HP 175A Service manual

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OPERATING AND SERVICE MANU'AL

MODEL

SERIALS

PREFIXED:

175A

235

OSCILLOSCOPE

4

-

01526-1

Copyrieh)

1501

PAOt

HtWLtIT-PACKARO COMPANY

MILL

ROAD,

PAL0

ALlO,

0

CALIFORNIA,

1963

U.S.A.

Printed:

FEB

1963

Table of Contents Model 175A

Section

I

GENERALINFORMATION

1.1

.

Description

1.3 . Auxiliary EquipmeQt

1.5

.

Instrument Identification

1.7

.

Warranty

1.9

.

Special Features

1.11

.

Cathode-Ray Tube

1.13

.

Special Controls

I1

INSTALLATION

2.1

.

Incoming Inspection

2.2

.

MechanicalInspection

2.4

.

Performance Check

2.6

.

Installation

2.8

.

Rack Mounting

.

2.10

2.13

2.15

2.17

m

OPERATION

3.1

3.3

3.5

3.7

3.9

3.11

3.13

3.15

3.17

3.18

3.20

3.23

3.25

3.27

IV

PRINCIPLES

4.1

4.9

4.11

4.13

4.15

4.17

4.19

4.21

4.23

4.25 . Sweep Generator

4.27

4.30

cooling

.

Power Requirement

.

Safety Power Cable

.

Repackaging for Shipment

.............

.

General

.

Triggering

.

. .

.

Sweep Controls

.

. .

Horizontal Functions

.

Intensity Modulation

.

Overall FunctionDescription

.

Vertical Amplifier

.

. . . . .

.

.............

Beam Finder Calibration

Trigger Trigger Level Trigger Slope Sweep Mode

Sweep Time Sweep Magnifier

Step-by-StepProcedures

OF

Cross-Coupled Cathode Follower. 4-2 Differential Amplifier

Peaking

Sync Amplifier Delay Line Circuit Protection Scan Output

Trigger Generator SweepGeneratingcircuits

TABLE

*

...

Page

1-1 1-1 1-1 1-1 1-1

1-4 1-4 1-4

2-1 2-1 2-1 2-1 2-1 2-1 2-1 2-1 2-1 2-1

3-1 3-1 3-1 3-1 3-1 3-1 3-1 3-1 3-1 3-1 3-1 3-1 3-1 3-1 3-1

4-1 4-1 4-1

4-2 4-2

4-2 4-2 4-1 4-2 4-2 4-2 4-3

*

* . * *

...........

.......

....

...........

........

.......

........

............

.......

.....

......

..........

.........

............

......

.......

.....

.........

..........

...........

Source

........

.........

..........

.........

..........

........

.......

....

OPERATION

.

* . *

........

.....

............

........

..........

.......

..........

.........

......

OF

CONTENTS

Section IV PRINCIPLES OF OPERATION (Cont'd)

4.38

.

Single-Sweep Operation

4.40

.

4.43

4.47

4.51

4.53

4.55

V MAINTENANCE

5.1

5.3

5.5

5.7

5.9

5.11

5.14

5.20

5.21

5.22

5.23

5.24

5.25

5.27

5.29

5.31

5.33

5.35

5.40

5.47

5.53

5.58

5.59

5.61

5.64

5.67

5.68

5.70

5.77

5.81

5.87

5.93

VI

REPLACEABLE PARTS 6

.

1

6.4

Schmitt Trigger Circuit

.

Horizontal Amplifier

.

High-Voltage Power Supply

.

Intensity Control

.

Scale Control

.

Low-Voltage Power Supplies

.

Introduction

.

Servicing the

.

Performance Check

.

Test Equipment

.

Preliminary Settings

.

Horizontal Amplifier

.

Sweep Generator

.

Vertical Amplifier Bandwidth

.

Calibrator

.

Intensity Modulation

.

Sweep and Gate Output

(Option Feature)

.

Accessory Probes

.

Adjustments

.

Equipment Neededfor Adjustments 5-4

.

Locationof Adjustments

.

Preliminary Settings

.

Low-Voltage Power Supplies

.

High-Voltage Power Supply

.

Horizontal Amplifier

.

Sweep Generator

.

Vertical Amplifier

.

Calibrator

.

Repairs

.

Equipment Required

.

Procedure

.

Troubleshooting

.

Isolating Troubles to

Major Section

.

Low-Voltage Power Supplies

.

High-Voltage

.

Vertical Amplifier

.

Sweep Generator

.

Horizontal Amplifier

.

Introduction

.

Ordering Information

.........

............

...........

Air

Filter

.........

...........

..........

.............

..........

.........

........

Power

........

...........

.....

.......

....

........

......

.......

........

......

........

......

.......

....

......

.......

......

a

Supplies

.......

......

Page

...

. .

.

...

. .

.

4-4 4-4 4-5 4-6 4-6 4-6 4-6

5-1 5-1 5-1 5-1 5-1 5-1 5-1 5-2 5-3 5-4 5-4

5-4 5-4 5-4

5-4 5-4 5-5 5-5 5-8 5-10 5-11 5-12 5-12

5-13 5-13 5-13

5-13 5-13 5-16 5-16 5-17 5-18

6-1 6

.

1

6-1

ii

01526-1

Model 175A

LIST

OF

ILLUSTRATIONS

List of Illustrations

List of Tables

Number Title

1-1.

1-2. 3-1. 3-2.

3-3.

3-4. 3-5. 4-1.

4-2. 4-3.

4-4. 4-5.

4-6. 4-7. 4-8.

4-9. 5-1.

5-2. 5-3. 5-4.

5-5. 5-6. 5-7. 5-8. 5-9.

5-10. 5-11.

5-12. 5-13. ModLl 175A Component Locations, 5-14. Model 175A Component Locations,

Model 175A Oscilloscope with MOI !11750A

and Model 1780A Plug-In Cathode-Ray TubeWarranty. Model 175A Controls and Terminals Internal Sweep Magnified Sweep Probe Compensation

Intensity Modulation Overall Block Diagram of Model 175A

with Model 1750A Plug-In Vertical Amplifier Block Diagram Cross-Coupled Cathode Follower

Simplified Schematic Diagram Sweep Generator Block Diagram. Trigger Generator Simplified Circuit

and Composite Characteristic Simplified Schmitt Trigger Circuit. Horizontal Amplifier Block Diagram High-Voltage Power -Supply

Block Diagram.

Low-Voltage Power-Supply

Block Diagram. Test Plug Adjustments and Component Locations,

Top View Adjustments and Component Locations,

Bottom View. Pattern Adjustment. Frequency Compensation Attenuator Compensation Trigger Sensitivity Scan Balance Mid

-

Frequency Response

Preliminary Adjustment Mid-Frequency Response

Final Adjustment. High-FrequencyResponse Model 175A Component Locations,

T~D View

Bottom View. Right Side View

. . .

.

. . . .

.

. .

.

. .

. . . . . . . .

.

. . . . . . . . . .

.

. .

.

. . . .

.

Units

. . . .

.

. . . .

.

. .

. . . . .

Unit

. . . . . . . .

.

. . . . . .

. . . . . . .

. . . . . . . . .

. . . . . . .

. . .

. . . . . .

. . .

. . . . . . . . .

. . . . . .

.

. . .

.

. . . . .

. . . .

. .

.

. . . . . .

. . . . . . .

.

. .

. . .

.

. . . .

.

. .

.

. . .

. .

.

. . .

.

. .

.

. .

.

. . .

. . . .

.

1-0

1-2 3-0 3-2 3-3 3-4 3 -5

4-0 4-1

4-2 4-3

4-4 4-5 4-5

4-6 4-7

5-5 5-6 5-7

5-8 5 -9 5-10 5-10 5-11

5-12 5-12

5-12 5-19 5-20 5-21

Number Title Page

5-15. Model 175A Component Locations,

Left Side View

5-16.

A1

Vertical-Input Assembly

Component Locations

5-17. A2 Vertical-Output Assembly 5-18. Beam-Finder Switch S1, 5-19. Vertical Amplifier (schematic diagram) 5-25

5-20. A101 Sweep-Generator Assembly 5-21. A102 Trigger-Source Switch Assembly,

5-22. A103 Trigger-Level and -Slope Switch

5-23. Sweep Generator (schematic diagram) 5-27

5-24. 5-25. A1002 Sweep-Time Switch Assembly, 5-26. Sweep-Time Switch 5-27. A201 Horizontal Amplifier Assembly 5-28. A202 Horizontal Display Switch Assembly, 5-29. Horizontal Amplifier (schematic diagram)5 -31

5-30. A301 High-Voltage and Calibrator 5-31. A302 High-Voltage Deck Assembly 5-32. High-Voltage Power Supply and 5-33. A401 Low-Voltage Power Supply 5-34. Low-Voltage Power Supply. 5-35. Heater Circuit (schematic diagram

5-36. A701 Gate- and Sweep-Output Assembly 5-37. 5-38. Connectors

Component Locations Mounted Components

Component Locations Mounted Components Assembly, Mounted Components

AlOOl

Sweep-Switch Circuit Board

Component Locations Mounted Components (schematic diagram). Component Locations Mounted Components

Assembly Component Locations Component Locations Calibrator (schematic diagram). Component Locations (schematic diagram)

Component Locations

Gate

and Sweep Output

(schematicdiagram)

.

. . . . .

. . . . . .

. .

. . . . .

. . . . . . .

.

. .

. . . . .

. , . . . . .

.

. . .

. . . . . .

. .

. . . .

. . . . .

. . .

.

. .

. . . .

. . .

. .

. . . . . .

.

. . . .

.

. .

.

. . .

.

. .

.

. .

.

. .

.

5-21 5-23 5-24 5

-2

5-26 5 -26 5-26

5-28

5-28 5-29 5-30 5-30

5-32 5-32 5-33 5-34 5-35

5-36 5-36 5-36

5-37

5

LIST

Number Title Page

1-1.

Specifications

1-2. Associated Equipment and Accessories. 1-3

Test Equipment for Checks and

5-1. 5-2. Sweep Calibration

5-3. Power Supply Tolerances

01526-1

Adjustments

.

. .

. . . . . . . . .

.

. . . . . . . .

.

. .

.

. .

.

. .

. . . . .

. . .

.

1-1

5-0 5-3 5-5

OF

TABLES

Number Title Page

5-4. Sweep Time 5-5. Troubleshooting the Low -Voltage Supply 5-14 5-6. Vertical Amplifier Troubleshooting. 5-7. SweepGenerator Troubleshooting Guide 5-17

5-8. Horizontal Amplifier Troubleshooting 6-1. Index by ReferenceDesignator 6-2. Replaceable Parts

. . . . . .

.

. . .

.

. . . . .

. . . .

. .

5-11 5-17 5-18

6-2

6-13

iii

Section Figure

I

1-1

Model

175A

1-0

Figure

1-1.

Model

175A

Oscilloscope with Model

1750A

and Model

1780A

Plug-In

Units

01526-1

Model 175A

Paragraphs

Section

1-1

to 1-8

I

SECTION

GENERAL INFORMATION

1-1.

DES

C

R

I

PTI

0

N.

1-2.

The @ Model 175A Oscilloscope

general-purpose

width

of 50 megacycles and a 6 x 10 cm display. Optional plug-in units and accessories are available to increase the versatility of this instrument. Specifications are listed in table

1-3.

AUXILIARY EQUIPMENT.

Available associated equipment and accessories

1-4. are

listed

in table

a. Plug-Ins.

clude dual-trace and single-trace vertical amplifiers

which collectively cover 5 mv/cm to 20 v/cm sensitivities and dc to 50-mc bandwidth. Horizontal units include single sweep, sweep delay, a time-mark generator, and a display scanner.

test

instrument with a vertical band-

1-1.

1-2.

Plug-in units for the Model 175A in-

is

a calibrated

Table

1-1.

I

b.

Accessories. Each oscilloscope two Model 10003A (AC-21M) high-impedance probes and a detachable power cable.

1-5. INSTRUMENT IDENTIFICATION.

1-6. Hewlett-Packard uses serial number of the serial number on your instrument with those sheets supplied with the manual will define differences between your instrument andthe Model 175A described in this manual.

1-7. WARRANTY.

1-8. Both the cathode-ray tube carry Hewlett-Packard warranties. The

is

illustrated in figure 1-2, and a copy the back of this manual for your use in tube failure within the warranty period. The Model 175A warranty

Specifications

(000-00000).

on the

title

is

also at the back of this manual.

a

two-section eight-digit

If

page of this manual, change

is

supplied with

the

first

do

(crt)

and Model 175A

crt

is

three digits

the

not agree

warranty

included at

event of

SWEEP GENERATOR Internal Sweep:

24 ranges, 0.1 psec/cm to 5 sec/cm

nier

provides continuous adjustment between

ranges and extends slowest sweep to at least

12.5 sec/cm.

Magnification: X10 (*5%) Triggering:

Internal

below

External

from any signal 0.5 volt peak-to-peakor more.

Triggering Point:

Internal

going signal displayed on the crt graticule.

External

on either the positive- or negative-going portion of the vertical signal.

HORIZONTAL Bandwidth DC to 500 kc

Sensitivity:

2

ranges, 0.1 volt/cm and 1 volt/cm. Vernier provides continuous adjustment between ranges and extends minimum sensitivity to 10 volts per centimeter.

Input Impedance:

1

-

Vertical input signal (from 2 mm

1

mc to approximately 2 cm

-

Either capacitive-

-

Any level of positive- or negative-

-

Any level between +5 and -5 volts

AMP

LIFTER

megohm shunted by approximately 30 pf

or

*3%.

at

50 mc).

direct-coupled,

Ver-

VERTICAL AMPLIFTER Bandwidth: DC to greater than 50 mc

CALIBRATOR Type:

Approximately 1000-cycle square wave, approximately 3 psec rise time

Voltage:

2

ranges, 1 volt and 10 volts peak-to-peak,

*l%,

15°C to 35°C

CATHODE-RAY TUBE Type:

@

post accelerator, 12-kv accelerating potential. Type P31-AL phosphor standard. For other phosphors,

Graticule:

Internal, 6 x 10 cm, marked in centimeter squares. Major horizontal and vertical axes have 2-millimeter subdivisions.

Intensity Modulation:

Approximately +20-volt pulse of normal intensity

GENERAL Power Requirements:

115 or 230 volts ac mately 425 watts maximum (depends on plug-ins used).

see

OPTIONS.

will

*lo%,

50 to 60 cps, approxi-

blank trace

01526-1

1-1

Section

Figure

I

1-2

Model 175A

Table

1-1.

GENERAL (cont'd) Dimensions:

16-3/4 inches wide, 12-1/4 inches high, 24-3/8 inches deep overall; hardware furnished for quick conversion to 12-1/4-inch

x

19-inch rack mount,

22 inches deep behind panel.

Weight:

Net

approximately

70

lb

maximum (depends on

plug-ins used)

Plug-In Vertical Amplifiers:

($3

Model 1750A Dual Trace Vertical Amplifier,

40

dc to

@

Model 1751A Single Channel Vertical Ampli-

arx

fier,dc to 50 mc

@

Model 1752A High Gain Vertical Amplifier, dc to 18 mc

@

Model 1753A Single Channel Vertical Amplifier, dc to 40 mc

Specifications (Cont'd)

Plug-In Horizontal Time Base Units:

($3

Model 1780A Auxiliary Unit

@

Model 1781A Sweep Delay Unit

@

Model 1782A Display Scanner

@

Model 1783A Time-Mark Generator

Accessories Furnished;

Two probes, 10003A (AC-21M), division, one power cable

Accessories Available:

($3

1075A, 1075B (AC-83A) Viewing Hood

($3

Model 1115A Testmobile

($4

Model ultraviolet light source for illuminating the graticule and pre-sensitizing film

OPTIONS

02. Supplied with

07.

Supplied with

11.

Supplied with

08. Sawtooth Output (approximately -2.5 volts to +2.5 volts) and Gate Output (+5-volt pulse nominal, riding on a

1O:l

voltage

196B Oscilloscope Camera, includes

P2

phosphor

P7

phosphor

P11

phosphor

-

2.5 volt level).

HEWLETT-PACKARD CO. PAGE MILL

1-2

ROAD.

PAL0 ALTO. CALIF.

U.S.A.

Figure 1-2. Cathode-Ray Tube Warranty

01526-1

Model 175A Section I

Table

1-2

Table 1-2. Associated Equipment and Accessories

@

Model Name

Description

1750A

Dual Trace

Vertical Amplifier

1751A

1752A

Fast

High Gain

Rise Plug-In

Vertical Amplifier

1753A

Single Channel

Vertical Amplifier 1780A 1781A

Auxiliary Plug-In

Sweep Delay Generator

1782A Display Scanner

1783A

Time-Mark Generator Provides intensity modulating time markers synchronized with

Oscilloscope Camera Makes permanent record of oscilloscope trace on quick-develop-

~~ ~

1075A or

Viewing Hood 1075B (AC-83A)

Dual-trace and differential display, 0.05 v/cm to 20 V/Cm

sensitivity, 9 nsec rise time (dc to

40

mc bandwidth).

7-nsec rise time, (dc to 50 mc bandwidth), 0.05 v/cm to

20 v/cm sensitivity.

0.005 v/cm to 20 v/cm sensitivity, dc to 18 mc bandwidth. Dual-input differential display, single channel.

Single channel, single input, 0.05 v/cm to 20 v/cm sensitivity,

rise

9-nsec

time (dc to 40 mc bandwidth).

Single or normal sweep, manual or external arming.

to 10 cm of sweep delay.

0

Will

either trigger or arm main sweep. Horizontal display controlled by either main sweep or delaying sweep for all or part of trace. Delaying sweep rate 2psec/cm to

Provides output to operate conventional

1

sec/cm.

X-Y

recorder. Includes pen stabilizer for nearly constant writing rate. Approximately 30-mc bandwidth with 40-mc plug-in unit.

1,

sweep. Marker intervals 0.1,

or 10 psec.

ing Polaroid-Land film. Clamps quickly to oscilloscope bezel. Oscillo-Raptar fully corrected f/1.9 lens. Alphax #3 shutter, 1/100 to internal graticule of

1

second. Includes ultraviolet light to silhouette

crt.

Model 10351A Carrying Case available.

Shades crt screen from surrounding light sources.

1115A

Testmobile Holds oscilloscope in convenient position for viewing. Rolls on

4-inch rubber-tired wheels. Tilts instrument from 10" below to 20" above horizontal in 5" increments. Chrome plate. Folds compactly for shipment or storage.

10003A

(AC- 21M)

10002B (AC- 21C)

Voltage Probe (2 sup-

plied with Model 175A Oscilloscope)

Voltage Probe 10002A or

High-impedance

imately

4

Division ratiolO:l, input impedance approximately 10 megohms shunted

High-impedance

imately 5 Division ratio 50:

test

probe with flange-operated jaws and approx-

feet of shielded cable matched to oscilloscope input.

by

10

pf.

Maximum voltage rating 600 volts peak.

test

probe with flange-operated jaws and approx-

feet

of shielded cable matched to oscilloscope input.

1,

input impedance approximately 9 megohms

~~ ~

shunted by 2.5 pf. Maximum voltage rating 1000 volts peak.

10025A (AC-21J)

10035A

lOOlOA

lOOlOB lOOlOD

Low Frequency Probe

~~~~

Tip Assortment

Alligator jaw Pincer jaw

Banana

Provides straight-through connection to oscilloscope from circuit

test

points. Pushbutton operated jaws. Shunt capacity approxi-

mately 150 pf. Cable approximately

to binding post adapter Model

5

lOllOA

feet long. Requires BNC

or equivalent.

One each of the 10010 tips for 10002A/B or 10003A Probes lOOlOE Pin tip

lOOlOF

lOOlOG

Hook tip Spring tip

01526-1 1-3

Section I Paragraphs 1-9 to 1-14

Model 175A

1-9.

SPECIAL FEATURES.

1-10. Special features of the Model 175A include the Hewlett-Packard internal-graticule crt, PRESET triggering, BEAM FINDER, and a cabinet which

serves both bench- and rack-mount requirements. Optional plug-in units are provided for both the vertical and the time axis. The main vertical amplifier

rise

time

is

less

than 7 nanoseconds which provides

maximum versatility for present and future plug-ins.

1-11.

CATHODE-RAY TUBE.

1-12. The 12-kv post-accelerator type with the cule which eliminates parallax, and an aluminized

crt

used in the Model 175A

is

a multi-grid

@

internal grati-

phosphor. The gun structure provides a large

10 cm distortionless viewing area as well as extremely high deflection-plate sensitivity. No frontpanel astigmatism control

1-13. SPECIAL CONTROLS.

1-14. Special panel controls make the Model 175A easy to operate. With SWEEP MODE in PRESET, the

sweep will synchronize internally on nearly all signals. BEAM FINDER enables the operator to locate the beam when increases the maximum sweep rate to 10 nsec/cm, calibrated in

it

is

off screen. SWEEP MAGNIFIER

all

positions.

is

required.

6

x

1-4

01526-1

Model

175A

Paragraphs

Section

2-1

to 2-18

11

SECTION

INSTALLATION

2-1.

INCOMING

2-2. MECHANICAL INSPECTION. 2-3. Upon receipt of your Model 175A, check the

contents of the shipment against the packing inspect the instrument for any obvious damage received in transit. See warranty sheet at the back of

this

manual. Keep the packing material until per-

formance check 2-4. PERFORMANCE CHECK.

2-5. Check the performance of the Model 175A by making the manual. Use this check to verify cations and also inspection. Instructions for the plug-in units will be found in the individual manuals for these instruments.

2-6. INSTALLATION. 2-7. The Model 175A

lett-Packard cabinet, suitable for bench or rack mount. Top and bottom covers may easy accessibility to internal parts and adjustments.

2-8. RACK MOUNTING. 2-9. Parts necessary for rack mounting are pack-

aged with

a. Remove b. Remove

c.

Remove adhesive-backed trim strip from sides.

d. Attach filler strip along bottom edge of front

panel.

e.

Attach mounting flanges to sides with larger

notch toward bottom of instrument.

f.

Mount in standard 19-inch rack (mounting screws

not supplied).

Rear support must be supplied to the rack-.< mounted instrument to mechanical vibrations.

2-10. 2-11. The air filter in this instrument must receive

an oil coat before the instrument

use

to prevent excessive dirt from entering instrument

case. Recommended

No.

3

“Handi-Koter” sprayer cans at most heating-supply stores or through your Hewlett-Packard field sales engineer.

the

COOLING.

Filter Coat. This adhesive

INSPECTION.

has

been successfully completed.

tests

outlined in paragraph 5-5 of this

all

listed specifi-

as

part of an incoming quality-control

is

packaged in the new Hew-

be

removed for

instrument. Proceed as follows:

tilt

stand.

feet

(press foot-release button).

Note

if

it

is

to be subjected

is

placed in normal

is

Research Products Company

is

available in

list

and

II

2-12. The cooling fan and air filter are located at the rear of the Model 175A. Leaveat least two inches of clearance behind the instrument for the free move-

ment of air. In rack installations be sure that the

recirculation of warm not result in high ambient temperature. Inspect the

air

filter periodically and clean pears to be reducing the flow of cooling section V for cleaning instructions.

2-13. POWER REQUIREMENT. 2-14. The Model 175A operates on 115 or 230 volts

*lo%,

the plug-ins used, but will not exceed approximately 425 watts. Before connecting the instrument to the power source, be sure

rear

proper fuse

2-15. SAFETY POWER CABLE. 2-16. To protect operating personnel the National

Electrical Manufacturers’ Association (NEMA) recommends that the instrument panel and cabinet be grounded. This instrument conductor power cable which grounds the instrument when plugged into an appropriate outlet. The offset round pin on the power-cable three-prong connector

is

when operating the instrument from a two-contact outlet, use a three-prong to two-prong adapter and connect the green pigtail on the adapter to ground.

2-17.

2-18. To repack the Model 175A for shipment, always

use the best packaging methods available. If the original container with is sales office for packing materials or instructions. The following steps are a general guide:

the instrument.

ment”.

50

to

60

panel

Connecting to a 230-volt source with the switch in the 115-volt position can result in damage to the instrument.

the ground pin. To preserve the protection feature

not on hand, consult your nearest Hewlett-Packard

a. Wrap the instrument in heavy paper.

b.

Protect the panel with cardboard strips.

c.

Use a strong cardboard or wooden

d. Use ample packing material around all sides of

e.

Seal with heavy tape or metal bands.

f.

Mark the container “Fragile - Delicate Instru-

is

in the correct position, and that the

is

installed (see section VI).

REPACKAGING FOR SHIPMENT.

air

within the rack cabinet does

it

as soon as

cps. Power required dependsupon

that

the 115-230 switch on the

CAUTION

is

equipped with a three-

its

packing pads and fillers

air.

it

apSee

box.

01526-1

2-

1

Section

Figure

111

3-1

SWEEP

OCCURRENCE

Model 175A

POWER switch and indicator light. The 115-

1.

230 volt switch

CALIBRATOR. Provides 1-volt and 10-volt

2.

is

located on

rear

square waves for calibration purposes and for probe compensation.

SCALE. Rotates

3.

graticule of

4.

INTENSITY. Adjusts brightness of

crt.

trace

to align

it

with internal

trace.

intensity-modulation input and switch cated on

5.

FOCUS. Adjusts sharpness of trace; no panel astigmatism control

BEAM FINDER. Locates

6. TRIGGER SLOPE. Permits triggering sweep

7.

rear

panel.

is

needed.

trace

when off screen.

on either positive- or negative-going slope of

trigger-source waveform.

TRIGGER LEVEL. Adjusts point on trigger-

8.

source waveform

TRIGGER SOURCE. Selects LINE, INTernal,

9.

at

which triggering occurs.

EXTernal AC, or EXTernal DC.

Figure

3-1.

panel.

An

are

lo-

Model 175A Controls and Terminals

10. SWEEP MODE. Selects triggered or free-running sweep. stable

11.

TRIG INPUT. Trigger signal input when

triggering with nearly

TRIGGER SOURCE

A

PRESET position provides

all

signals.

is

in EXTernal.

12. HORIZ INPUT. Input for external horizontal

signal.

13.

HORIZONTAL DISPLAY. Selects source of horizontal signal and horizontal sensitivity, including SWEEP MAGNIFIER X10.

14. EXTERNAL VERNIER. Adjusts external hori-

zontal sensitivity between calibrated steps of HORIZONTAL DISPLAY.

15. HORIZONTAL POSITION. Adjusts position of

trace

horizontally; vertical controls

are

on

panel of plug-in unit.

16. SWEEP TIME. Selects calibrated sweep in 1-2-5 steps from 0.1 pSEC/CM to 5 SEC/CM.

17. VERNIER. Adjusts sweep

rate

between

cali-

brated steps of SWEEP TIME switch.

3-0 01526-1

Section Paragraphs 3-1 to 3-28

111

Model 175A

SECTION

OPERATION

3-1. GENERAL.

3-2. The front panel labeling of the Model 175A closely describes the function of each control. The instrument and compatible test probes are provided. Vertical

controls are on the panel of the vertical plug-in unit. Their operation instrument.

3-3. BEAM FINDER. 3-4. BEAM FINDER locates the trace when

otherwise be off the screen. Depressing this button brings the trace on the screen, defocused and intensified. The POSITION controls can then be adjusted to bring the trace to the center of the screen.

3-5. CALIBRATION. 3-6. The CALIBRATOR amplitude

1%

from 15°C to 35°C (50°F to 95°F). Square-wave outputs are provided at an amplitude of and a frequency of approximately

3-7. TRIGGERING.

3-8. Four front-panel controls affect the start of the normal sweep. They are the TRIGGER SOURCE switch, TRIGGER LEVEL control, TRIGGER SLOPE switch, and SWEEP MODE control.

3-9. TRIGGER SOURCE. 3-10. The TRIGGER SOURCE switch selects the

source of the sweep trigger: the power line (LINE), the signal applied to the vertical amplifier (INT), or an external signal applied to TRIG INPUT (EXT AC or EXT DC). With INT lected, the trigger signal generator. With EX” DC selected, the trigger signal

is

3-

11.

3-12. The TRIGGER LEVEL control selects the voltage level on the trigger signal at which the sweep

starts. The control provides continuous adjustment of the trigger level from about -5 volts to about +5 volts on external trigger signals and over a range equivalent to internal trigger signals.

3-13. TRIGGER SLOPE. 3-14. TRIGGER SLOPE determines whether the sweep

starts

of the trigger signal. 3-15. SWEEP MODE.

3-16. The SWEEP MODE control determines whether the sweep requires a trigger or free runs. The control

is

has

a rise time of less than 7 nanoseconds,

is

described in the manual for that

it

might

is

accurate to

1

and 10 volts

1

kc.

or EXT AC triggering se-

is

ac-coupled to the sweep

dc-coupled to the sweep generator.

TRIGGER LEVEL.

6

centimeters of vertical deflection on

on the positive-slope or negative-slope portion

continuously adjustable with a switched position

111

(PRESET) at

PRESET triggering condition

triggered functions.

it

may be desirable to move the control out of PRE-

SET.

3-17. SWEEP CONTROLS,

3-18. SWEEP TIME. 3-19. There are 24 positions of the SWEEP TIME

control, from

to *3%. Intermediate (uncalibrated) sweep times

may be obtained by adjusting sweep time VERNIER. 3-20. SWEEP MAGNIFIER.

3-21. In the INT SWEEP TAL DISPLAY the basic sweep time by the setting of the SWEEP TIME switch. In the X10

magnified position the displayed sweep

faster, accurate to

scale

by

magnified signal

across; however, HORIZONTAL POSITION has enough

range to permit any portion of the presentation to be positioned on screen.

3-22. On the fastest sweep time, 0.1 pSEC/CM X10

(10 nsec/cm) do not use the time-scale measurements since small non-linearities

may exist. Due to the delayinthe vertical amplifier, this portion of the trace precedes the actual triggering point of the waveform. trace

is position of SWEEP TIME, the be used.

3-23. HORIZONTAL FUNCTIONS.

3-24. HORIZONTAL DISPLAY performs three external horizontal input functions: it selects external input, sets the sensitivity to 0.1 v/cm or arranges the input circuit for ac or dc coupling.

3-25. INTENSITY MODULATION.

3-26. INTENSITY MODULATION controls are on the rear panel of the Model 175A (see figure 3-5). itive 20-volt pulse intensities.

3-27. STEP-BY-STEP PROCEDURES. 3-28. Figure 3-1 briefly describes the function of

each of the Model 175A controls. cedures for a few basic operations are given in figures 3-2 through 3-5. Included are instructions for compensating the probes. The numbers on each control refer the illustration.

its

counterclockwise extreme. The

is

best for nearly all

At

some discrete frequencies

5

SEC/CM

10 to obtain the actual sweep time. The

is

positioned off screen in the 10 pSEC/CM X10

to

the corresponding step in the text below

to

0.1

~SEC/CM,

X1

position of HORIZON-

is

*5%.

Divide the SWEEP TIME

actually 10 screen diameters

first

5 cm of trace for

As

long as the

full

10-cm display may

will

blank the trace at normal

Step-by-step pro-

accurate

that

indicated

is

10 times

first 5 cm of

1

v/cm, and

A

pos-

01526-1

3-

1

Section

Figure 3-2

111

SWEEP

OCCURRENCE

1

Model

175A

Set INTENSITY MODULATION (rear panel) to

1.

INT and SWEEP OCCURRENCE to NORMAL. Set HORIZONTAL DISPLAY to INT SWEEP X1.

2. Set TRIGGER SOURCE to INT.

3.

Set SWEEP MODE to PRESET.

4.

If

5.

6.

7.

8.

9.

3-2 01526-1

signal amplitude

TIVITY to 20 VOLTS/CM. Connect signal to vertical INPUT.

If trace Adjust HORIZONTAL, VERTICAL POSITION. Release BEAM FINDER, adjust FOCUS and IN-

TENSITY. Increase sensitivity,

is

not visible, depress BEAM FINDER.

is

unknown,

set

SENSI-

if

necessary

Figure 3-2. Internal Sweep

to trigger sweep, and readjust POSITION

controls to center trace.

10. For vertical amplitude measurements, sensitivity VERNIER to CALIBRATED.

11.

Set SENSITIVITY for a vertical display tween 2 and 6 centimeters high.

12. Set TRIGGER SLOPE to trigger onpositive-

or negative-going slope of signal,

13. Adjust TRIGGER LEVEL, stable triggering.

14. If time-scale measurements

set

sweep time VERNIER to CAL.

15. Set SWEEP TIME for horizontal display as desired.

as

if

necessary, for

are

to be made,

set

be-

desired.

Model

175A

INTENSITY

@

BEAM FlNDfR

-

TRIGGEff

TRIGGER

SLOPE

LEVEL

Section

III

Figure 3-3

__

. . . .

t

SWEEP

WE

TRIGGER

SOURCE

Set controls as in figure 3-2.

1. Set HORIZONTAL DISPLAY to INT

SWEEP

X10.

2. Adjust HORIZONTAL POSITION to view any part of the display. Do

5

cm of fastest magnified sweep (0.1

not make time measurements in the first

pSEC/CM

X10).

Figure 3-3. Magnified Sweep

01526-1 3- 3

Section

Figure

111

3-4

-

UNDERCOMPENSATED

-

CORRECTLY COMPENSATED

-

OVERCOMPENSATED

Model 175A

SWEEP

PLUG-IN

OCCURRENCE

69

IlMCLL

Connect probe to vertical INPUT and touch

7. tip to 10 VOLTS CALIBRATOR.

8.

Holding rear flange of probe, loosen locknut. Holding vinyl sheath

9.

at

rear of probe, rotate

rear flange to obtain illustrated square wave.

AUXILIARY

LO<.

1.

Set SWEEP TIME to 0.5 MSEC/CM. 6. Set SENSITIVITY to 0.2 VOLTS/CM.

2.

Set HORIZONTALDISPLAY to INTSWEEPXl.

3.

Set TRIGGER SOURCE to INT.

Set SWEEP MODE to PRESET.

4.

3-4

5.

Set TRIGGER LEVEL to

0.

Figure

10. Tighten locknut.

3-4.

Probe Compensation

01526-

1

Model

175A

Section

III

Figure 3-5

INTENSITY

Connect modulating voltage to INPUT (+20 volts will

1.

blank trace

2.

Switch to EXTERNAL.

MODULATION

at

normal intensity).

Figure 3-5. Intensity Modulation

LD-

5-

687

LD-S-688

01526-1

3-

5

Section Figure

IV

4-1

VERTICAL

PRESENTATION

9

\

CHANNELA

CHANNEL

B

Model

175A

I

Q

[SENSITIVITY1

I

I I

9

1-1

I

!Qm]

\

‘.C

;;I

I

,I

I

I.,

’

I

TRACE

AMPLIFIER

I

9

[VERTICAL

4

POSITION/

VERTICAL

AMPLIFIER

\

7--

I

ro

CRT

vmn

CA

D

Ef

PL A TES

L

€C

nON

-1

I

4-0

Figure

4-1.

Overall

Model

Block

1750A

Diagram

Plug-In

of

Unit

Model

175A

with

01526-1

Model

175A

Section

Paragraphs 4- 1 to

4-

IV

10

SECTION

PRINCIPLES

4-1.

OVERALL FUNCTIONAL DESCRIPTION.

4-2. The Model 175A consists of a high- and a lowvoltage supply, a vertical and

a

sweep generator and a calibrator. Bothpower sup-

plies are regulated, tions include a gate- and sweep-output circuit not included in the standard instrument. Figure 4-1 shows the main functional units and controls. a dual-trace plug-in amplifier has been shown as part of the diagram. The circuits of the plug-in units are described in the manuals for those instruments. Circuit diagrams

5-19 to 5-38.

4-3. VERTICAL AMPLIFIER. The vertical amplifier delays the signal received from the dual-trace amplifier and applies the amplified signal to the vertical deflection plates of the crt. Before the signal is

signal to the sweep generator for internal triggering

of the sweep. 4-4. SWEEP GENERATOR. The sweep generator

accepts a trigger signal from an internal or external

source and generates a fast-rising trigger which

synchronized with the trigger signal. The trigger

starts

the beam horizontally across the crt screen. The

sweep generator thus provides a linear time base on

which to measure the vertical signal. The sweep

generator also provides an unblanking pulse to turn on the crt beam during the sweep.

4-5. HORIZONTAL AMPLIFIER. The horizontal

amplifier converts the internal sweep or external

a

block diagram of the instrument illustrating

delayed, the vertical amplifier applies part of the

the linearly rising sweep voltage which drives

of

the

as

Model

a

horizontal amplifier,

is

the dc heater supply. Op-

For clarity,

175A are shown in

figures

is

IV

OF

OPERATION

signal

the signal to the level required deflection plates of the crt.

4-6. CALIBRATOR. The calibrator multivibrator generates a square wave of about and 10-volt outputs.

4-7. HIGH-VOLTAGE POWER SUPPLY. The highvoltage power supply cuit which generates the three regulated dc voltages required for operation of the crt.

4-8. LOW-VOLTAGE POWER SUPPLIES. Operating voltages for all the oscilloscope circuits, including the high-voltage supply, are provided low-voltage power supplies. regulated.

4-9.

4-10. The vertical amplifier anced differential amplifier. The block diagram shown in figure 4-2. The amplifier receives the balanced signal from the plug-in vertical amplifier, amplifies the signal, and drives the vertical deflection plates of the line which delays the vertical signal 0.2 psec before applying the delay line, the signal from one side of the amplifier generator for internal triggering of the sweep. This

starts

signal at the crt deflection plates. The delayed signal 5105 for use in the Model 1782A Display Scanner.

from unbalanced to balanced, and amplifies

to

drive the horizontal

1

kc with 1-volt

is

an

rf

oscillator-rectifier cir-

All

dc voltages are

VERTICAL AMPLIFIER.

is

a conventional bal-

crt.

The circuit includes a delay

it

to the vertical plates of the crt. Prior to

is

sampled, amplified and applied to the sweep

the sweep in advance of arrival of the vertical

is

also applied to horizontal plug-in connector

by

the

is

CATHODE

DELAY

LINE

VERTICAL INPUT

SIGNAL

FROM

PLUG-IN

01526-1 4-1

CATHODE

FOLLOWER

INPUT

AMPLIFIER

Figure 4-2. Vertical Amplifier Block Diagram

CATHODE AMPLIF I ER

-

FOLLOWER

v3

TRIGGER SIGNAL

TO SWEEP GENERATOR

THROUGH TRIGGER-SOURCE

+

A

SWITCH

SI02

v4

FOLLOWER

--*

DRIVER

v7

OUTPUT

AMPLIFIER CATHODE-RAY TO

CATHODE

FOLLOWER

-

I

CAL

VERT

OUTPUT

TUBE

DISPLAY

SCAN NE

R

Section

IV

Paragraphs 4-11 to 4-29

Model 175A

INPUT+

---

I

V6A

U

INPUT+

t

+V

Figure 4-3. Cross-Coupled Cathode Follower

Simplified Schematic Diagram

4-11. CROSS-COUPLED CATHODE FOLLOWER. 4-12. Input stage

cross-coupled cathode followers. The simplified schematic

is cathode follower circuit provides driving source for the following stage. quencies, the stage acts as High frequency signals appearing readily pass through coupling capacitors to the opposite cathode. Since these high-frequency signals are in phase with the signals

add to the current available to the load. The decrease

in load impedance at high frequencies

pensated by the increase in high-frequency current offered by the cross-coupled cathode follower. plate and cathode resistors are the same value, there-

fore voltages in amplitude and the signals are effectively added in

parallel. Since the plate and cathode signals are

added at high frequencies, the effective output imped-

ance

is

reduced.

4- 13. DIFFERENTIAL AMPLIFIER.

4-14. Input amplifier

differential amplifiers. An unbalanced signal applied to one grid will appear at both plates balanced amplified. Common-mode signals, such as hum, at

V1,

as

well

as

V3 and V7, are

shown in figure 4-3. The cross-coupled

a

low impedance

At

a

simple cathode follower.

at

the plate circuits

at

the opposite cathode, they

low fre-

is

partly com-

The

at

the plates and cathodes are equal

V2

as well

as

V4 and V7 are

and

the grids the circuit of amplifier V4, cathode degeneration

are

reduced in magnitude at the plates.

In

is

introduced by Gain control R45, reducing the gain of

the stage.

4-15. PEAKING. 4- 16. Series and shunt peaking are provided through-

out the amplifier to extend the bandwidth while maintaining optimum transient response. Coils L7 and L8

adjust high-frequency response. Capacitors C22 and

C35, which remove cathode degeneration in the circuits of V4 and V7

provide a means of adjusting mid-frequency

as

signal frequency increases,

and

low-frequency response. 4-17. SYNC AMPLIFIER.

4-18. The sync amplifier

is

composed of two cathode

followers (input and output) and two amplifiers. The

sync amplifier samples the signal prior to the vertical amplifier delay line and delivers this amplified signal to the trigger generator to start the sweep. Since the signal in the vertical amplifier

is

delayed 0.2 p sec

after the sync amplifier pick-off point, the sweep is

able to

start

before the vertical signal reaches the

crt deflection plates. 4-19. DELAY LINE.

4-20. The delay line

is

constructed to provide

0.2 psec delay. The internal impedance of input amplifier and R24

V2

in parallel with plate load resistors R23

is

designed to match the impedance of the delay line in order to minimize reflections. The delay line

is

peaked with L13 and L14 for optimum tran-

sient response. 4-21. CIRCUIT PROTECTION.

4-22. Diodes CR1,

2,

3, and 4 prevent the gridcathode voltage of V3 and V7 from becoming excessive during turn-on time.

4-23. SCAN OUTPUT. 4-24. Cathode follower V10 provides low-impedance

output to the horizontal plug-in connector for use with the Model 1782A Display Scanner. R71-R73 and R74-R72, reduces the dc level

A

balanced divider,

at

the plates of V7 to approximately zero volts; C36 and C37 compensate the divider

at

high frequencies.

C33 balances the high-frequency scan output.

4-25.

SWEEP

GENERATOR.

4-26. The sweep generator consists of sweep-generating circuits plus an amplifier and trigger generator which actuate the sweep-generating circuits. diagram of the sweep generator

is

shown in figure 4-4.

A

block

4-27. TRIGGER GENERATOR.

4-28. The trigger signal is applied through differential driver

YlOl

to trigger-generator tunnel diode

CR102 and amplifier Q103. TRIGGER SLOPE and

TRIGGER LEVEL controls are in the driver circuit. 4-29. The trigger generator

as

a

bistable device to convert

wave shape to

a

rectangular wave with very

is

a

tunnel diode acting

an

input signal of any

fast

a

4- 2

01526-1

Model 175A

-IOOV

'

Section IV

Paragraphs 4-30 to 4-33

TIMING

SWITCH

SWEEP HOLD-OFF

TIME RELATION

BETWEEN SWEEP

AND HOLD-OFF

A

4

nx

GATE OUTPUT

BIAS-CONTROL

CATHODE

FOLLOWER

VI09

I

/

I

SWEEP MODE

1

FOLLOW CATHODE ER

V105A

TIMING

CAPACITOR

HOLDOFF

CAPACITOR

-IOOV

I

-i?Nf

f4

I

CATHODE

I

FOLLOWER

I

-1

-

I

-&/I

f

VI07

4b-b

CATHODE

FOLLOWER

VI058

A

t

SWEEP OUTPUT

BO-

L-331

Figure 4-4. Sweep Generator Block Diagram

switching times. A simplified circuit

is

shown in figure 4-5A, and the composite characteristic of this circuit characteristic

is

illustrated in figure 4-5B. The composite

is

the sum of the currents through the tunnel diode and through the Sensitivity control. Because the tunnel diode

a

negative resistance region while the Sensitivity control justed to

is

a linear device, Sensitivity can be ad-

alter

the shape of the curve in figure 4-5B,

is a non-linear device with

achieving narrow switching limits between points D and E. The Symmetry control adjusts the total current halfway between switching points D and E. trigger signal varies through voltage follow the path CDGFEBC, producing the

to

the circuit, establishing bias line CF,

its

cycle, current and

As

rec-

the

tangular trigger output. The inductor sharpens the

rise and fall times of the square wave by preventing

fast

current changes through the Sensitivity con-

trol. Points A and

the trigger signal put

of

the trigger generator

H

represent the signal limits when

is

larger than necessary. The out-

is

differentiated by transformer T103, and the resulting sharp pulses actuate the gate generator.

4-30. SWEEP GENERATING CIRCUITS.

4-31. Gate generator V103/V104A

is

a

Schmitt

cir-

cuit with wide hysteresis limits. Between sweeps,

the A section of bias control cathode follower VI09 holds the bias at the input of thegate generator close to the lower hysteresis limit.

The trigger generator applies both positive and negative triggers. The positive triggers

are

reduced in amplitude by clipper diode CR103 and have no effect, but a negative pulse drives the input to the gate generator below the lower hysteresis limit and causes the gate generator to switch

4-32. When gate generator V103/V104A switches,

(see

paragraph 4-40).

it

provides positive and negative gates. The positive gate

is

applied to the high-voltage power supply through the horizontal plug-in to turn on the crt beam. The negative gate applies reverse bias to switchdiode

CR106. Prior to the gate, the switch diode

is

forward biased and holds the input to integrator V106 at about -4 volts. The negative gate opens the diode switch and frees the input to the integrator.

4-33. Once freed, the input to integrator V106 starts going negative since it

is

connected to

-100

volts

through the sweep-time resistor (figure 5-23). The

integrator amplifies and inverts its input to produce

a

large, positive-going output which

is

applied back to the input through cathode follower V107 and the sweep capacitor (figure 5-23).

As

a result, the

01526-1

4-3

Section IV Paragraphs

A.

CIRCUIT

I

5.5

uc?

4-34

to

0

4-41

+V

4

I

W-LI

OUTPUT

TRIGGER

SYMMETRY

Model

175A

diode

CR106.

integrator

The switch diode returns the input of

V106

to its pre-sweep level, discharging

the sweep capacitor.

4-35.

During a sweep time, hold-off cathode follower

V105B

ends, this capacitor

V103/V104A

charges a hold-off capacitor. After the sweep

lets

the input to gate generator

down slowly enough to prevent that circuit from being triggered again until the remaining sweep circuits have recovered completely. The SWEEP TIME switch changes the size of the hold-off capacitor with sweep time.

4-36.

Clamp

from the same voltage level, about

4-37.

The SWEEP MODE control determines the no-signal bias erator tion of bias control cathode follower

V104B

V103jV104A

ensures that each sweep starts

-50

volts.

R172

at

the input to gate gen-

by setting the

(figure

bias

on the A sec-

V109.

5-23)

With the control set to PRESET or in the TRIGGER portion of its adjustable range, the gate generator bias cannot drop below its lower hysteresis limit unless the trigger generator provides a trigger. With the control set in the FREE RUN portion of its adjustable range, the gate bias teresis limit. Thus

is

allowed to drop below its lower hys-

as

the hold-off capacitor

dis-

charges, it lets the gate generator bias all the way down to the lower hysteresis limit, and another sweep starts automatically.

-

V

LD-

Y

-

643

8.

Figure

I

COMPOSITE CURVE

4-5.

Trigger Generator Simplified Circuit

and Composite Characteristic

V106

change in voltage at the input to integrator ing the sweep time

is

only about one volt. Voltage

dur-

across the sweep resistor, then, changes by about

1%,

and the current through the resistor changes by the same amount. The current through the sweep resistor

is

the charging current for the sweep capacitor; therefore, the voltage across the sweep capacitor changes quite linearly with time, and the sweep signal

is

a nearly linear voltage ramp. The SWEEP TIME switch changes the value of sweep resistor or capacitor to change the sweep time. The sweep output

is

applied to the horizontal amplifier through the

horizontal plug-in.

4-34.

An

attenuated sweep signal is applied to the input of gate generator cathode follower cathode follower

V105B

V109.

V103, V104A

through hold-off

and section B of bias control

This signal drives the input of the gate generator up to the upper hysteresis limit and causes the gate generator to switch back to its

pre-sweep state. The gate generator then ends the the gates, blanking the crt and forward biasing switch

4-38.

SINGLE-SWEEP OPERATION,

4-39.

The SWEEP OCCURRENCE switch (on the panel of the horizontal plug-in unit) selects normal or single-sweep operation. Normal operation

is

discussed above. For single-sweep operation, the SWEEP OCCURRENCE switch converts Schmitt circuit. cathode follower

As

the sweep signal from hold-off

V105B

rises

to end the gate from

V109

into a

the gate generator, the sweep signal also switches the Schmitt circuit of and

V109A

is

cut off. The B section of holds the input to gate generator enough

so

that triggers from the trigger generator

V109

so

that

V103/V104A

V109B

conducts

V109

then high

cannot actuate the gate generator, and the sweep generating circuits are effectively disabled. itive signal applied to circuit of

V109

so

cut off. The A section of

that

V109A

V109

switches the Schmitt

conducts and

then sets the input to

A

pos-

V109B

is

the gate generator according to the setting of the SWEEP MODE control, and the sweep generating circuits are effectively armed. The switching signal for

V109.4

can be an external signal applied to the ARMING INPUT connector or an internal signal obtained by switching SWEEP MODE control out of its PRESET position.

4-40.

SCHMITT TRIGGER CIRCUIT.

4-41.

The Schmitt trigger circuit

is

a form of bistable multivibrator used where fast-rising signals are required. Figure

4-6

shows a simplified Schmitt trigger circuit and input and output waveforms. If initially the input voltage is such that

V2

conducts.

itive, it

As

the input voltage becomes more

will

eventually reach a predetermined level

(a) at which the circuit changes state;

V1

is

cut off,

pos-

conducts

4- 4

01526-

1

Mxlel

175A

Section

Paragraphs 4-42 to 4-46

IV

E+

c

VI

I

INPUT

-9

P--

OUTPUT

Figure

4-6.

Simplified Schmitt Trigger Circuit

Et

+

SD-u-79

4-43.

4-44. The horizontal amplifier amplifies the internal sweep or an external signal applied to the horizontal INPUT connector and drives the horizontal deflection plates of the crt. Figure diagram of the horizontal amplifier. The internal

sweep signal DISPLAY switch to cathode follower V203A. From V203A the signal passes through cathode follower V203B to one input of differential amplifier V204V205. The other grid of the differential amplifier

returned to ground through a resistance. The differential amplifier amplifies the difference between its two input signals (one of which vides output cathode followers V208A and V208B. These cathode followers drive the crt deflection plates. The cathode followers also drive capacitance driver V209 which acts cathode followers. When high-speed signals such the faster sweeps drive the crt beam from right, the capacitance driver discharges the capacitance of the crt deflection plates.

4-45.

PUT connector pass through an attenuator, amplifier V201A-B, and the HORIZONTAL DISPLAY switch to cathode follower V203A. Otherwise the operation the same signal.

HORIZONTAL

is

a

balanced output signal which

as

the cathode resistance for the output

External horizontal signals applied to the

as

described above for the internal sweep

AMPLIFIER.

4-7

is

a

simplified block

applied through the HORIZONTAL

is

ground) and pro-

is

applied to

left

is

as

to

IN-

is

and V2 tive, the common cathode potential decreases and V2 grid goes positive. When the input reaches second predetermined level circuit of the circuit negative depending upon the slope of the input.

4-42.

trigger switches are the hysteresis limits. Note that the circuit does not switch unless the input crosses both limits.

HORIZ

INPUT

is

cut off.

switches back to

The input voltage levels

*

If

the input voltagethengoes nega-

(b),

its

initial state.

is a voltage step, either positive or

EXTERNAL

INPUT

AMPLl

v201

F I ER

-+

GENERATOR

V2

conducts and the

at

which a Schmitt

C

ATH 0 DE

FOLLOWER

V203A

4

INPUT

FROM

SWEEP

The output

CATHODE DIFFERENTIAL

FOLLOWER

V203B

1

I

4-46. The HORIZONTAL DISPLAY switch selects the signal to be applied to the horizontal deflection plates. The switch also controls the input attenuator and the

a

sweep magnifier. The sweep magnifier attenuator between V203A and V203B provides expansion. The EXTERNAL VERNIER control varies the series resistance between V201A and V201B and thereby varies the output of V201B. The range of the EXTERNAL VERNIER tinuous adjustment of external horizontal sensitivity between the calibrated settings of the HORIZONTAL DISPLAY switch. switch

-+

AMPLIFIER

V204,

is

in the common cathode circuit of V204 and

V205

is

sufficient to provide con-

A

section of the BEAM FINDER

OUTPUT OUTPUT

CATHODE

-+

FOLLOWER RAY

V208 TUBE

T

CAPACITANCE

DRIVER

V209

a

means of sweep

CATHODE

I I

t

I

TO

01526-1

Figure 4-7. Horizontal Amplifier Block Diagram

4-5

Section

W

Paragraphs 4-47 to 4-56

Model 175A

V205. When pressed, the switch reduces the gain

so

that an unbalance prior to V204 and V205 cannot de-

flect the crt beam off the screen.

4-47.

HIGH-VOLTAGE POWER SUPPLY.

4-48. The high-voltage supply provides the operating voltages for the crt. voltage power supply

50-kc output

of

voltage transformer T301. up the oscillator output to high

A

block diagram of the high-

is

shown in figure 4-8. The

rf

oscillator V301

is

applied to high

The transformer steps

ac

voltages which rectifiers V304, V305, and doubler stage V302 and V303 convert to dc.

The dc voltages

are

then sup-

plied to the crt. 4-49. Control of the high-voltage supply

is

accom-

plished by comparing the -2700 volts supplied to the

crt cathode with +370 volts from the regulated lowvoltage power supply. ply produce an error voltage which the dc control amplifier V306A-B and the oscillator

as

Changes in the -2700 volt sup-

is

amplified by

is

applied to

a

control voltage. The control voltage changes the output amplitude of the oscillator, and hence corrects for the change in the -2700 volt

supply. 4-50. The crt

unblanking

is

normally biased off. The positive

gate from the sweep generator, applied

to the crt control grid, overrides the bias andun-

blanks the crt.

the sweep time

The gating pulse time

so

that the crt remains onduring

is

identical to

sweep time and external horizontal operation.

4-51. INTENSITY CONTROL.

INTENSITY control R319 varies the -2700 volts

4-52. supplied to the crt control grid.

FOCUS

control R334

varies the voltage supplied to focus element of the

crt to produce control

a

sharply defined trace. Astigmatism

R340, part of the voltage divider from the +370 volt supply to the +I10 volt supply, varies the voltage on the crt to compensate for electron-beam defocusing when the beam

is

being deflected by the

vertical or horizontal signals. A section of the

BEAM F'INDER

is

in the crt control-grid supply. When pressed, the switch returns the grid supply to +370 volts instead of ground, turning on the crt.

4-53. SCALE CONTROL. 4-54. SCALE control R350 rotates the trace by vary-

ing the current through

a

coil around the neck of the

crt, and hence the magnetic field through which the

beam must pass. Rotation of the SCALE control

changes the voltage and polarity across the deflection coil enough to give

*lo

degrees.

4-55.

LOW-VOLTAGE POWER SUPPLIES.

a

control range of approximately

4-56. The low-voltage power supplies include an independent supply and three dependent supplies. The

-100 volt supply reference for the +370 and

is

the independent supply.

+llO

volt supplies and

It

is

provides operating voltage to the differential amplifier of the +110 volt supply and to the sensor ampli-

fier of the +6.3 volt supply.

a

4- 6

REGULATOR

-

OSCl LLATOR

I

V30

Figure 4-8. High-Voltage Power Supply Block Diagram

V306

I

t

-IOOV

4

H.

V.

T R A NSFO RM ER

RECTI

b

RECTIFIER

V302, V303

FI

ER

V304

DOUBLER

c:

-2700V

-

W

CATHODE

ACCELERATING

TO CRT

+9300V

TO

CRT

ELECTRODE

01526-1

Model

175A

Section

Paragraph

IV

4-57

RECTIFIER

F

I

LTER

F

I

RECTI

ER

FILTER

-i

DRIVER

a424

Q42

I

,Q422,Q423

DRIVER

Q443 Q444

REGULATOR

Q46

I

4

t

SENSOR

AMPLIFIER

Q425

at

A

SENSOR

AMPLIFIER

it

-

I

-

4

+370V

+llOV

-IOOV

RECTI FlER

FILTER

RECTIFIER

FILTER

4-57.

A

simplified block diagram of the regulated output).

is

power supplies

regulator acts each supply output (even

the return leg of the supply,

+370

volt returns, the regulator

shown in figure

as

a

variable resistance in series with output against a reference voltage. The amplifier

if

the series regulator

Figure

as

in the

is

DRIVER

DIFFERENTIAL

AMPL

I

FlER

V461

8

T

DRIVER

0402,4483

4-9.

Low-Voltage Power-Supply Block Diagram

4-9.

Each series

is

in then changes the effective resistance

+110

volt and regulator, and thereby the voltage drop across

in

series with the oppose the change in output voltage.

SENSOR

AMPLIFIER

0484

A

any change in the output voltage by comparing the

4

sensor or differential amplifier senses

w:

v

*’

A

-

BD-L-lll

b

-6.3V

b

+6.3V

of

the series

it,

to

01526-1

4-7

Section

V

Table 5-1

Model 175A

~

Item

1

Instrument

~

'ertical Response

Table 5-1. Test Equipment for Checks and Adjustments

Instrument

Required to Test Mode 1

Horizontal Bandwidth Trigger Sensitivity

Signal

Generator

~~~ ~

Characteristics

50 kc, 500 kc, 1 mc, 50mc,

1.5 volt output; output amplitude constant with frequency

Oscillator Trigger Point

Frequency:

1

kc

Amplitude: 10 volts

Calibration

Generator

Output: 0.3 to 50 volts peak-

0.2

0

to 300

volts

to peak, 0.03 to rms (*0.350/0), volts dc

Horizontal Sensitivity

Calibrator

High-Voltage Power

Supply

Sweep Gain

Trigger Sensitivity and

Symmetry

Vertical Gain

Calibrator

~~ ~

Time -Mark

Generator

Marker intervals from

0.1 psec to 5 sec in 1-2-5 steps; output am-

plitude greater than 50 mv

Sweep Calibration Sweep Magnifier Pattern Sweep Time

Vertical Bandwidth

Tester

plug-in unit

Vertical Pulse Response

Ref

Para

5-13 5-17

5-16

5-12 5-21

5-37

5

-42

5-50 5-55

5-58 5-18

5-19 5-39 5-52

5-20 5-57

Tektronix

Type 19OA

@

200CD

@738 AR

Tektronix

Type 180A

9

10405A Mercury-pulser vertical

6

Square-Wave

Generator

Test

Oscilloscope

DC Voltmeter

9

High-Voltage

Vacuum -Tube

Voltmeter

10

11

AC Voltmeter

Test Plug

12 Vertical Test

Adapter

Frequency: 4 kc to

1

mc

Output (open circuit):

600 ohm: 50 volts

75 ohm:

7

volts

10-mc passband, external

sync, 0.1 psec/cm to 5 sec/cm sweep time

Range:

0

-

4CO

0 - 3000

vdc,

1%

vdc, 8%

full scale

Input Impedance:

To

be constructed

1

megohm

(see figure 5-1)

Test plug to allow signals

to be applied directly to vertical amplifier

Intensity Modulation Horizontal-Amplifier

Frequency Compensation Sweep Length Scan Response

Sweep and Gate Output Scan Response

Low -Voltage Power

Supplies Preset

High-Voltage Power

Supply

Low

-Voltage Power

Supplies

scan Response none

Vertical Gain

5-22 5-46 5-51

5-56

5-23 5-56

5-33 5-49

5-35

5-33

5-56

'@211A

$3

160B

$3

170A

@

175A w/08*

@

412A

'@

410B

\@

459A

$3

400D/H/L Range: 1 mv to 0.1 volt

@

10404A

13 Variable

Transformer

To vary line voltage from 102 to

measurement (para 5-33)

To

hold line voltage at 115 volts for waveform and voltage measurements

during adjustment

*

Model 175A Oscilloscope with option 08, Sweep and Gate Output

-0

5

128

(204 to 256) volts for power-supply

01526-1

Model 175A

Paragraphs 5-1 to 5-12

Section

V

SECTION

MAINTENANCE

5

-1.

INTR

0

DU

CTION.

5-

2.

This section covers routine maintenance, troubleshooting, and adjustment of the Model 175A Oscilloscope.

may be used to verify proper operation of the instrument at incoming inspection or after adjustments have been made.

5-3.

SERVICING THE AIR FILTER.

5-4. Inspect the

ment and clean to restrict the flow of cooling the

filter in warm water and detergent. Dry thoroughly and coat with a from Research Products Company, Inc. This adhesive your Hewlett-Packard sales representative.

5-5.

5-6. The performance check mine whether or not the instrument in

refer

horizontal plug-in units, refer to the individual manuals covering these instruments.

5-7. TEST EQUIPMENT. 5-8. Test equipment recommended for the per-

formance check

7.

istics may 5-9. PRELIMINARY SETTINGS.

5-10. Vertical and horizontal plug-in units must be in place to make the performance check. Set the 115230 volt switch to the line voltage being used.

channel, select CHANNEL trols. Make the following settings on the panel of the vertical plug-in unit:

settings on the panel of the horizontal plug-in unit:

is

PERFORMANCE CHECK.

its

specifications. Should adjustment be required,

to paragraph 5-25.

Similar instruments having the listed character-

a.

If

the vertical plug-in unit

AC-DC..

SENSITIVITY VERNIER

b.

Depending on model number, make the following

Model 1780A: Model 1781A/B:

Model 1782A:

Model 1783A:

A

performance check

air

filter at the rear of the instru-

it

before

from the instrument and wash

filter

adhesive such

available from heating supply stores or from

is

listed in table 5-1, items 1 through

be

substituted.

it

becomes clogged enough

To check the vertical and

A

and use channel A con-

..................

..........

.................

SWEEP OCCURRENCE. SWEEP SELECTOR FUNCTION TIME MARKER

.............

..........

is

included which

air.

To clean, remove

it

as

Filter Coat No. 3

is

intended to deter-

is

operating with-

has

more than one

2

VOLTS/CM

...

MAINSWEEP

thoroughly

AC

CAL

NORMAL

OFF OFF

V

c. Make the following settings on the Model 175A:

POWER

INTENSITY MODULATION SWEEP TIME Sweep VERNIER HORIZONTAL DISPLAY EXTERNAL VERNIER

TRIGGER SOURCE

SWEEP MODE

TRIGGER LEVEL TRIGGER SLOPE

d. Depress BEAM FINDER to locate trace. With BEAM FINDER depressed, center display with horizontal and vertical position controls.

e. Release BEAM FINDER and turn INTENSITY control clockwise,

pear on screen.

f.

The INTENSITY control should vary the intensity of the display from extinguished to brighter than normal intensity. Adjust INTENSITY for normal viewing level.

g. The FOCUS control should defocus the display at each extreme of the control and focus the display at approximately midrange. Adjust FOCUS for sharpest display.

h. Adjust SCALE control to align the trace parallel

to the horizontal graticule lines.

5-11. HORIZONTAL AMPLIFIER. 5- 12. SENSITIVITY.

a. Connect the Calibration Generator to HORIZ

INPUT.

b. Set Calibration Generator output for 10 volts

peak- to-peak.

c. Set:

HORIZONTAL DISPLAY EXTERNAL VERNIER. fully counterclockwise

d. Horizontal deflection should be

e. Set:

EXTERNAL VERNIER

f.

Horizontal deflection should be 10 cm k0.5 cm.

g. Set Calibration Generator output for

peak-to-peak.

h. Set:

HORIZONTAL DISPLAY

..................

....

.........

INTERNAL

1

MSEC/CM

.............

.........

............

..........

FREE RUN

ON

CAL

X1

CAL

INT

.............

if

necessary. A trace should ap-

. .

1

VOLT/CM AC

1

cm or less.

..........

.

0.1 VOLT/CM AC

1

(+)

CAL

volt

0

01526-1

5-1

Section

Paragraphs 5-13 to 5-17

DISPLAY in the same manner.

5-13. BANDWIDTH.

amplitude for a horizontal deflection of

5-14. SWEEP GENERATOR. 5-15. PRESET.

vertical INPUT.

V

i.

Horizontal deflection should be 10 cm *0.5 cm.

j.

Check the two dc positions of HORIZONTAL

k. Disconnect Calibration Generator.

a. Connect Signal Generator to HORIZ INPUT. b. Set:

HORIZONTAL DISPLAY.

c. Set Signal Generator for 50 kc and adjust output

d. Set frequency of Signal Generator to e. Horizontal deflection should be at least 7 cm.

f.

Disconnect Signal Generator.

a. Set:

HORIZONTAL DISPLAY SWEEP MODE

b. No sweep should be present.

c.

Connect CALIBRATOR 10 VOLT output to the

d.

A

stable synchronized display should be present.

e.

Disconnect CALIBRATOR.

*

.

0.1 VOLT/CM DC

.........

*

- * -

.

10

500

PRESET

cm.

kc.

X1

Model 175A

Set Signal Generator frequency to 1 mc and out-

c.

put amplitude for

Adjust TRIGGER LEVEL,

d. synchronized display and reduce the Signal Generator output amplitude until the sweep stops. The sweep should continue to trigger at signal amplitudes 0.2 cm or greater.

e. Set:

TRIGGER SOURCE

f.

Repeat steps c and d. The sweep should con-

tinue to trigger at signal amplitudes of approximately

0.5 cm or greater. g. Set:

TRIGGER SOURCE

h. Repeat steps c and d. The sweep should con-

tinue to trigger at signal amplitudes of approximately

0.5 cm or greater.

i.

Set frequency of Signal Generator to

output amplitude for 3 cm of deflection.

j.

Set: SWEEP TIME

HORIZONTAL DISPLAY

k. Repeat step d. The sweep should continue to

trigger at signal amplitudes of approximately

or greater.

m. Set:

TRIGGER SOURCE

1

cm of vertical deflection.

if

necessary, for a

.........

0.1

.........

EXT

AC

EXTDC

50

mc and

pSEC/CM

X10

1

cm

EXT AC

5-16. TRIGGER POINT.

a.

Connect Oscillator to vertical INPUT.

b. Adjust Oscillator output for 5 cmdeflection, and

frequency to

c. Rotate TRIGGER LEVEL to bothextremes. The

starting point of the sweep should be adjustable to any

point

on

d. Set:

TRIGGER SLOPE

e. Rotate TRIGGER LEVEL to bothextremes. The

starting point of the sweep should be adjustable to any

point on the negative slope of the signal.

f.

Disconnect Oscillator. ReturnTRIGGER LEVEL

to

0

and TRIGGER SLOPE to

5-17. TRIGGER SENSITIVITY.

a. Connect Signal Generator to the verticalINPUT

and TRIG INPUT.

b. Set:

SWEEP TIME

Vertical SENSITIVITY

1

kc.

the positive slope of the signal.

.............

+.

..........

...

0.5

1

pSEC/CM

VOLT/CM

(-1

n. Repeat step d. The sweep should continue to trigger at signal amplitudes of approximately or greater.

p. Set:

TRIGGER SOURCE

q. Set Signal Generator output amplitude for 3 cm of deflection.

r.

Repeat step d. The sweep should continue to trigger at signal amplitudes of approximately or greater.

s.

Disconnect Signal Generator.

t.

Connect a Model 10003A (AC-21M) Probe to

vertical INPUT.

u. Set:

TRIGGER SOURCE

Vertical SENSITIVITY

SWEEP TIME

HORIZONTAL DISPLAY

TRIGGER LEVEL

v. Connect probe tip to power line. Donot connect

probe ground lead.

...........

....

.........

5 VOLTS/CM

5MSEC/CM

.........

.............

1

cm

INT

2

cm

LINE

X1

0

5-

2

01526-1

Model

175A

SWEEP TIME

.I

~SEC/CM

.2

FSEC/CM

.5

~SEC/CM

1

~SEC/CM

2

~SEC/CM

5

FSEC/CM

io

~SEC/CM

20

~SEC/CM

50

~SEC/CM

.I

MSEC/CM

.2

MSEC/CM

.5

MSEC/CM

Markers

10

mc

5

mc

1

psec

1

psec

1

psec

5

psec

10

psec

10

psec

50

psec

100

psec

100

psec

500

psec

Table

~~ ~

Interval

1

cycle/cm

1

cycle/cm

1

marker/2- cm

1

marker/cm

2

markers/cm

1

marker/cm

1

marker/cm

2

markers/cm

1

marker/cm

1

marker/cm

2

markers/cm

1

marker/cm

5-2.

Sweep Calibration

SWEEP TIME

1

MSEC/CM

2

MSEC/CM

5

MSEC/CM

io

MSEC/CM

20

MSEC/CM

50

MSEC/CM

.1

SEC/CM

.2

SEC/CM

.5

SEC/CM

1

SEC/CM

2

SEC/CM

5

SEC/CM

Paragraphs

Markers

1

msec

1

msec

5

msec

10

msec

10

msec

50

msec

100

msec

100

msec

500

msec

1

sec

1

sec

5

sec

Section

5-18

to

Interval

1

marker/cm

2

markers/cm

1

marker/cm

1

marker/cm

2

markers/cm

1

marker/cm

1

marker/cm

2

markers/cm

1

marker/cm

1

marker/cm

2

markers/cm

1

marker/cm

V

5-20

A

stable synchronized pattern should be obtained.

w.

x.

Disconnect probe from power line and vertical

INPUT.

5-18.

SWEEP CALIBRATION.

a.

Set: TRIGGER SOURCE.

SWEEP TIME. Sweep VERNIER SWEEP MODE

b.

It should take at least

to travel

c. Set:

d. Connect the Time-Mark Generator to vertical INPUT. Set Time-Mark Generator output and SWEEP TIME as shown in table

e.

TIVITY,

f.

to make the

cule edge. The 10-cm marker should be within

cm

5-19.

a. Set:

b. Set Time-Mark Generator output for

markers.

c. With HORIZONTAL POSITION, set one marker

to coincide with

0

1526-

10

cm.

SWEEP MODE Sweep VERNIER

Adjust TRIGGER LEVEL and vertical SENSI-

if

necessary, for a stable, usable display.

In each case adjust HORIZONTAL POSITION

first

marker coincide with theleft grati-

of

the right graticule edge.

SWEEP MAGNIFIER.

SWEEP TIME

HORIZONTAL DISPLAY

1

..........

left

graticule edge.

...........

...

fully counterclockwise

..........

125

seconds for the spot

FREE RUN

............

.............

5-2.

0.1

MSEC/CM

.........

5

SEC/CM

PRESET

100

psec

INT

CAL

i0.3

XI0

d. The next marker should be within i0.5 cm of

right graticule edge.

e. Set:

SWEEP TIME

f.

Set Time-Mark Generator output for

g. Set one cycle of the sine wave to cross the left

graticule edge.

h. Except for the

play, the corresponding point on the waveform one

cycle later should cross within graticule edge.

i.

Disconnect Time-Mark Generator.

5-20.

VERTICAL AMPLIFIER BANDWIDTH.

a. Install Vertical Response Tester in place of

vertical plug-in unit.

b. Set:

SWEEP TIME.

c. Adjust HORIZONTAL POSITION and TRIGGER

LEVEL,

d. Set Test Plug-In for a positive 5-cm pulse. e. Center trace with VERTICAL POSITION. The

10%

2

cm below and 2 cm above the main horizontal axis

of the crt.

f.

point on any vertical line of the graticule. The point should be no more than 7 mm to the right of the

10%

g. Remove Test Plug-In and replace verticalplug-

in unit.

if

necessary, for a stable display.

and

90%

points on the pulse rise time are now

Set HORIZONTAL POSITION to place the

point,

.........

first

cycle of the expanded dis-

.........

i0.5

0.1

cm

0.1

pSEC/CM

10

of

the right

pSEC/CM

mc.

10%

90%

5-3

Section V Paragraphs 5-21 to 5-32

Model 175A

5-21. CALIBRATOR.

a. Connect the Calibration Generator to vertical

INPUT and set output for 10 volts peak-to-peak.

b.

Set:

SWEEP TIME HORIZONTAL DISPLAY Vertical SENSITIVITY Vertical Sensitivity

VERNIER

c. Rotate vertical sensitivity VERNIER clockwise

for exactly 5 cm of vertical deflection.

d. Disconnect Calibration Generator and connect CALIBRATOR 10 VOLT output to vertical INPUT. Vertical deflection should be bient temperature and 95°F). Vertical deflection should be 5 cm cm

if

ambient temperature or 35°C and 55°C (32°F and 50°F or 95°F and 130°F).

5-22. INTENSITY MODULATION.

a.

Connect the 600-ohm output of the Square Wave Generator to vertical INPUT and INTENSITY MODULATION INPUT.

b. Set 600-ohm output to maximum and frequency

to 10 kc.

c. Set:

SWEEP TIME

Vertical SENSITIVITY INTENSITY MODULATION. Vertical POLARITY

d.

The top of the square wave should beintensified

with respect to the bottom.

e. Disconnect Square Wave Generator. Return

INTENSITY MODULATION to INT.

..........

2

.........

.....

..........

5

is

between 15°C and 35°C (50°F

is

between 0°C and 15°C

..........

....

1

counterclockwise

cm *0.05 cm

20 pSEC/CM

10 VOLTS/CM

.......

...........

MSEC/CM

X1

VOLT/CM

if

am-

*0.15

EXT

+UP

b. Connect the Model 10003A (AC-21M) Probe from

vertical INPUT to CALIBRATOR 10 VOLT output.

c. Loosen locknut plastic flange with respect to cable. The waveform should change from one with overshoot to one with undershoot.

d. Adjust probe for best square wave and tighten

locknut.

e. Disconnect probe from vertical INPUT and CALIBRATOR.

f.

to vertical INPUT. The vertical amplitude of the

display should be equal to that noted in step d.

g. Disconnect CALIBRATOR from vertical INPUT.

5-25. ADJUSTMENTS.

5-26. This section covers internal adjustments of the Model 175A. any adjustment, refer to paragraph 5-67 for troubleshooting procedures.

5-27. EQUIPMENT NEEDED FOR ADJUSTMENTS. 5-28. In table 5-1, items 3 through 13 are the test

instruments recommended to make the adjustments outlined in this section. Equipment with equivalent

characteristics may be substituted. The special

horizontal Test Plug shown in figure 5-1 to test the main vertical amplifier scanner outputs.

5-29. LOCATION OF ADJUSTMENTS.

5-30. and adjustments in the Model 175P.. These diagrams are screened on the inside of the top and bottom covers of the instrument.

Note vertical amplitude of display.

Connect CALIBRATOR 1 VOLT output directly

Figures 5-2 and 5-3 show the location of tubes

at

rear of probe and rotate rear

If

difficulty

is

encountered in making

is

required

5-23. SWEEP AND GATE OUTPUT

(OPTIONAL FEATURE).

a.

Set SWEEP MODE to FREE RUN.

b. Trigger Test Oscilloscope with gate output

signal from Model 175A.

c. Observe SWEEP OUTPUT signal on Test

cilloscope.

imately -2.5 to +2.5 volts on

settings.

d. Observe GATE OUTPUT signal on Test Oscilloscope. Signal should be approximately the duration of sweep on all SWEEP TIME settings.

e. Disconnect Test Oscilloscope. 5-24. ACCESSORY PROBES.

a.

Set: SWEEP TIME

Vertical SENSITIVITY

5-4

Signal should be a linear ramp of approx-

.........

all

...

0.2 VOLTS/CM

SWEEP TIME

4

0.5 MSEC/CM

Os-

volts for

5-31. PRELIMINARY SETTINGS.

5-32. Install vertical and horizontal plug-in units in their compartments in the Model 175A. If the vertical plug-in unit has more than one channel, select CHANNEL

a. Make the following settings on the panel of the

vertical plug-in unit.

AC-DC.. VERNIER

b.

Depending on model number, make the follow-

ing settings on the panel of horizontal plug-in unit:

Model 1780A:

SWEEP OCCURRENCE.

Model 1781AjB:

SWEEP SELECTOR

Model 1782A:

FUNCTION

Model 1783A:

TIME MARKER.

A

and use channel A controls.

.................

..

.NORMAL

...

MAIN SWEEP

...........

........

AC

CAL

OFF

01526-1