of the transistors used in this instrument. This view is as seen from the bottom of the transistors.

Troubleshooting Equipment

The following equipment is useful for troubleshooting the Type 453.

1. Transistor Tester Description: Tektronix Type 575 Transistor-Curve Tracer

or equivalent.

Purpose: To test the semiconductors used in this instrument.

2. Multimeter Description: VTVM, 10 megohm input impedance and 0 to

500 volts range; ohmmeter, 0 to 50 megohms. Accuracy, within 3%. Test prods must be insulated to prevent accidental shorting.

Purpose: To check voltages and for general troubleshoot-

ing in this instrument.

NOTE

A 20,000 ohms/volt VOM can be used to check the voltages in this instrument if allowances are made for the circuit loading of the VOM at highimpedance points.

3. Test Oscilloscope Description: DC to 20 MHz frequency response. 5 milli-

volts to 10 volts/division deflection factor.

Use a 10X

probe.

Purpose: To check waveforms in this instrument.

Troubleshooting Techniques

This troubleshooting procedure is arranged in an order which checks the simple possibilities before proceeding with extensive troubleshooting. The first few checks assure proper connection, operation and calibration. If the trouble is not

located by these checks, the remaining steps aid in locating

the defective component. When the defective component is

located, it should be replaced following the replacement pro-

cedures given under Corrective Maintenance.

4-4

TM 11-6625-1722-15

1. Check Control Settings. Incorrect control settings can

indicate a trouble that does not exist. If there is any question

the page until a step is found which is not correct. Further

checks and/or the circuit in which the trouble is prabably about the correct functian or operation of any control, see located are listed to the right of this step. the Operating Instructions section of this manual.

2. Check Associated Equipment. Before proceeding with

troubleshooting of the Type 453, check that the equipment

used with this instrument is operating correctly. Check that the signal is properly connected and that the interconnecting cables are not defective. Also, check the power source.

3. Visual Check. Visually check the portion of the instru- ment in which the trouble is located. Many troubles can be located by visual indications such as unsoldered connections, broken wires, damaged circuit boards, damaged components, etc.

4. Check Instrument Calibration. Check the calibration of this instrument, or the affected circuit if the trouble exists in one circuit. The apparent trouble may only be a result of misadjustment or may be corrected by calibration. Complete calibration instructions are given in the Calibration section

After the defective circuit-has been located, proceed with

steps 6 through 8 to locate the defective component(s).

6. Check Circuit Board Interconnections. After the trouble has been isolated to a particular circuit, check the pin connectors on the circuit board for correct connection. Figs. 4-8 through 4-16 show the correct connections for each board.

The pin connectors used in this instrument also provide a convenient means of circuit isolation. Far example, a short in a power supply can be isolated to the power supply itself by disconnecting the pin connectors for that voltage at the

remaining boards.

7. Check Voltage and Waveforms. Often the defective

component can be located by checking for the correct volt-

age or waveform in the circuit. Typical voltages and waveforms are given on the diagrams.

of this manual.

NOTE

5. Isolate Trouble to a Circuit. To isolate trouble to a circuit, note the trouble symptom. The sympton often identifies the circuit in which the trouble is located. For example, poor focus indicates that the CRT (includes high voltage) circuit is probably at fault. When trouble symptoms appear in more than one circuit, check affected circuits by taking voltage and waveform readings. Also check for the correct output signals at the side-panel output connectors with a test oscilloscope. If the signal is correct, the circuit is working correctly up to that point. For example, correct amplitude and time of the A Gate out waveform indicates that the A Trigger Generatar and A Sweep Gate circuits are operating correctly.

Incorrect operation of all circuits often indicates trouble in the power supply. Check first for correct voltage of the individual supplies. However, a defective component elsewhere in the instrument can appear as a power-supply trouble

and may also affect the operation of other circuits. Table 4-3 lists the tolerances of the power supplies in this instru-

ment. [f a power-supply voltage is within the listed tolerance, the supply can be assumed to be working correctly. If outside the tolerance, the supply may be misadjusted or operating incorrectly. Use the procedure given in the Calibration section to adjust the power supplies.

TABLE 4-3

Power Supply Tolerance

Voltages and wavefarms given on the diagrams

are not absolute and may vary slightly between

instruments. To obtain operating conditions similar

to those used to take these readings, see the first diagram page.

8. Check Individual Components. The following procedures describe methods of checking individual components in the Type 453. Components which are soldered in place

are best checked by disconnecting one end. This isolates the

measurement from the effects of surrounding circuitry.

A. TRANSISTORS. The best check of transistor operation is actual performance under aperating conditions. transistor is suspected of being defective, it can best be checked by substituting a new component or one which has been checked previously. However, be sure that circuit

conditions are not such that a replacement transistor might also be damaged. If substitute transistors are not available,

use a dynamic tester (such as Tektronix Type 575). Statictype testers are not recommended, since they do not check

operation under simulated operating conditions.

B. DIODES. A diode can be checked for an open or

shorted condition by measuring the resistance between

terminals.

With an ohmmeter scale having an internal source of between 800 millivolts and 3 volts, the resistance should be very high in one direction and very low when the

leads are reversed.

If a

lAd@ed tion procedure.

for

eorreet

output from

the

Calibrator

circuit; see

Calibra-

Fig. 4-3 provides a guide to aid in locating a defective circuit. This chart may not include checks for all possible defects; use steps 6-8 in such cases. Start from the top of the chart and perform the given checks on the left side of

CAUTION

Do not use an ohmmeter scale that has a high internal current. High currents may damage the diode. Do not measure tunnel diodes with an ohmmeter; use a dynamic tester (such as a Tektronix

Type 575 Transistor-Curve Tracer).

C. RESISTORS. Check the resistors with an ohmmeter. Check the Electrical Parts List for the tolerance of the resistors used in this instrument. Resistors normally do not need to be replaced unless the measured value varies widely from the specified value.

4-5

4-6

TM 11-6625-1722-15

4-7

Fig. 4-3.

TM 11-6625-1722-15

D. INDUCTORS. Check for

continuity with an ohmmeter.

open inductors by checking

Shorted or partially shorted inductors can usually be found by checking the waveform response when high-frequency signals are passed through the circuit. Partial shorting often reduces high-frequency response (roll-off).

E. CAPACITORS. A leaky or shorted capacitor can best be detected by checking resistance with an ohmmeter on the highest scale. Do not exceed the voltage rating of the capacitor. The resistance reading should be high after initial charge of the capacitor. An open capacitor can best

be detected with a capacitance meter or by checking whether the capacitor passes AC signals.

9. Repair and Readjust the Circuit. If any defective

parts are Iocated, follow the replacement procedures given

in this section. Be sure to check the performance of any cir-

cuit that has been repaired or that has had any electrical components replaced.

CORRECTIVE MAINTENANCE

General

Corrective maintenance consists of component replacement

and instrument repair. Special techniques required to replace

components in this instrument are given here.

Soldering Techniques

WARNING

Disconnect the instrument from the power source

before soldering.

Circuit Boards. Use ordinary 60/40 solder and a 35- to 40-watt pencil type soldering iron on the circuit boards. The tip of the iron should be clean and properly tinned for best heat transfer to the solder joint. A higher wattage soldering iron may separate the wiring from the base material.

The following technique should be used to replace a component on a circuit board. Most components can be replaced without removing the boards from the instrument.

1. Grip the component lead with long-nose pliers. Touch the soldering iron to the lead at the solder connection. Do not lay the iron directly on the board.

2. When the solder begins to melt, pull the lead out gently. This should leave a clean hole in the board. If not, the hole can be cleaned by reheating the solder and placing a sharp object such as a toothpick into the hole to clean it out. A vacuum-type resoldering tool can also be used for

this purpose.

3. Bend the leads of the new component to fit the holes in the board. If the component is replaced while the board is mounted in the instrument, cut the leads so they will just

protrude through the board. Insert the leads into the holes in the board so the component is firmly seated against the board (or as positioned originally). If it does not seat properly, heat the solder and gently press the component into

place.

4. Touch the iron to the connection and apply a small amount of solder to make a firm solder joint; do not apply too much solder. To protect heat-sensitive components, hold the lead between the component body and the solder joint with a pair of long nose pliers or other heat sink.

5. Clip the excess lead that protrudes through the board.

6. Clean the area around the solder connection with a flux-remover solvent. Be careful not to remove information printed on the board.

4-8

Ceramic Terminal Strips.

Solder used on the ceramic terminal strips should contain about 3% silver. Use a 40to 75-watt soldering iron with a tip. Ordinary solder should not be used

the ceramic terminal strips.

If ordinary solder is used repeatedly or if excessive heat is applied, the solder-to-ceramic bond may be broken.

A sample roll of solder containing about 3% silver is mounted on the rear subpanel of this instrument. Additional solder of the same type should be available locally, or it

can be procured under FSN 3439-912-8698.

Observe the following precautions when soldering to

ceramic terminal strips.

1. Use a hot iron for a shorT time. Apply only enough

heat to make the solder flow freely.

2. Maintain a clean, properly tinned tip.

3. Avoid putting pressure on the ceramic terminal strip.

4. Do not attempt to fill the terminal-strip notch with

solder; use only enough solder to cover the wires adequately.

5. Clean the flux from the terminal strip with a flux-

remover solvent.

Metal Terminals. When soldering metal terminals (e.g., switch terminals, potentiometers, etc), ordinary 60/40 solder can be used. Use a soldering iron with a 40- to 75-watt

Observe the following precautions when soldering metal terminals:

1. Apply only enough heat to make the solder flow

freely.

2. Apply only enough solder to form a solid connection.

Excess solder may impair the function of the part.

3. If a wire extends beyond the solder joint, clip off the

excess.

4. Clean the

flux from the solder joint with a flux-remover

solvent.

Component

Replacement

WARNING

Disconnect the instrument from the power source before replacing components.

Removing the Rear Panel. The rear panel must be removed for access to the rear subpanel. This panel can be removed by removing the Z Axis ground strap and the four screws located near the rear feet.

Swing-Out Chassis.

Some of the controls and connectors are mounted on a swing-out chassis on the right side of this instrument. To reach the rear of this chassis or the components mounted behind it, first remove the top cover from the instrument. Then, loosen the captive securing screw so the chassis can swing outward.

Ceramic Terminal Strip Replacement. A complete ceramic terminal strip assembly is shown in Fig. 4-4. Replacement strips (including studs) and spacers are supplied under separate part numbers. However, the old spacers may be re-used if they are not damaged. The applicable Tektronix

Part Numbers for the ceramic strips and spacers used in

this instrument are given in the Mechanical Parts List.

To replace a ceramic terminal strip, use the following

pracedure: REMOVAL:

1. Unsolder all components and connections on the strip.

To aid ih replacing the strip, it may be advisable to mark

TM 11-6625-1722-15

Fig. 4-4. Troubleshooting

chart for

Type

453.

each lead or draw a sketch to show location of the com-

ponents and connections.

2. Pry or pull the damaged strip from the chassis. Be

careful not to damage the chassis.

3. If the spacers come out with the strip, remove them from the stud pins for use on the new strip (spacers should be replaced if they are damaged).

REPLACEMENT:

1. Place the spacers in the chassis holes.

2. Carefully press the studs of the strip into the spacers until they are completely seated. If necessary, use a soft mallet and tap lightly, directly over the stud, to seat the strip completely.

3. If the stud extends through the spacers, cut off the

excess.

4. Replace all components and connections. Observe the soldering precautions given under Soldering Techniques in this section.

Circuit Board Replacement. If a circuit board is damaged beyond repair, either the entire assembly including all soldered-on components, or the board only, can be replaced. Part numbers are given in the Mechanical Parts List for either the completely wired or the unwired board. Most of the components mounted or, the circuit boards can be replaced without removing the boards from the instrument. Observe the soldering precautions given under Soldering Techniques in this section. However, if the bottom side of the board must be reached or if the board must be moved to gain access to other areas of the instrument, only the mounting screws need to be removed. The interconnecting wires on most of the boards are long enough to allow the board to be moved out of the way or turned over without disconnecting the pin connectors.

GENERAL:

Most of the connections to the circuit boards are made with pin connectors.

However, several connections are soldered between the attenuators and Vertical Preamp board. See the special removal instructions to remove these as a

unit.

Use the following procedure to remove a circuit board.

4-9

TM 11-6625-1722-15

1. Disconnect all pin connectors

which come through holes

in the board.

2. Remove aII screws holding the board to the chassis.

3. The board may now be lifted for maintenance or access

to areas beneath the board.

4. To completely remove the board, disconnect the remain-

ing pin connectors.

5. Lift the circuit board out of the instrument. Do not

force or bend the board.

6. To replace the board, reverse the order of removal. Correct location of the pin connectors is shown in Fig. 4-8 through 4-16. Replace the pin connectors (carefully so they mate correctly with the pins. If forced into place incorrectly

positioned, the pin connectors may be damaged.

VERTICAL PREAMP UNIT REMOVAL:

Use the following procedure to remove the Vertical Pre-

amp board and the attenuators as a unit.

1. Remove the screw (mounted with a washer) which holds the MODE-TRIGGER switch (rear of board) to the chassis. The other screw may be left in place.

2. Remove the screw (with fiber washer) from the center

of the board.

3. Unsolder the connections on he MODE TRIGGER switch

which do not go to the Vertical Prearnp board.

4. Disconnect all pin connectors which lead off of the

Vertical Preamp board.

5. Remove the attenuator shield and remove the nuts (four) located under this shield at each side of the INPUT connectors.

6. Remove the VARIABLE, CH 1 and CH 2 VOLTS/DIV,

POSITION, Input Coupling, TRIGGER and MODE knobs.

7. Remove the securing nuts on the VOLTS/DIV switches

and the STEP ATTEN BAL controls.

8. Remove the three screws at the rear of the board.

9. Lift up on the rear of the assembly and slide it out

of the instrument.

10. The board may now be removed from the Vertical Preamp unit as follows:

a. Disconnect all pin connectors remaining on the

board.

b. Unsolder all connections on the rear side of the board which connect between the attenuators and the board. Observe the soldering precautions given in this section.

c. Remove the remaining screw whichi holds the MODE-

TRIGGER switch to the board.

d. Remove the four screws holding the board to the

attenuators.

11. To replace the unit,

reverse the order of removal.

Be sure the GAIN and INVERT extensions are positioned

correctly in the corresponding front-panel holes.

be worn. Avoid striking it on any object which might cause it to crock or implode. When storing a CRT, place it face down

On a smooth surface with a protective cover or soft

mat under the faceplate to protect it from scratches.

The CRT shield should also be handled carefully. This shield protects the CRT display from distortion due to magnetic interference. If the shield is dropped or struck sharply, it may lose its shielding ability.

The following procedure outlines the removal and replace-

rnent of the cathode-ray tube: A. REMOVAL:

1. Remove the top and bottom covers and rear panel as

described previously.

Remove the light filter or faceplate protector.

2. Disconnect the CRT anode connector. Ground this lead

3. the anode conection to discharge any stored charge.

and

Unsolder the trace-rotation leads at the CRT shield.

Unsolder the y-axis rotation leads at the Y Axis Align

control.

6. Disconnect the deflection-plate connectors. Be careful

not to bend the deflection-plate pins.

7. Remove the CRT socket.

8. Remove the two nuts (by the graticule iights) which

hold the front of the CRT shield to the subpanel.

9. Remove the graticule lights from the studs and position

them away from the shield.

10. Loosen the two hex-head screws inside the rear of the CRT shield. Remove the shield angle clamps and mounting screws.

11. Slide the CRT assembly to the rear of the instrument until the faceplate clears the mounting studs. Then, lift the front of the CRT assembly up and slide it out of the instrument.

12. Loosen the three screws on the CRT clamp inside the CRT shield. Do not remove the screws.

13. Hold the left hand on the CRT faceplate and push forward on the CRT base with the right hand. As the CRT starts out of the shield, grasp it firmly with the left hand. When the CRT is free of the clamp, slide the shield completely off the CRT. Be careful not to bend the neck pins.

B. REPLACEMENT:

1. Insert the CRT into the shield. Be careful not to bend

the neck pins. Seat the CRT firmly against the shield.

2. Tighten the bottom clamp screw-inside the CRT shield. Recommended tightening torque: 4 to 7 inch-lbs. Do not tighten the screws on the sides.

3. Place the light mask over the CRT faceplate.

4. Using a method similar to that for removal (step 11) re-insert the CRT assembly into the instrument. Be sure the

faceplate seats properly in the subpanel.

CRT

Cathode-Ray Tube Replacement. Use care when han-

dling a CRT. Protective clothing and safety glasses should

4-10

Tighten the two remaining screws on the inside of the

5. CRT

shield.

TM 11-6625-1722-15

Replace the shield angle clamps and mounting screws on the rear subpanel. Tighten the two hex-head screws inside the rear of the CRT shield.

7. Replace the graticule lights and securing nuts.

Replace the CRT socket.

Reconnect the anode connector. Align the jack on the CRT and then plug in the connector and press firmly on the insulated cover to snap the plug into place.

10. Reconnect the trace-rotation and y-axis leads.

11. Reconnect the deflection-plate connectors. Correct

location is indicated on the CRT shield.

12. Adiust the High Voltage, TRACE ROTATION, ASTIG, Y-Axis Align and Geometry adjustment. Adjustment procedure is given in the Calibration sectian. Also check the basic vertical and horizontal gain.

Transistor Replacement. Transistors should not be replaced unless actually defective. If removed from their sockets during routine maintenance, return them to their original sockets. Unnecessary replacement of transistors may affect the calibration of this instrument. When transistors are replaced, check the operation of that part of the instrument which may be affected.

CAUTION

POWER switch must be turned off before removing

or replacing transistors.

Replacement transistors should be of the original type or a direct replacement. Fig. 4-2 shows the lead configuration of the transistors used in this instrument. Some plastic case transistors have lead configurations which do not agree with those shown here. If a transistor is replaced by a transistor which is made by a different manufacturer than the original, check the manufacturer’s basing diagram for correct basing. wired for the basing used for metal-case transistors. Transistors which have heat radiators or are mounted on the chassis use silicone grease to increase heat transfer. Replace the silicone grease when replacing these transistors.

Handle silicone grease with care. Avoid getting silicone grease in the mouth or eyes. Wash hands thoroughly after use.

Two transistors in both the Channel 1 and Channel 2 Preamp circuit (Vertical Preamp circuit board) are permanently mounted in special temperature compensation blocks. These transistors (along with the temperature compensation block) must be replaced as a unit. When replacing the unit, place it so the reference information faces the left side of the instrument and the PNP transistor (labeled on side of unit) is toward the front of the instrument.

Fuse Replacement. Table 4-4 gives the rating, location,

and function of the fuses used in this instrument.

Rotary Switches. Individual wafers or mechanical parts of rotary switches are normally not replaceable. If a switch is defective, replace the entire assembly. Replacement switch-

All transistor sockets in this instrument are

WARNING

es can be ordered either wired or unwired; refer to the Parts List for the applicable part numbers.

When replacing a switch, tag the leads and switch termi-

nals with corresponding identification tags as the leads are disconnected. Then, use the old switch as a guide for installing the new one. An alternative method is to draw a

sketch of the switch layout and record the wire color at each terminal. When soldering to the new switch be careful that

TABLE 4-4

the solder does not flow beyond the rivets on the switch terminals. Spring tension of the switch contact can be destroyed by excessive solder.

The swing-out chassis on the right side of the instrument provides access to the side of the TIME/DIV and HORIZ DISPLAY switches. The top and bottom of these switches

can be reached for easier repair or removal by removing the B Sweep board (top) or the A Sweep board (bottom).

Power Transformer Replacement. The power transformer

in this instrument is warranted for the life of the instrument.

If the power transformer becomes defective, contact your

local Tektronix Field Office or representative for a warranty replacement (see the Warranty note in the front of this manual). Be sure to replace only with a direct replacement Tektronix transformer.

When removing the transformer, tag the leads with the

corresponding terminal numbers to aid in connecting the new transformer. After the transformer is replaced, check the performance of the complete instrument using the Performance Check procedure.

Power Chassis. The power transistors and other heat

dissipating power-supply components are mounted below the

Low-Voltage Regulator board. Remove the Low-Voltage Regulator board to reach these components. To reach the underside of the chassis, remove the fan through the rear

subpanel.

High-Voltage Compartment. The components located in

the high-voltage compartment can be reached for maintenance or replacement by using the following procedure.

1. Remove the bottom cover of the instrument as described

in this section.

2. Remove the high-voltage

3. Remove the three screws

high-voltage compartment.

shield. which hold the cover on the

4-11

TM 11-6625-1722-15

4. To remove the complete wiring assembly from the high-

voltage compartment,

unsolder the post-deflection anode

Iead (heavily insulated lead at side of compartment). The

other leads are long enough to allow the ossembly to be

lifted out of the compartment to reach the parts on the under side.

5. To replace the high-voltage compartment, reverse the

order of removal.

NOTE

All solder joints in the high-voltage compartment should have smooth surfaces.

Any protrusions

may cause high-voltoge arcing at high altitudes.

Recalibration After Repair

After any electrical component has been replaced, the

calibratian of that particular circuit should be checked, as

well as the calibration of other closely related circuits. Since the Iow-voltage supply affects all circuits, calibration of the entire instrument should be checked if work has been done in the low-voltage supply or if the power transformer has been replaced. The Performance Check procedure in Section 5 provides a quick and convenient means of checking instrument operation.

Instrument Repackaging

If the Type 453 is to be shipped for long distances by commercial means of transportation, it is recommended that the instrument be repackaged in the original manner for maximum protection. The original shipping carton can be

saved and used for this purpose. Fig. 4-5 illustrates how to repackage the Type 453 and gives the part number for the

packaging components if new items are needed. Fig. 4-6 illustrates how to repackage the Type R453 and the appli-

cable part numbers.

4-12

Fig. 4-5.

Repackaging the Type 453 for shipment.

TM 11-6625-1722-15

Fig. 4-6.

Repackaging the Type R453 for shipment.

4-13

TM 11-6625-1722-15

4-14

Fig. 4-7. Location of circuit boards in Type

453.

TM 11-6625-1722-15

Fig. 4-8.

4-15

TM 11-6625-1722-15

4-16

Fig. 4-9.

Partial Vertical

Preamp circuit

board.

Vertical

Switching

and partial Vertical

Preamp circuit shown.

TM 11-6625-1722-15

Fig. 4-10.

4-17

TM 11-6625-1722-15

4-18

Fig. 4-11.

Partial

A Sweep circuit board. A Sweep

Generatar

and

Calibrator

circuits

shown.

TM 11-6625-1722-15

Fig. 4-12.

4-19

TM 11-6625-1722-15

4-20

Fig. 4-13.

Partial B

Sweep circuit

Horizontal Amplifier and partial B

board.

Sweep

Generator

circuits shown.

TM 11-6625-1722-15

Fig. 4-14.

4-21

TM 11-6625-1722-15

4-22

Fig. 4-15. Z

Axis

Amplifier and High-Voltage Regulator

circuit

board.

TM 11-6625-1722-15

Fig. 4-16.

4-23

SECTION 5

PERFORMANCE CHECK

TM 11-6625-1722-15

Introduction

This section of the manual provides a procedure for rapidly checking the performance of the Type 453. This procedure checks the operation of the instrument without removing the covers or making internal adjustments. However, screwdriver adjustments which are located on the front panel are adjusted in this procedure.

If the instrument does not meet the performance requirements given in this procedure, internal checks and/or adjustments are required. See the Calibration section of this manual. All performance requirements given in this section correspond to those given in Section 1 of this manual.

NOTE

All waveforms shown in this section are actual

waveform photographs taken with a Tektronix

Oscilloscope Camera System unless noted other-

wise. Graticule lines have been photographically

retouched.

Recommended Equipment

The following equipment is recommended for a complete performance check. Specifications given are the minimum necessary to perform this procedure. All equipment is assumed to be calibrated and operating within the given specifications of the recommended equipment.

For the most accurate and convenient performance check, special Tektronix calibration fixtures are used in this procedure. These special calibration fixtures are available from Tektronix, Inc. Order by part number through your local Tektronix Field Office or representative.

1. Time-mark generator. Marker outputs, five seconds to 10 nanoseconds; marker accuracy, within 0.1%. Tektronix Type 184 Time-Mark Generator recommended.

2. Standard amplitude calibrator. Amplitude accuracy, within 0.25%; signal amplitude, five millivolts to 50 volts; output signal, one-kilohertz square wave and positive DC voltage; must have mixed display feature. Tektronix calibration fixture 067-0502-00.

3. Square-wave generator. Frequency, one and 100 kilohertz; risetime, 12 nanoseconds or less from high-amplitude

output and one nanosecond or less from fast-rise output;

output amplitude, about 120 volts unterminated or 12 volts

into 50 ohms from high-amplitude output-50 to 500 millivolts from fast-rise output. Tektronix Type 106 Square-Wave

Generator recommended.

4. Constant-amplitude sine-wave generator. Frequency, 350 kilohertz to above 50 megahertz; reference frequency, 50 kilohertz;

output amplitude, variable from five millivolts

to five volts into 50 ohms or 10 volts maximum unterminated;

amplitude accuracy, within 3% at 50 kilohertz and from 350

kilohertz to above 50 megahertz. Tektronix Type 191 Constant Amplitude Signal Generator recommended.

5. Low-frequency sine-wave generator. Frequency 60 hertz to one megahertz; output amplitude, variable from 0.5 volts to 40 volts peak to peak; amplitude accuracy, within 3% from 60 hertz to one megahertz. For example, General Radio 1310-A Oscillator (use a General Radio Type 274QBJ Adaptor to provide BNC output).

6. 10X probe with BNC connector. Tektronix P6010

Probe recommended.

7. Test oscilloscope. Bandwidth, DC to 50 megahertz; minimum deflection factor, five millivolts/division; accuracy,

within 3%. Tektronix Type 453 Oscilloscope recommended.

8. Current-measuring probe with passive termination. Sen-

sitivity, two milliamperes/millivolt; accuracy, within 3%. Tektronix P6019 Current Probe with 011-0078-00 passive termination recommended.

9. Cable (two). Impedance, 50 ohms; type, RG-58/U; length, 42 inches; connectors, BNC. Tektronix Part No. 012-0057-01.

10. BNC T connector. Tektronix Part No. 103-0030-00.

11. Cable. Impedance, 50 ohms; type, RG-58/U; length,

18 inches; connectors, BNC. Tektronix Part No. 012-0076-00.

12. Cable. Impedance, 50 ohms; type, RG-213/U; electrical length, five nanoseconds; connectors, GR874. Tektronix Part No. 017-0502-00.

13. In-1ine termination.

rating, two watts; accuracy, ±3%; connectors, GR874 input with BNC male output. Tektronix Part No. 017-0083-00.

14. Input RC normalizer. Time constant, 1 megohm X 20

pF; attenuation, 2X; connectors, BNC. Tektronix calibration

fixture 067-0538-00.

15. 5X attenuator. Impedance, 50 ohms; accuracy, ±3%; connectors, GR874. Tektronix Part No. 017-0079-00.

16. Dual-input coupler. Matched signal transfer to each input. Tektronix calibration fixture 067-0525-00.

17. Adapter. Adapts GR874 connector to BNC female connector. Tektronix Part No. 017-0064-00.

18. Termination. Impedance, 50 ohms; accuracy, ±3%; connectors, BNC. Tektronix Part No. 011-0049-00.

19. Adapter. Connectors, BNC female and two alligator

clips. Tektronix Part No. 013-0076-00.

20. Screwdriver. Three-inch shaft,

screws. Tektronix Part No. 003-0192-00.

Impedance, 50 ohms; wattage

5-1

TM 11-6625-1722-15

PERFORMANCE CHECK PROCEDURE

General

In the following procedure, control settings or test equip-

ment connections should not be changed except as noted.

If only a partial check is desired, refer to the preceding step(s). for setup information. Type 453 front-panel control

titles referred to in this procedure are capitalized (e.g.,

VOLTS/DIV).

The following procedure uses the equipment listed under Recommended Equipment. If equipment is substituted, control settings or setup may need to be altered to meet the requirements of the equipment used.

Preliminary Procedure

1. Connect the Type 453 to a power source which meets

the voltage and frequency requirements of this instrument.

2. Set the Type 453 controls as follows:

CRT controls

INTENSITY FOCUS

SCALE ILLUM

Vertical controls (both channels if applicable)

VOLTS/DIV VARIABLE POSITION

Input Coupling

MODE

TRIGGER

INVERT

Triggering controls (both A and B if applicable)

LEVEL SLOPE COUPLING SOURCE

Sweep controls

DELAY-TIME MULTIPLIER

A and B TIME/DIV

A VARIABLE

A SWEEP MODE

B SWEEP MODE

HORIZ DISPLAY

MAG

A SWEEP LENGTH

POSITION

POWER

Counterclockwise

Midrange

As desired

20 mV

CAL Midrange DC

CH 1

NORM Pushed in

+ AC INT

Fully counterclockwise 1 ms CAL AUTO TRIG TRIGGERABLE AFTER

DELAY TIME A OFF FULL Midrange off

Side-panel controls

B TIME/DIV VARIABLE CALIBRATOR

3. Set the POWER switch to ON. Allow at least 20 min-

utes warm up before proceeding,

1. Check Trace Alignment

REQUIREMENT-Trace parallel to horizontal graticule

lines.

a. Advance the INTENSITY control until the trace is visi-

ble.

b. Turn the Channel 1 POSITION control to move the

trace to the center horizontal line.

c. Adiust the FOCUS control for as sharp a display as

possible.

d. CHECK-The trace should be parallel with the center

horizontal line.

e. If necessary, adiust the TRACE ROTATION adjustment (on side panel) so the trace is parallel to the horizontal graticule lines.

2. Check Astigmatism

REQUIREMENT-Sharp, well-defined display. a. Connect the time-mark generator (Type 184) to the

Channel 1 INPUT connector with the 42-inch BNC cable.

b. Set the time-mark generator for output markers of 1

and 0.1 millisecond.

c. Set the CH 1 VOLTS/DIV switch so the large markers

extend beyond the bottom and top of the graticule area.

d. Set the A LEVEL control for a stable display. e. CHECK-Markers should be well defined with optimum

setting of FOCUS control.

f. If necessary, adjust the FOCUS control and ASTIG

adjustment (on side panel) for best definition of markers.

3. Check Y Axis Alignment and Geometry

REQUIREMENT-Y axis alignment, markers parallel to center vertical line within 0.1 division; geometry, bowing or tilt of markers at left and right extremes of display 0.1 division or less.

a. Set the horizontal POSITION control to move a large marker to the center vertical line.

b. CHECK-Markers parallel to the center vertical line within 0.1 division (see Fig. 5-1).

c. Set the horizontal POSITION and A VARIABLE controls so a large marker coincides with each vertical graticule line.

CHECK-Bowing and tilt of markers over entire dis-

area 0.1 division or less (see Fig. 5-1).

play

Disconnect all test equipment.

CAL 1V

5-2

Tektronix 453 schematic

Specifications and Main Features

Frequently Asked Questions

User Manual

WARNING

SECTION 1

SECTION 2

TABLE 2-1

SECTION 3

SECTION 4

TABLE 4-1

TABLE 4-2

TABLE 4-3

TABLE 4-4

SECTION 5