HP 122AR, 122A Service manual

122A

OSGlllOSCOPE

OPERATING AND SERVICING MANUAL

FOR

MODEL 122A/AR

OSCILLOSCOPE

101

SERIAL

AND ABOVE

Copyright HEWLETT-PACKARD COMPANY

275

PAGE MILL ROAD, PAL0 ALTO, CALIFORNIA,

U.

1959

S.

A.

122AQ01

SWEEP

Model 122A

SPECIFICATIONS

Sweep Range: 15 Calibrated sweeps, accurate to within

Sweep Expand:

Synchronization:

Trigger Point: Control overrides automatic ailu

VERTICAL AMPLIFIERS

Bandwidth:

Sensitivity:

*5%,

in a 1, 2,

5

psec/cm to 200 millisec/cm.

Vernier

permits continuous adjustment sweep time between calibrated steps and extends the 200 millisec/cm to at least

X5

sweep expansioil

1

psec/cm.

accuracy Automatic from

0.5

is

40%.

sec/c

lllay

Expansion

50

cps to

uc;

ust;u

is

about the

mu

ail

xaiigcs

center

KC;

internally rrom vertical deflection signals

and expands fastest sweep

of the CRT and expanded

causing 1/2 cm or more vertical deflection; from external signals peak-to-peak or greater, and from

d

+10

-10 an Dperation.

I

matic

DC

coupled: dc to AC coupled: 2 cps to Bandwidth

10

millivolts/cm to

volts. Turning fully counterclockwise into AU1

200

kc.

200

kc.

is

independent of calibrated sensitivity setting.

100

volts/cm.

line

voltage.

,,F;Illllcu

clIF;

LILRRF;l

--

4

calibrated steps accurate within

5,

10,

to be set between

-

r0

restores auto-

...

sequence,

2.5

01

steF

ta

sweep

volts

*5%,

10 mv/cm, 100 mv/cm, 1 v/cm and 10 v/cm. Vernier permits continuous

stem

adjustment of sensitivitv between

and extends 10 v/cm step to at least

100 v/cm.

Internal Calibrator:

Input Impedance:

Phase Shift:

Balanced Input:

Difference Input:

Vertical

Presentation:

Calibrating signal automatically connected to vertical amplifier for standardizing of gain, acc

1

megohm,-apprc

Vertical and hoi

*2"

to 100

10

mv/cm

On by approximate

mode signal mi Both input signals

all

on

vertical sensitivity ranges. The sensitivity switches may be set sep-

:uracy *2%.

50

)ximately

-:.--.-..-I

ilruiiLai

then verniers

kc

w

'ange on both amplifiers. Input impeda

r

ppf.

:ly 25 1st not exceed

may

ppf shunt capacitance.

---1:1:---

amuiiiiers

are

fully

L

----

nave

cw.

-----

same

Common mode rejectionis

*3

volts peak.

IJ~

swiccneu

to

one cnannei to give differential input

-L-

unase

I-

characteristics within

nce,

2 megohms shunted

40

at least

db. Common

arately to allow mixing signals of different levels. Common mode rejection

is

at

least

40

db with

on most sensitive range,

30

db on other

es

ranges.

A

Switch selects:

O~LY,

B

ONLY, B-A, ALTERNATE

or

CHOPPED.

Model 122A

-IORIZONTAL AMPLIFIER

SPECIFICATIONS (CONT’D.)

Bandwidth:

Sensitivity:

Input Impedance:

Phase Shift:

SENERAL

Cathode Ray Tube:

CRT Bezel:

CRT Plates:

DC coupled: dc AC coupled: 2 cps to 200 kc. Bandwidth

0.1 volt/cm to 100 volts/cm. v/cm, 1 v/cm, and 10 v/cm. Vernier permits continuous adjustment

.1

sensitivity between steps and extends 10 v/cm step to

1

megohm, nominal, shunted by approximately 100

Horizontal and vertical amplifiers have same phase characteristics within *2 to 100 kc.

5AQPl mono-accelerator normally supplied; 2500 volt accelerating potential. P7 and special applications.

Light proof bezel provides firm mount for oscilloscope camera and moved easily for quick change

Direct connection

approximately 20 v/cm.

P11

to

200 kc.

is

independent of calibrated sensitivity setting.

3

calibrated steps, accurate within

phosphors

are

also available. P2

of

filter.

to

deflection plates via terminals on

wf.

is

available

at

rear.

least

if

desired for

Sensitivity

.5%,

of

100 v/cm.

is

re-

Intensity Modulated:

Filter

Illuminated Graticule:

Supplied:

Dimensions:

Weight:

Power:

Accessories

Available:

Terminals on Color of

Green with Amber with P7 Blue with

Edge lighted with controlled illumination,

squares. Major horizontal and vertical axes have 2 mm subdivisions, Cabinet Mount: 9-3/4 in. wide, 15 in. high, 21-1/4 in. deep.

Rack Mount:

Cabinet Mount: Net 35 lbs., shipping 51 Ibs. Rack Mount:

115/230 volts

AC-83A Viewing

rear.

+20 v to blank

filter

compatible with CRT phosphor supplied:

P1

and P2

P11.

19 in. wide,

19-1/2 in. deep behind panel.

Net

33

lbs., shipping 48 lbs.

+lo%,

50-1000 cps; approximately 150 watts.

Hood,

face-fitting molded rubber.

trace

of normal intensity.

7

in. high, 21-1/4 in. deep.

10 cm x 10 cm, marked in cm

CONTENTS

SECTION

SECTION I1 OPERATING INSTRUCTIONS

SECTION

SECTION IV MAINTENANCE

111

I

GENERAL INFORMATION Page

1

.

1

General Description

1

.

2

Damage in Transit

1

.

3

Power Line Voltages

1

.

4

Conversion for 230 Volt

1

.

5

Accessories Available

2

.

1

Controls and Terminals

2

.

2

.

2 . 4

CIRCUIT DESCRIPTION

3

.

3 . 2 3 . 3

3

.

3 . 5

.

3 6

Vertical Amplifier Input Considerations

2

Checking Horizontal Amplifier Gair Calibration

3

Operating Drawings

1

General Content Vertical Amplification Channels Horizontal Amplification Channels

4

Sweep Generator High Voltage Power supply Low Voltage Power Supply

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

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

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

.

0

.

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

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

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

..........

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

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

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

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

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

i

.

i

.

1-1 1-1 1-1

I1 . 1

11

.

I1 . 1 I1

.

111 . 1

111

.

I11

.

111

.

111

. .

111

1 1

1

2

3

3 3

SECTION

V

4-1

4-2

4-3 4-4 4-5 4-6 4-7

4-a

4-9

4

.

4

.

4 . 12

.

4

TABLEOFREPLACEABLEPARTS

5

.

Introduction Front Panel Operational Check Removing the Cabinet

Tube Replacement.

Trouble-Shooting Procedure Condensed Test and Adjustment Procedure

Complete Adjustment Procedure Turn On Procedure

Power Supplies

Trigger Generator

10

Vertical Amplifier

11

Horizontal Amplifier Adjustments Sweep Generator

13

Table

1

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

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

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

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

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

of

Replaceable

Parts

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

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

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

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

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

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

IV

.

1

IV

.

2

IV

.

5

IV

.

5

IV

.

7

IV

.

9

IV

.

11

IV . 11

IV

.

11

IV

.

12

IV

.

13

IV

.

15

IV

.

15

V . 1

I

I I

I

I I I

I

I I

I

I I

I

CATHODE RAY TUBE WARRANTY

The cathode ray ray tubes purchased from

date

of

sale by the Hewlett-PackardCompany. Broken tubes or tubes with burned phosphor

not included in this guarantee.

Your local Hewlett-Packard representative maintains

glad to process your warranty claim for you. Please consult him.

Whenever out in full and returned with the tube. Follow shipping instructions carefullyto insure safe rival, since no credit can be allowed on broken tubes.

1)

2)

3)

4)

5)

6)

tube

supplied in your Hewlett-Packard Oscilloscope and replacement cathode

@

,

are guaranteed against electrical failure for one year from the

a

stock of replacement tubes and

a

tube

is

returned for a warranty claim, the reverse side of this sheet must

SHIPPING INSTRUCTIONS

Carefully wrap the

padding material.

Wrap the above in heavy kraft paper.

Pack in a rigid container which

the tube in each dimension.

Surround the tube withat

similar shockabsorbing material. tight

all

around the

Tubes

Ship prepaid preferably by AIR FREIGHTor RAILWAY EXPRESS.

We do not recommend parcel post or

returned from outside the continental United States should

be

packed in a wooden

tube

in

tube.

box.

1/4"

thick cotton batting or other soft

is

at least 4 inches larger than

least

four inches ofpackedexcelsior or

Be

certain that

air

parcel post shipment.

the

packing

is

be

will

filled

are

be

ar-

HEWLETT-PACKARD

co.

275

PAGE

MILL

ROAD,

PALO ALTO,

CALIF.

U.S.A.

FROM:

COMPANY:

ADDRESS:

Person to contact for further inform NAME

TITLE COMPANY: ADDRESS:

To process your claim quickly pl

1)

2)

:

@INSTRUMENT MODEL

TUBE TYPE

ease

-

CRT WARRANTY CLAIM

~~~~~~~

enter the information indic

SERIA: SERIA:

:ated

L

below:

I

DATE:

I

3)

ORIGINALTUBE

4)

YOUR PURCHASE ORDER NO

5)

DATE PURCHASED

6)

PURCHASED FROM

7)

COMPLAINT: (Please describe nature

~~~

8)

OPERATING CONDITIONS: (Please describe conditions prior to and

REPLACEMEN

of

trouble)

SIGNATURE

r

TUBE

at

time of failure

I

‘9

Model 122A Sect. I Page

1

SECTION

GENERAL INFORMATION

1-1 GENERAL DESCRIPTION 1-3 POWER LINE VOLTAGES

The Model 122A

cathode-ray oscilloscope. It has accurately brated input sensitivity and sweep-speed ranges.

This oscilloscope features dc-coupled differential

amplifiers and dual-trace operation.

Differential amplifiers the common-mode (in-phase) part

amplifying the differential (out-of-phase) part. For

instance, they plifying the desired signal. In addition, using differential amplifiers has other advantages. Normally dc amplifiers are difficult Changes such as aging and changes of potentials

cause

the common-mode type and ferential amplifiers. Thus differential amplifiers are also used

this drift. However, these changes are of

is

a dc

to

200 kc dual-trace

are

useful since they reject

of

the input

will

reject hum pick-up while am-

to

are

rejected by dif-

to

stabilize dc amplifiers.

cali-

while

keep stable.

This instrument inal 115 or operate satisfactorily over a the nominal value,

130/260 volts normally high line voltage line voltage

127 volts.

1-4 CONVERSION FOR

The instrument can be converted from 115 v

230

v operation by reconnecting the power transformer dual primary windings as follows: Remove the instrument from the cabinet by removing the two large the instrument from the cabinet by pushing on the

rear

screws

of

the chassis.

is

designed to operate from a nom-

230

volt

source.

i.e.

103-127 volts. Operationat

will

damage the instrument. If ab-

to

be certain

from the rear

The instrument

*lo%

is

suspected monitor the

it

does not exceed

230

VOLT OPERATION

of

the cabinet. Push

1

will

variation from

to

Dual-trace operation switch. at the same time. The two signals may be viewed either alternately during consecutive sweeps chopped on each sweep. Chopped operation involves switching rapidly between the both appear to be traced simultaneously. The most useful type upon the frequencies involved. Generally, chopped operation signals may difference

1-2 DAMAGE

Refer damage

This

permits observation of

of

presentation in each

is

used with low frequency signals. These

also

(B-A)

to

the warranty page in this manual

is

apparent upon receipt.

is

obtained with an electronic

two

signals

or

two

signals

case

be viewed separately or with their

displayed on the screen.

IN

TRANSIT

will

so

that

depend

if

any

Locate the next

to minals on each side ing the windings in parallel. Remove these jumpers. Connect an insulated jumper between the second and fourth terminals, connecting the windings in

series.

Schematic blow fuse with a 1.0 amp slow-blow fuse.

1-5 ACCESSORIES AVAILABLE

An AC-83 Viewing

is

This shade the ambient light conditions. It

lower

power

the power transformer. The twoouter

Refer

for

a face-fitting moulded rubber hood used

face

beam intensity setting.

supply terminal strip situated

are

jumpered together connect-

to

the Low Voltage

details. Replace the 2.0 amp slow-

Hood

is

available

of

the cathode-ray tube under high

will

Power

at

extra cost.

permit the useof

ter-

Supply

to

Sect.

11

Page

0

e

c

Y

VI

Model

122A

c

I

\\

\

I

\

I

E

c

C

2

Y

I

I II

I

122A

Sect. I1 Page

1

P

ONTROLS AND TERMINALS

2-1

briefly shows how

nt. Additional detailed information

VERTICAL AMPLIFIER INPUT :ONSIDERATIONS

exceed the common-signal voltage limit

my conditions. This limit

Note

rid.

-

c

plus peak ac).

he

attenuators are used the voltage to the

brminals may

the

attenuation as follows:

to

operate the in-

is

*3

that this

be

TABLE

is

the sum of

increased by the amount of

2-1

is

given

volts on the

all

volt-

SECTION

II

OPERATING INSTRUCTIONS

C. Other Types of Input Other types of input

balanced input with either dual or single channel operation

as

with most other types that ranges must be observed. Thus the commonsignal limit since there red input terminal and the input grid. The red terminal does not have an attenuator between it and its input grid.’ Therefore balanced input with attenuation channel without external attenuators. However, this

may be accomplished using both channels paragraph B above and Figure

is

possible

it

may only be used on the

is

*3

is

an attenuator only between the upper

are

possible. For example,

(see

Figure

of

volts. This limitation

is

not possible using only a single

2-4).

However,

input, the limitation

.01

VOLTS/CM

is

necessary

2-3).

lower

(see

Attenuator Setting Common-Signal Limi

0.01

VOLTS/CM

0.1 1

.o

10

NOTE Maximum peak input voltage limit

volts (dc plus peak ommended ways

fer

to

Figures

cerning connections.

A.

Unbalanced Input

Maximum voltage limit

B. Differential (B-A) Input (see Figure Maximum voltage limit from each line

as

in table

least

40

VOLTS/CM. ranges, functions of the controls

2-1.

db with both switches

Rejection

ac).

The following are

of

connecting the oscilloscope. Re-

2-1

to

2-4

for further details con-

(see

Figure

as

in table

Common-signal rejection

is

at least

2-2)

set

volts

*3 30

300

500

is

600

rec-

2-1.

2-3)

to

ground trations that follow.

is

at

on

10

MILLI- model. The location of the controls on the front

30

db on other panel

2-3

CHECKING HORIZONTAL AMPLIFIER GAIN CALIBRATION

The horizontal amplifier may be calibrated by comparing it with the vertical amplifier. First, calibrate the vertical amplifier as shown in Figure Set both VERT. and HORIZ. SENSITIVITY switches to

0.1

VOLTS/CM with VERNIER’S in Cal. Feed

1

an external zontal input terminals. Adjust the input amplitude for

a

10

R114,

2-4

Basic operating procedures are shown in the cabinet model but are the same for the rack mount

for exactly

OPERATING DRAWINGS

is

volt signal into the verticaland hori-

cm high pattern. Set Horiz. Gain Adj.,

10

cm of horizontal deflection.

Directions are given for the

different in the rack mount model but the

are

2-10.

illus-

the same.

Sect.

I1

Page

2

UNBALANCED INPUT

mim

A VERT SENSITIVITY

Model

I

122A

3

\

1.

CHANNELA POLARITY

pos

UP

NE6

up

YODEL

0

SCI

c'i

'P~E

L

J

Connect input to red terminals with ground

to lower terminal.

Follow same procedure for other channel.

Figure

2-2

:1

122A

Sect.

I1

Page

3

BALANCED

INPUT

/L

Connect one lead

1.

YODEL

-JI

0

SCI

L

112.

COP

to

top terminal

nel and other lead to other channel.

2.

Set VERT. PRESENTATION to B-A.

3.

Set

both

VERT.

SENSITIVlTY

(same) sensitivity desired

Figure

2-3

of

switches to

(AC

or DC range).

one chan-

Sect.

I1

Page

4

Model

122A

BALANCED INPUT

.01

VOLTS/CM SENSITIVITY ONLY

VLI*ILR

A

VERT SENSITIVITY B VERT SENSITIVITY SWEEPTIME

"EIWlLl

vLI)yDI

,

WIZ

SEM

Balanced input may CM

ranges (AC

be

used only on

or

DC) because only the upper red

the

.

OlVOLTS/

terminal has an attenuator in series between and the amplifier input grid.

To

connect proceed

1.

Disconnect ground strap. Connect input to red terminals.

2.

as

follows:

I

it

Figure

Set

3.

4.

5.

VERT. SENSITMTY

CM

(AC or DC).

Set

VERT. PRESENTATION

Set

CHANNEL

sired.

A POLARITY

Channel

B

may

ilarly. Both channels may and observed with either CHOP. presentation.

2-4

switch

to

to to polarity de-

be

connected

be

.01

VOLTS/

A.

connected

or

sim-

ALT.

Model

122A

INTERNAL SWEEP - INTERNAL SYNCHRONIZATION

Sect.

I1

Page

5

1.

Feed vertical input signal(s) into vertical input

terminal(s).

2.

Set

VERT. PRESENTATION

presentation.

3.

Adjust VERT. SENSITIVlTY

sired sensitivity.

and

DC

coupled ranges.

(Note

switch to desired

switch(es) for de-

that

there are

)

both

AC

Figure

4.

Set

slope

5.

Set

sired

6.

E

AUTOMATIC

TRIGGER

trigger point.

2-5

SYNC

switch

of

trigger

SWEEP TIME

sweep speed.

LEVEL

T(+

€€OR

is

control

or

SENS.

not desired, rotate

to

point desired.

-

sweep

-),depending upon

switch for de-

select level of

Sect.

I1

Page

6

CH

0

PP

ED

0

PER

AT1 0 N

Model

122A

.

’-

d

Usefulfor observing low frequency signals (less than approximately ternally

1.

to

avoid

Connect signal

channel

A.

2

kc). Synchronize sweep ex-

“Jitter”.

(1)

to

two

red terminals of

Figure

2.

Connect signal of channel

3.

Set VERT. PRESENTATION

4.

Connect external sync signal.

2-6

B.

(2)

to

the

two

red terminals

to

CHOP.

Model

122A

ALTERNATE SWEEP OPERATION

/

Sect.

I1

Page

7

Useful (above approximately

1.

2.

3.

for

observing higher frequency signals

2

kc).

Connect signal channel

A.

Connect signal channel

B.

to

two red terminals

to

two

red terminals

Set VERT. PRESENTATION this method speeds. Since each

of

presentation

is

individually triggered,

to

for

ALT.

fast

this presentation can be used with internal

of

Use

sweep

Figure

triggering even when the

two

signals

related in frequency. When operating in this

of

manner the intensity

reduced

if

the

traces

the traces

are

separated on the screen. This may be eliminated by adjusting the VERTICAL POSITION controls the

traces

overlap. Usually operation

involve signals related in frequency.

if

it

is

desired to maintain phase information between the necessary is

the

then possible

case,

two

signals being viewed,

to

use

external triggering. If this

use

external triggering. It

to

separate the traces without

intensity reduction.

2-7

ares

will

be

so

that

will

Also,

it

is is

Sect.

I1

Page

8

INTERNAL SWEEP - EXTERNAL SYNCHRONIZATION

B

VERT

SENSITIVIT

Model

122A

UL

RO

1.

Feed vertical input signal(s) into vertid input

terminal(

2.

Set presentation.

3.

Adjust VERT. SENSITIVITY switch(es) for desired sensitivity. (Note and low 2 cps above

put.

in low-frequency square waves.

s).

VERT.

DC

PRESENTATION switch to desired

coupled ranges.

or

to preserve

2

cps or to eliminate dc component in in-

AC

coupling may introduce excessive

I

that

there are both AC

)

Use DC

dc

level. AC couple

coupling

be-

tilt

The sum of the dc and peak ac applied to the

INPUT

4.

Feed synchronizing into external synchronizing terminals which

ac

5.

Set SYNC switch to EXT.

6.

Adjust SWEEP TIME - HOR.

desired sweep speed.

7.

If

TRIGGER LEVEL control to select level of trigger point.

terminals must not exceed

signal

coupled.

AUTOMATIC sweep

AC

-DC

switch

600

(2-1/2v p-p or more)

has

no effect.

SENS.

is

not desired, rotate

switch for

volts.

are

Figure 2-8

Model

122A

VERTICAL BALANCE ADJUSTMENT

Sect.

I1

Page

9

1.

Set

both

VERT. SENSTI'IVITYswitches to OFF. 4. Center trace with VERT.

2.

TurnbothVERT.

SENSFlWTYVERNIERsfully

5.

Turn VERNIER fully clockwise.

counter-clockwise.

6.

Adjust BAL control

3.

Set VERT. PRESENTATION switch to A. Repeat procedure for Channel B.

Figure

2-9

to

center

POS.

trace

no

control.

or spot.

Sect.

I1

Page

10

VERTICAL SENSITIVITY CALIBRATION

Model

122A

mien

A

MRT SENSITIVITY 0 VERT SENSITIVITY

1.

Set A VERT. SENSITIVITY switch position. of

2.

Set

3.

VERNIER

Set

VERT. PRESENTATION switch

to

CAL. position.

to

vEnmn

CAL.

to

A. VERNIERS

b

4.

Adjust

The vertical amplifier the engraved markings on controls

GAIN

6

cm. Repeat

are

accurate within

are

control to give a pattern height

this

in CAL.

M)

procedure for Channel

is

now

the

calibrated

VERT.

+5%

whenever

so

SENSlTIVlTY

B.

that

the

Figure 2-10

Mod€

:1

122A

Sect.

I1

Page

11

r

INTERNAL SWEEP MAGNIFICATION

/

A

VERT

WnlcR

SENSITIVITY

e

VERT

"ERllEl

SENSITIVITY

VEwm

SWEEPTIME

KRIZ SENS

1.

Make

sure

SWP.

EXP. switch in in

2.

After obtaining pattern, center the meters of pattern to

axis

vertical

with

be

HORIZ.

magnified on center

POS.

Xl

position.

two

control.

centi-

Figure 2-11

3.

Set SWP. EXP. switch to X5.

Any two cm portion of pattern may

be

viewed magnified five times by adjustment

HORIZ.

POS.

control.

be

selected

to

of

Sect.

I1

Page

12 Model 122A

EXTERNAL HORIZONTAL INPUT

7'

1. Feed horizontal

signal

to horizontal input ter-

CHANNELA POLARITY

VERT PRESENTATION

3.

TRIGGER LEVEL

Set

SWEEP

minds. desired sensitivity.

2.

Set

AC-DC

switch for type of input coupling

This type of input will

desired. Lissajous patterns, etc.

Figure

2-12

TIME

RO

-

HOlUZ.

be

SENS.

switch for

found useful for viewing

'1

122A

HORIZONTAL

INTENSITY MODULATION OPERATION

dYICAL

D3

Sect.

I1

Page

13

03

L

REAR

T

VIEW

OF INSTRUMENT.

POSITIVE DEFLECTS UP

I

!

LDY-174

I

AUTION - The deflection plates of the oscil- To intensity modulate with an external signal:

Iscope operate

URN

THE INSTRUMENT OFF BEFORE RE-

at

a

dc potential above ground.

OVING THE COVER PLATE FROM THEDE-

Remove the vertical jumper marked

2.

Connect the external intensity modulation

Z-axis.

1.

LECTION PLATE TERMINALS, TO AVOID signal to these terminals (a negative signal OMING

IN

CONTACT WITH

HIGH

VOLTAGES.

will

brighten the trace).

Figure

2-13

Sect.

I1

Page

14

Model

122A

/

I

./.----

TOP

-.

OF

CASE

-.--

CONNECTION

HOR/Z.

/wur

-

REAR VIEW OF INSTRUMENT.

TO

DEFLECTION

VERT

iwur

PLATES

-.-.-.

LO-M-169

-.

'\.

\

i

RO

CAUTION

To connect an external signal to the deflection plates:

-

Deflection plates of cathode-ray tube operate BEFORE REMOVING COVER PLATE FROM DEFLECTION PLATE TERMINALS.

I

A.

AC COUPLED

1.

Remove the jumpers going to terminals D1 and D2 for horizontal input and/or D3 and

D4 for

2. Connect

of

3. Connect the to terminals D3 and

put blocking condensers to D3 and D4.

The POSlTION controls on the 122A trol the pattern and good focus

vertical

1

megohm 1/2

the jumpers removed in step

input.

vertical

watt

input

D4

resistors in place

blocking

and

the

will

1. condensers

horizontal in-

will

still

con-

be maintained.

Figure

at

high dc potentials. TURN 122~ OFF

B. DIRECT COUPLED

1.

Remove the jumpers going to terminals D1 and D2 for horizontal input and/or D3 and D4 for vertical input.

2. Connect leads from the vertical input directly to D3 and D4 and the lead from the horizontal input directly to D1 and D2.

POSITION controls Position voltages source. Best picture focus

plates are at +275V with respect to

2-14

will

no longer control pattern.

must

be furnished

is

obtained when

122A

by

the signal

chassis.

Model 122A Sect.

I1

Page 15

ALIGNING

SCOPE TRACE

WITH

GRATICULE

To align oscilloscope trace with graticule,

move oscilloscope from cabinet; then

1.

Loosen locking clamp with screwdriver.

2.

Adjust fiber lever to adjust position

ray

tube

in

both

radial

and longitudinal direc-

of

cathode-

re-

tions. CAUTION HIGH VOLTAGE. TAKE CARE NOT TO TOUCH TERMINALS WHICH HAVE A HIGH POTENTIAL ON THEM.

When the cathode-ray tube is tighten locking clamp and replace instrument

in cabinet.

Figure 2-15

in

desired position

Sect.

I1

Page

16

CONNECTING EXTERNAL CAPACITORS TO EXTEND SWEEP TIME

Model

122A

4

CAPACITORS

-SIDE OF FRONTPANEL

-

TOP OF

rhe slowest calibrated sweep provided strument vith the SWEEP TIME VERNIER to af least ;econd/cm or 5 seconds for the

f

you wish a slower sweep the range can be exended indefinitely apacitors to the sweep circuits.

'0

'abinet.

. .

Connect external capacitor from point shown

to ground.

is

1/5

second/cm. This can

by

connecting a pair of external

extend the sweep time, remove chassis from

Connect external capacitor across capacitor shown on SWEEP TIME/CM switch.

FRONT

full

10

IN

PANEL IN RACK-MOUNT MODEL

on

the in-

be

extended

cm sweep.

CABINET

1/2

C A PAC1

MODEL

Values of both capacitors are the same and

be determined by the sweep speed desired. that the only ranges that these capacitors affect are the

ranges. proportion to the amount of capacity added to the circuit. calibration

.5,

1,

and 2 seconds/cm respectively.

The capacitor mentioned must be a high-quality type such

loss of sweep linearity occurs these specifications

tor

is

connected to the hold-off circuits and does

not require special characteristics.

50,

100

and

200

MICROSECONDS/CM

The extension of the sieep time

Using

2

pfd capacitors

of

the above ranges to approximately

in

is

used. The second capaci-

will

step 1 of this figure

as

if

a

capacitor with

TORS

a0

Note

is

increase the

mylar.

wil:

will

in

No

Figure

2-16

Ma

del

122A

Sect.

111

Page

1

D

GENERAL CONTENT

3

-1

Thj

is

section contains a description

of

the Model 122A Oscilloscope. The material in

this

3

section

!

Vertical Amplification Channels

3-2

i

Horizontal Amplification Channel

3-3

.

Sweep Generator

3-4

I

High Voltage

3-5

I

Low Voltage Power Supply

3-0

I

3-1

Bot

.h channels

wil:

1

be given. The vertical amplifier receives

the

input signal, amplifies

def:

lection plates. It provides attenuation

inpi

ut signal, determines the vertical position

the

spot on the screen, and supplies a signal

intc

xnal synchronization. The signal comes into

the

input terminals and

the VERT. SENSITIVITY switch. If the switch

of

1

is

<

3n an AC range the signal goes through a capa-

citc

)r.

s

directly

goe

:e

thrc

str;

light-through range, an

inpi

it grid

CAI

L.

position the calibrator output

the

vertical

nected

con neo

n-lamp relaxation oscillator.

Ver

.tical Amplifiers

-

!

vertical amplifiers consist

The cha

nnels of amplification, witching multivibrator, and

a

s\

:h vertical amplifier

Eac

pled differential amplifiers in cascade. The

cou: inpi

it

amplifier in each channel has the BAL. control

ween

is

as

follows:

Power

VERTICAL AMPLIFICATION CHANNELS

are

similar

If the switch

to

the attenuator.

frequency - compensated attenuators,

is

shorted, and a CAL. range. In the

amplifier input and plate voltage

to

the calibrator. The calibrator

its

cathodes. The VERT. SENSITIVITY

Supply

so

it,

anddrives the vertical

is

fed tothe AC-DC section

is

on

a

OFF

a

is

composed of three dc-

of

the operation

only one description

Dc

range the signal

The attenuator has

range where the

is

connected to

of

two identical

switching amplifier,

a

trigger amplifier.

SECTION

C

I

R

C

U

IT

DES

VERNIER and the GAIN control plates

and output amplifier in each channel have plate-to-

grid neutralization. The VERTICAL POSITION control plifiers. the switching amplifiers since the cathode current

for

ing amplifiers. The switching amplifiers in turn

are

The VERT. PRESENTATION switch

type

A

The locked state

ENTATION switch

of

the

for

is

that the multivibrator can be locked in either of

of

two

The other channel in each

the B-A position Channel B

ALT.

The bi-stable

ENTATION switch

a

stable in either

when operating in the ALT. position, Channel

off

received from the sweep. Then Channel

is

on and Channel B

a

repetitive and occurs at the end of each sweep.

CHOP

In the CHOP. position the multivibrator

The circuit

at

position, the tween the

B-A

-

In the B-A position the signal fromchannel B input

is

of

the input amplifier. The secondamplifier

is

between the cathodes of the second am-

The output amplifiers

the output amplifiers

controlled by the switching multivibrator.

of

vertical amplifier operation as

or

B

is

possible states (Channel A on or Channel B on).

state

of

and Channel

an approximately

two

fed directly into the channel B amplifier. The

B

is

a

free-running multivibrator running

trace

channels

is

furnished by the switch-

used

when theVERT. PRES-

is

set

to

case

is

used when the VERT. PRES-

is

set to ALT. Bi-stable means

two positions.

is

on until a trigger pulse

is

turned off. This action

40

kc

rate.

is

switched back and forth be-

at a 40

C

R

I

PTI

are

between the

are

controlled by

selects

A, B or B-A.

is

biasedoff. In

locked on.

For

A

is

Thus, in the CHOP.

kc

rate.

Ill

0

N

the

follows:

Note

example,

A

is

turned

is

astable.

Sect.

III

Page 2

Model 122A

CHANNEL

A

e+

f

CHANNEL

B

OFF

0

ATTENUATOR

CALIBRATOR

ATT E N U ATOR

Figure

4)

I

(DIFFERENTIAL)

3-1.

(40KC)

8-A

Model 122A Block Diagram

DIFFERENTIAL

AMPLIFIER

3

STAGE

DIFFER ENTIA

AMPLlFl ER

I

L

-

--

I

I I

A

input

is

signal from Channel side of the Channel output

of

the Channel B amplifier

B

differential amplifier. The

ference between the Channel B and Channel signal. This

3-3

HORIZONTAL AMPLIFICATION CHANNELS

is

the only signal shown on the screen.

The horizontal amplifier receives an input either from the horizontal input terminals

fedintothe opposite

is

then the dif-

A

signal

or

from the internal sweep generator, amplifies the signal, and drives the horizontal deflection plates. horizontal amplification channel tenuation

of

the input signal, magnification of the

also

provides

The

at-

internal sweep, and determines the horizontal position of the

The signal comes into the input terminals and fed

to

AC position the signal goeb through If this switch

trace

on the screen.

the AC-DC switch..

is

in the

DC

is

If

this switch

is

a

capacitor.

in the

position the signal goes straight through. The horizontal input signal then goes through the horizontal sensitivity section the SWEEP TIME - HORIZ. SENS. switch.

of

This

switch has a three-position frequency compensated attenuator.

A

signal

is

fed

into the horizontal amplifier. This

signal may be either the horizontal input signal or

a

sawtooth signal from the sweep generator. The

position of the SWEEP TIME-HORIZ. SENS. switch

will

determine which signal

fier.

The amplifier consists

is

fed into the ampli-

of

two

differential

amplifiers in cascade. Plate-to-grid neutralization

is

used in both stages. The input differential amplifier, grid

of

POS.

VlOlA,

is

driven single-ended. The

the undriven tube, VlOlB, goes to the HORIZ.

potentiometer.

Two

potentiometers, HORIZ. SENS. VERNIER and Horiz. Gain, in the cathode circuit of potentiometers SWEEP TIME-HORIZ. SENS. switch HORIZ. SENS. ranges. the SWEEP EXPAND switch

X1

or the X5 resistor legs may tween the cathodes tiometer and between the plates other differential amplifier, V102. V102

goes

VlOl

provide gain adjustment. These

are

in the

circuit

only when the

is

in the

In the SWEEPTlME ranges

is

used. 'Either the

be

switched be-

of

V101. A

a

Phase. Adj. condenser

of

V101.

Horiz.

Tube

Bal. poten-

are

connected

VlOl

The

feeds

output of

to the horizontal deflection plates.

an-