HP 202A Service manual

SPECIFICATIONS

r

FREQUENCY RANGE:

DIAL ACCURACY:

FREQUENCY STABILITY:

OUTPUT WAVEFORMS: Sinusoidal, square, and triangular. Selected by panel switch.

MAXIMUM OUTPUT VOLTAGE:

FREQUENCY RESPONSE:

lNTE RNAL IMPEDANCE

DISTORTION:

0.008 to 1200 cps in five decade ranges with wide overlap at each dial extreme.

Within

*lo%.

At least 30 volts peak-to-peak across rated load (4000 ohms) for three waveforms. (10.6 volts RMS for sinewave.

Constant within and load.

Approximately 40 ohms over the entire range.

:

Less than 1% on

*2% from "1. 2" to "121q on dial; *3% from ". 8" to "1.2".

4%

including warm-up drift and line voltage variations of

)

*0.2 db over entire frequency range at rated output

all

ranges except X100. Less than 2% rms on

all

X100.

OUTPUT SYSTEM:

HUM LEVEL:

SYNC PULSE

POWER: Operates from

DINENSIONS: Cabinet Mount: 20-314" wide, 12-112" high, 14-112" deep.

WEIGHT: Cabinet Mount: 48 lbs; shipping weight, approximately 84 lbs.

ACCESSORIES AVAILABLE:

Can

be

operated either balanced or single-ended. Output system

is

direct-coupled; dc level of output voltage remains stable over

long periods of time. DC adjustment available on front panel.

Less than

10 volts peak negative, less than 5 microseconds duration. Sync

:

pulse occurs at crest of on other waveforms.

17 5 watts.

Rack Mount:

Rack Mount: For rack mount style: End Frames with handles for bench use.

Specify

0.05%

@No. 17 End Frames.

at

rated output.

sinewave and with corresponding positions

ll51230V

19" wide,

36 lbs; shipping weight, approximately 74 lbs.

-+lo%,

10-l/21qhigh, 14-11 4" deep.

5011000 cycles source. Requires

CONTENTS

SECTION I GENERAL DESCRIPTION Page

SECTION

II

m

1 . 1

OPERATING INSTRUCTIONS 2

.

2

.

2 . 3 230-Volt Operation 2

.

2 . 5

.

2

.

2

THEORY OF OPERATION 3

-1

3 . 2 Bi-Stable Circuit 3 . 3 Linear Integrator 3

.

3 . 5 3

.

3-7 Powersupply

General

1 Inspection

2 Controls and Terminals .

4

Operation ..........

Single-Ended Output

6

Balanced Output

7

Sync Out 11-2

General

4

Sine Synthesizer and Function Selector Switch

Output System

6

Sync Pulse Output

...........

..........

.........

.

..........

...........

.........

1-1

II . 1

II

.

11

II II II

III III

III

III III

III

. .

.

......

.

\

.

........

.

........

1 1 1

2 2

SECTION IV MAINTENANCE

General Power Supply

Function Generator (bi-stable circuit and integrator) .

Sine Synthesizer and Function Selector Output Amplifier sync Out Tube Replacement Tube Replacement Chart Power Supply Regulator Adjustment Theory of DC Balance and Distortion Adjustments

DC Balance and Distortion Adjustments . . .

Adjust Squarewave Amplitude .

Frequency Ratio and Calibration Procedure . . IV-8

Replacement of R58 Potentiometer .

SECTION

V

TABLE OF REPLACEABLE PARTS

5

.

1

Table

...........

.........

. IV

........

.......... IV

........

.

of

Replaceable

Parts

.

IV-1 IV

.

1

IV

.

2

.

2

IV

.

3

.

3 IV . 3 IV

.

4

N

.

4

IV

.

5

lV

.

5

IV

.

8

IV

.

9

V

.

1

Sect. I Page 1

1-1

GENERAL

The Model 202A Low Frequency Function Generator

is

a compact, convenient, and versatile source of transient-free test voltages between 1200 and cycles per second. It

purpose low frequency testing application and particularly valuable in the testing

geophysical equipment, vibration and stability characteristics of mechanical systems, electro-medical

equipment, and for the electrical simulation of

mechanical phenomena. Three types of output wave-

form are available; sine, square andtriangular. Also, a sync output pulse

The Model 202A Low Frequency Function Generator contains a type of relaxation oscillator that ticularly advantageous for the generation of very low

frequencies. Both a triangular and

voltage function of time are inherent in the oscillating system. Also, a by synthesis from the triangular wave.

Output amplitude and distortion are virtually in-

dependent of the frequency of operation. This type

is

useful for any general

of

servo systems,

is

available for external use.

sinewave function

a

squarewave

is

.008

is

par-

produced

SECTION

GENERAL DESCRIPTION

of oscillating system in plitude device so that no A.

sociated delay in stabilization after frequency changes,

is

required

The frequency range from

second

is

The output system

system designed for either single ended or balanced output. It has good stability with respect to current in the output and very low hum level. Both the FUNCTION

control are so arranged that the characteristics of the amplifier are independent of their position. The

internal impedance of the output amplifier

imately 40 ohms, and the unit at least 30 volts peak-to-peak to a 4000 ohm load.

A negative peak sync pulse of 10 volts into a 2500 ohm load than sinewave and at corresponding positions with the other functions.

is

covered in 5 bands. The frequency dial

linear.

selectro switch and the AMPLlTUDE

is

also provided.

5

microseconds and occurs at the crest of the

inherent^^

V.

.008 to 1200 cycles per

is

a direct-coupled amplifier

It

a constant am-

C. system, with as-

is

approx-

is

rated to deliver

has

a duration of less

direct

I

Sect.

I1

Page 1

2-1 INSPECTION

After the instrument

should be carefully inspected for damage received

If

in transit.

the procedure outlined in the "Claim for Damage in

Shipment" page at the back of the instruction book.

2-2

CONTROLS AND TERMINALS

any shipping damage

is

unpacked, the instrument

is

found, follow

RANGE

This switch range to be covered

FUNCTION This switch types of output waveform.

FREQUENCY This dial

for the

knob just below the dial escutcheon

nected to the frequency varying element. The lower

knob

is

of the frequency.

AMPLITUDE

This control adjusts the amplitude voltage admitted output

0 to 100 in arbitrary units.

from

is

used to select the desired frequency

by

the frequency dial.

is

used to select any one of the three

is

calibrated directly in cycles per second

X1 frequency range of the oscillator. The

is

directly con-

a

mechanical vernier for fine adjustment

of

the oscillator

to

the amplifier and, therefore,

of

.the instrument. This control

is

calibrated

the

SECTION

II

OPERATING INSTRUCTIONS

OUTPUT This group consists of three terminals. The one marked "G" chassis. are the OUTPUT terminals. With respect to the ground terminal each of these outputs has equal magnitude of signal, but they are 180" out of phase with each other. The internal impedance between the two OUTPUT

SYNC OUT

The Sync Out terminals are single-ended and have

an internal impedance of about 2,000 ohms.

Power Cable

The three-conductor power cable a three-prong plug. The third prong off -set pin which provides adapter may be obtained to permit use of this plug with two-conductor receptacles.

2-3 230-VOLT OPERATION

This instrument the power transformer primaries connected in parallel for

on

ified primaries will have to be connected in series shown in "Transformer Details" on the schematic wiring diagram

is

connected directly to the instrument

The

other two terminals, vertically aligned,

115

v operation, unless otherwise spec-

the order.

terminals

is

If

of

the Power Supply Section.

is

appmximately

is

supplied with

a

chassis ground. An

shipped from the factory with

230 v operation

is

40

ohms.

is

a round

desired,

the

as

POWER This toggle switch controls the power supplied to

the instrument from the power line.

FUSE

The fuseholder, which tains the power line fuse. Refer to the Table

Replaceable

Parts

is

located on the panel, con-

for the correct fuse rating.

of

2-4 OPERATION

The following step-by-step procedure should used

as

a

guide when operating this instrument.

1) Turn the POWER switch seconds for oscillations to start. The instrument will operate nearly within specifications after

few minutes warm-up.

30

cations after

minutes.

It

to

ON. Allow thirty

will

be within specifi-

be

a

Sect.

I1

Page 2

2) Set the

desired frequency. The frequency dial scale must

be

multiplied by the RANGE switch setting to obtain the oscillator frequency. Example: 4 (on dial scale) plying factor indicated by RANGE switch setting)

=

.4 cycles/sec.

3)

Set the FUNCTION switch for the desired output

waveform.

4)

Connect the equipment under test to the OUTPUT

terminals.

5) Adjust the AMPLITUDE Control for the desired

output voltage. Because the frequency response

is

rated k0.2 db, the output amplitude may sured level will be correct (within these limits) for any other frequency.

RANGE

at

any convenient frequency and the output

and FREQUENCY controls for the

the

multiplying factor indicated by

x

.l

(multi-

be

NOTES

mea-

be

must and the strapped pair will then be the ground side of the output.

2-6

Connect the two OUTPUT binding posts ment being supplied. The then being driven. Under these conditions the internal impedance of the Model 202A from either OUTPUT terminal to ground capacitor (C29). A maximum dc voltage of 400 volts

may and the capacitor (C29). The 40 ohms internal impedance

(resistive) will shunt the impedance existing between the two signal inputs of the system being driven.

Under circumstances where the connection places the Model

rent, distortion of the Model

if

through the Model 202A output system.

connected

BALANCED

be

connected to the chassis of the equipment

be

applied between either OUTPUT terminal

"G" terminal without damaging the 1 pf

202A

greater than 10 ma peak current

to

one of the OUTPUT terminals,

OUTPUT

to

the equip-

"G" binding post may

is

7900 ohms in series with a 1 pf

in

series with a path carrying cur-

202A output will occur

is

caused to flow

When small output voltages are required it may

an

desirable to use because the hum and noise constant with output amplitude.

To

minimize distortion in the output waveform,

always use the lowest RANGE when the overlap

of

the FREQUENCY dial permits a choice.

external attenuator. This

in

the output

is

be

is

nearly

-------------

2-5

SINGLE-ENDED

The terminal

OUTPVT terminals. For single-ended operation

FYgwe

marked

2-L Single-Ended

"(3"

OUTPUT

is

isolated from the actual

0

EQUIPMENT

BEING

SUPPLIED squarewave.

-

Output

Co~ections directly connected to the chassis.

"(3'

RO

@

Figure 2-2. Balanced Output Connections

2-7

SYNC.

The SYNC. OUT

5 microseconds duration and

a

2,500 ohm load.

into and triangular crests and at the rise

respect to one of the OUTPUT terminals and at the negative crest of the other. Therefore, changed by 180" with respect by reversing connections to the two OUTPUT terminals, which are otherwise completely interchange-

able. The SYNC. OUT terminal marked

OUT

is

a negative pulse of less than

It

occurs at the positive crests with

0

EQUIPMENT

SUPPLIED

ground or no

-

at

occurs on one of the sine

to

signal point

least 10 volts peak

orfall of the

it

can

be

the output system

"G1'

is

Sect.

111

Page

1

3-1

GENERAL

Figure 3-1 depicts the general scheme of the @Model

202A

and indicates the waveforms produced. The bistable circuit consists of a flip-flop circuit capable of producing a square-wave output at point vided

it

is

triggered at the proper time. This done by including in the bi-stable circuit, a two-way comparator circuit which produces the proper triggers for the flip-flop whenever the switching signal becomes equal to either the or the "minus switching reference". The triangular switching signal returned to the bi-stable circuit

"plus switching reference"

A,

pro-

is

SECTION

Ill

THEORY OF OPERATION

is

that seen between points B and

of square wave to triangular wave takes place in the integrator unit which produce an accurate integral of the applied square

wave. The bi-stable circuit and linear integrator

are loop coupled in such a manner that the resulting

is

relaxation oscillator quency operation.

sinewave output

The the triangular voltage at point

level at point

is

fixed, and the network between C and

D.

suitable for very low fre-

is

taken from a point C between

The resistance between B and

D.

The conversion

is

carefully designed to

B

and the average

D

C

is

a

+

SWITCHING REF

+

SWITCHING SIGNAL

-SWITCHING REF

-

+

1

OUTPUT

Figure 3-1. Model

=

CR12

CRlO

CRIl

CR13

202A

-

8+

Function Generator

0

@

AVE

FtfH

,

-

OUTPUT

AMPLIFIER

vOLT4GE FROM

@TO

@

VOLTAGE FROM

, ,

Sect.

III

Page

2

non-linear system which synthesizes a

sinewave from the triangular wave. This network consists of a group of biased diodes arranged in such a manner that at certain predetermined voltage levels they begin to conduct, therefore, providing shunt paths

D.

from C to

Each additional shunt path reduces

the slope of the triangle in the proper amount so

that the wave This approximation

which a

is

shaped to approximate a sinewave.

is

as shown, and the degree to

sinewave may be approached depends on the number of diodes. Thus there are available the

sinewave C, triangular wave B, and squarewave A functions with respect to D to be selected and brought to the OUTPUT terminals through the output amplifier. The output amplifier has a differ-

ential input and push-pull output.

3-2

BI-STABLE CIRCUIT

Figure 3-2 shows the details of the bi-stable circuit and includes the integrator in block form in order to indicate the bilateral connection from integrator output to comparator input.

The portion of the diagram composed of

V1, V2 and V3 is the "bi-stable circuit". Actually, this circuit citors

is

to cathode of

is

a combination of two circuits.

If

capa-

C10 and C13 are disconnected so that there

no possibility of inductive coupling from grids

V1 and V2, the remaining circuit

is

the well-known "flip-flop" or Eccles-Jordan trigger circuit. The other circuit which appears in the bi-

is

stable circuit

"Multiar". The multiar

a voltage comparator known as the

is

a circuit which employs

a regenerative loop to produce a pulse when the

of

two input voltages are equal. There are two

is

in the bi-stable unit. One multiar

V3A and T2, and the other of V2, 3B and T1.

V1,

composed of

these

The cathode of V3A and the plate of V3B are connected to reference voltages derived from the voltage regulator tubes V5 and V6. The triangular.

is

wave of

applied

V3B. As the voltage on the plate of V3A rises

towards the plus switching reference,

to

the plate of V3A and the cathode

V1

is

con-

ducting, but when V3A conducts, a negative pulse

is

formed on the grid of V1 which flips the Bi-Stable Unit to its other stable state and starts the voltage on the cathode of V3B towards the minus switching

Bf

-

$

4

I

SEC13

-

~'j1133!

V3B

IE

+REF

T

+

-

-REF

-

T

-

.-.

*

LINEAR

INTEGRATOR

R20

.0-"-,,

*

B-

Figure

3-2.

Details

of

Bi-Stable Circuit

and

Switching System

reference. When V3B conducts the Bi-Stable Unit

is

flipped back to its original state, completing one

cycle of operation. Voltage regulator tubes V5 and V6 are connected

by a voltage divider from which the switching reference voltages are taken. They also provide the limiting voltages applied to tubes

V7 and V8 which are seen to be a push-pull clamping system. Inasmuch as the integrator output

is

to the input, it

seen that the magnitude of square-

is

directly related

wave applied must be carefully controlled. Although only the squarewave appearing at the plate of Vl

is

needed to drive the integrator, the clamp

is

made push-pull to prevent excessive current variations in the regulator tubes. The action of V7B and V8B

is

such that if the applied waveform

has peak excursions in excess of the potentials on

the remaining cathode and plate, these being deter-

by

mined

regulator tubes V5 and V6, a current will flow through R20 which drops the voltage to very nearly the potential of the regulated element of the conducting section of the diode. The action of the

is

other diodes

the same, but 180" out of phase,

inasmuch as they are coupled to the plate of V2.

In

this way, waveforms appearing on the clamped sides of R21 and magnitude as well as the average of dc level of the squarewave

R20 are assured to be of equal

180" out of phase, and further

is

ac-

curately controlled.

3-3

LINEAR INTEGRATOR

Consider the block diagram of the linear of feedback integrator as shown in Figure 3-3. Starting with the output voltage of the amplifier at the junction of R and

be

small. For a fixed output Eo as the gain

E,,

it

is

seen that

is

high, then the signal appearing

C

(the amplifier input) must

if

the gain

is

in-

creased the resultant signal at the input of the am-

plifier becomes arbitrarily small. Since the voltage

C

is

at the junction at R and

arbitrarily small, a squarewave applied to the input will cause a constant current in R. Because the current charging and dis-

charging C

is

constant, except for direction, the

voltage across C will be triangular. Since there

Sect.

III

Page 3

is

virtually no signal at the junction of R and C the

output voltage must also be triangular. In this case the frequency of the applied

signal

is

so

low that the amplifier used must be direct coupled.

is

There

a net voltage rise between input level and output level in a dc amplifier. In this particular application the average output level

is

determined as the average of the "plus reference" and "minus reference" levels, since the output excursion limited to these levels.

B

this

level does not coincide

is

with the average level of the applied squarewave,

then the positive and negative excursions of the

squarewave will not be equal,

resulting in unequal

rise and fall rates of the output triangle. Because

squarewave input

the

is

generated from the triangular

output by the bi-stable circuit, the net result is that

is

under such conditions the squarewave

really a

rectangular wave. The resulting rectangular wave

has an average value just equal to that demanded

by

of the amplifier input

virtue of the pre-set output level. The average levels of the input and output are stabilized by the use of a differential amplifier that has high gain to the difference between the voltage applied to its inputs but little or no gain to any voltage change common to both inputs.

is

Figure 3-4 shows how this

grid of the differential amplifier

is

input and

driven through R by the rectangular wave appearing on the FREQUENCY control. average voltage of this rectangular wave

done.

The right hand

V15,

is

the signal

is

The

depen-

dent on the clamping levels and the ratio of "on" to

is

"off" time. When the system on-off times (squarewave) the average

adjusted for equal

is

just the average of the clamping levels. The left hand grid has no signal because the voltage divider which in-

is

cludes the balance control

connected to the nosignal sides of the clamping tubes. However, any change in the clamping level changes the average

level appearing on both input grids in the same amount. Due to the large common cathode resistors of V15 and V16 a common mode change has very little effect. The input to the left hand grid has another function.

If

the balance control R60,

is

varied slightly, the output of the amplifier will show

a

considerable change in average level; and therefore

-

€9,

t

-

AMP

-

Eour

a

Figure 3-3. Generalized Miller or Feedback Integrator

ID-"-5.

Sect.

III

Page

4

Figure 3-4. Simplified Linear Integrator

the average level of the output can be adjusted to exactly the voltage midway between the "reference"

This

levels.

control then serves adequately to adjust the triangular wave balance which in turn equalizes the on-off time of the squarewave.

The signals appearing at the plates of the first tube V15, are 180" out of phase and nearly equal in magnitude. These signals are also very nearly the difference between the inputs on the two grids. Since there

is

no signal on the left grid, the only signal into

is

the amplifier

is

the condition originally required. The second

is

stage

a push-pull amplifier employing the signals

that at

the

junction

of

R and C, which

from the plates of the previous stage. Again the common cathode resistance

is

very little degeneration of the push-pull input.

is

very high, but there

The gain of the system to changes common to both

is

grids appearing between the input grids

250. Finally C

the cathode

about one-half while the gain to voltages

is

something over

is

fed back to the signal grid from

of

V17A which

is

180" out of phase with

the signal input.

is

The cathode follower

used as an isolation stage between the integrator and the bi-stable circuit. This completes

oscillating loop with

its

inherent

the

production of both square and triangular functions.

3-4

The triangular wave from the linear integrator

connected TION selector switch (53) the other end of R94 connected to the sine synthesizing diodes and R93B, one half of the dual meter. The synthesized as the difference signal between points C and

SINE SYNTHESIZER AND FUNCTION

SELECT OR

to

R94.

SWITCH

In

the

SINE position

AMPLITUDE

of

the

FUNC.-

potentio-

sinewave signal appears

D,

is

to

but an error signal which appears at D with respect to

B-

also appears at C with respect to

composite signal

is

applied

to

a differential amplifier

B-.

This in the output circuit. The plus and minus switching references in the

bi-stable unit are adjusted so that the ratio of the triangular wave amplitude to the conduction voltages

the

synthesizer diodes produces

of

the

least distortion

of the sinewave. This adjustment also fixes the

is

equal

to

average voltage at C and

the average

of the plus and minus switching references.

at

The dc voltages

D, and the cathode of V4 are

adjusted to be the average of the plus and minus

switching references. Since

there

is

no change in DC level applied to the Output

as

Amplifier

the AMPLITUDE control

these

voltages are equal

is

varied.

El-STABLE

f

225

VDCREG

.

Sect.

111

Page 5

t75

VDC

REG AMPLIFIER

Figure 3-5.

Sine Synthesizer and Function Selector

(A)

TO OUTPUT

Waveform from integrator output to B-. Triangular regardless of function selector position.

(B) Waveform from@to B- with selector switch in sine

position. Note distortion especially at peaks.

w

(C) Waveform from@to B- with selector switch in sine

position. in waveform (B) above.

This

t75

VDC

REG.

is

the distortion component present

ID.I.6M

RO

Figure

(D) Waveform fromato@ (i. e.

(C)

waveforms (B) and

above. ) This

mated sinewave.

3-6.

50

IL

Waveforms

:

difference between

is

the approxi-

Sect.

111

Page 6

sinewave

The

resistance across

is

approximated by varying the shunt

R93B

is

steps determined by the

diode synthesizing network. The waveform slope,

is

at first,

just that determined by R94, R93B and

the input waveform. When the first diode conducts

is

R93

shunted by a predetermined amount, decreasing the slope. Each diode in turn decreases the slope until all the diodes are conducting and the triangular wave

has

reached

its

crest. The triangular wave starts down, the diodes stop conducting in turn until the triangular wave has reached its crest. The triangular wave

starts

down, the diodes stop conduct-

ing in turn until the triangular wave reaches the

average level. The other half-cycle is formed in the same manner, but by the diodes that are biased to shape the negative excursion.

It can

be

shown that using seven segments to approx-

imate one half cycle of the

sinewave results in ap-

proximately 11 6% rms distortion. However, variations

in the diodes limit the practical result to about

1%

rms distortion.

In

the triangular wave position of the FUNCTION

selector switch the non-linear load consisting of

is

the diode network

combination R94 and R95

for all voltage levels. It

replaced by R95 so that the

is

a simple linear divider

is

adjusted to give equal

sine and triangular wave peak magnitude.

is

squarewave

connected to the FUNCTION selector

The

switch through the divider R59 and R22 which adjusts the average voltage of the squarewave to the voltage at the cathode of V4. In the squarewave position of the selector switch, R63 parallels

R93B to adjust the amplitude of the squarewave to be equal to the amplitude of the

3-5

OUTPUT

sinewave and the triangular wave.

SYSTEM

The output system consists of three stages as shown in Figure 3-7. The first Stage V18 acting

as

a pair of separate cathode followers.

is

a dual triode

These cathode followers isolate the signal input from the output stage. Any dc unbalance at the output terminals can be corrected by varying R65.

The second stage

V19

is

a differential amplifier. The difference between the two signals at its grids appears at both plates in nearly equal magnitudes

is

and 180" out of phase. This effect

due to the large

common cathode resistance. In this stage ampli-

fication takes place and also the signal difference

E

minus F third stage V20 The signals appearing at the plates of

is

converted to push-pull voltages. The

is

another pair of cathode followers.

V19 are

Figure

3-7.

Output Amplifier System of Model

202A

Sect.

111

Page

7

R44 R41

Sync Output Circuit of Model 202A

attenuated before being applied to

Figure 3-8.

the

cathode follower grids. The small shunt capacitors on the upper sides of the dividers improve the high frequency response

of the amplifier. The voltages appearing at the cathode follower output terminals are equal in magnitude and

180" out of phase. Negative feedback

is

used to reduce distortion, lower the output impedance and improve stability. This improved stability applies not only to the signal output, but to the dc level at the output terminals.

The symbol for chassis or ground first time in the output terminal network R98, and C29. for operation has been the Thus, the chassis ground

B-

In

all other description the reference level

B-,

and in the Model 202A

line

is

completely isolated from the chassis.

is

available for whatever

is

used for the

R99

CZO

is

possible to consider

connection

is

desired.

It

the two output terminals as a transformer output

and further to balance this apparent transformer to chassis by making R98 equal to

R99. The capacitor

C29 insulates the apparent transformer secondary

from ground.

If

single-ended operation

is

desired

the ground connection can be tied to either output

terminal without affecting the amplifier.

3-6

The output sync pulse circuit

SYNC PULSE OUTPUT

is

obtained from the bi-stable

V1

and V2.

On

the minus switching reference at the plate of multiar diode V3, one positive pulse and one negative pulse appear for every cycle of operation. These pulses are coupled to the grid

FlER

REGULATOR

Figure 3-9. Model 202A Power Supply

f

375

VOLTS

REG

.-0

-

+P25

VOLTS

rs

REG

Sect.

111

Page

8

of the sync pulse amplifier, V17, through an

coupling which lowers the average voltage on the

In

grid to B-. to cut-off by the bleeder to B+. When a positive pulse appears at the grid, it momentarily turns V17 "on", thus, inducing a large voltage swing in the pulse transformer primary. The resistor and diode in the secondary remove the positive excursion,

resulting in a negative pulse at the minals.

the absence of pulses, V17

SYNC OUT

is

biased

RC

ter-

3-7

The Power Supply

tor which supplies

+

divider across the + 375 volt supply. The main

requirement on the three regulated voltages

low impedance at low frequencies. Reasonable variations in the actual voltages do not affect the output frequency or waveform.

POWER

225

volt regulated outputs are taken from a voltagc

SUPPLY

is

a full wave rectifier and regula-

+

375 volts. The + 75 volt and

is

very

Sect.

IV

Page 1

4-1

GENERAL

Most of the following analyzing and adjustment procedures require the measurement of dc voltages or

the observation of waveforms. To obtain accurate

results, use a voltmeter with an input resistance of 100 megohms or more. The @Model 410B Vacuum Tube Voltmeter

All dc voltages are measured with respect to B- and not with respect to the chassis. The B- points in the instrument are connected with

Isolate all test equipment from the main chassis or

gromd Otherwise, both

may be connected to the main chassis through the test equipment.

in output stage V20 will be shorted and the tube will

be

severely damaged.

is

recommended.

black

hook-up

CAUTION

B-

and one side

I€

this happens, one cathode resistor

of

wire.

the output

--------------

SECTION

IV

MAINTENANCE

4-2

POWER SUPPLY

After power

ments, a final check of regulated voltages should

be

made. See Power Supply Regulator Adjustments

in paragraph 4-9.

SYMPTOM

Instrkent inoperative (Indicator lamp won't light, no output volt-

age). Instrument inoperative

(Indicator lamp lights, no output voltage).

supply parts replacements or adjust-

TABLE 4-1

CAUSE AND/OR

REMEDY

Blown fuse,

Measure resistance from V21 socket (pins 2 or

55,000 ohms or

more replace

If

less than 55,000 ohms clear short circuit in filter or

regulator circuits

then replace V21.

8)

F1.

to B-.

V21.

1

Whenever pssible the instrument frequency should

be set to approximately 50 the use of a capacitor in series with the ac voltmeter or oscilloscope to eliminate the dc component.

Interaction between most of the circuits of the Model

202A makes a fairly definite procedure for trouble

shooting necessary. For example, oscillator section may easily cause considerable

voltage deviations in the output system. Therefore,

is

more desirable to divide the instrument into

it five sections as follows and consider each in turn.

4-2 Power Supply

4-3 Function Generator

Sine Synthesizer and Function Selector

4-4

4- 5 Output Amplifier

4-6 Sync Out

cycles/sec. to permit

a

fault in the

Instrument inoperative (normalvoltage (Extremely low or no voltage between Y5, pin 5 and B-).

Instrument inoperative (normal ulated) (+225V regulated, off voltage).

(+

7W regulated, off

voltage) Instrument inoperative

(No

+

75 regulated voltages, V5 ionized).

+

225 regulated

and/or V6 not

atV21).

37W reg-

Defective tubes (V22, V23).

Capacitor C6 short circuited.

Defective OA2 tube (V5).

Defective OA3 (V6).

Open circuit in R62, R84, R85, R92.

6AU5

tube

R91, or

Sect.

lV

Page 2

4-3

FUNCTION GENERATOR

(bi-stable circuit and integrator)

REPAIR ANALYSIS OF FUNCTION

A.

me

voltage, then a simple test should be made to deter-

is

mine whether the fault

bi-stable circuit.

1) Connect a high resistance dc voltmeter between B- and pin 3 of tube

Set the

2) connect the lead from the center lug of the variable resistor R58. Temporarily connect this lead to

pin 5, V6

3) After this connection cated by the voltmeter should slowly climb until

is

over 200 volts.

4) Remove the lead from the + 75 Reg. supply and connect meter indication should now drop slowly 140 volts. Disconnect the lead from V5 and return it to the original connection on R58.

5)

If

quirements, then the integrator section normally and the fault circuit. then the trouble

After all defective parts have been replaced and

the necessary adjustments made, an oscilloscope should be connected between pin 3, tube

B- to see on all ranges.

No output voltage (Power Supply Section normal, no triangle voltage between on any range).

Same symptoms as above on one or more ranges.

RANa switch to the

(+

it

to pin 2, V5 (+225 regulated). The volt-

the instrument meets the above voltage re-

If

the instrument does not pass the test,

if

a good triangular waveform

SYMPTOM

V17, pin 3 and B-

This test

75 Reg.

is

in the integrator.

in the integrator or the

is

V17.

X.

).

is

made, the voltage indi-

is

confined to the bi-stable

,

TABLE 4-2.

a

GE3lERATOR

as follows:

01 position. Dis-

to

less than

is

functioning

V17 and

is

obtained

CAUSE

Replace V3, Vl5, V16, or

replacement fails to cure the trouble, see analysis procedure following this

Check RANGE

switch contacts, components, and connections.

Check C14-C18 for excessive leakage.

AND/OR

REMEDY

V1,

V17.

If

chart.

V2,

tube

7

it

4-4

SYMPTOM

Same symptoms as

above when frequency

is

dial frequency end.

Triangle not linear.

SINE SYNTHESIZER _AND FUNCTION

SELECTOR

When the trouble has been corrected in the Sine Synthesizer and Function Selector, the following checks should

is

ment

1) Sine Wave V18 and B- with oscillator set to 50 the AMPLITUDE control at maximum. Set the

FUNCTION switch in the SINE position. The waveform should imately 30 volts peak-to-peak. See Figure 3-6B.

Observe the waveform between pin 7, V18 and Bwith the same conditions as above. The waveform should be similar to Figure 3-6C and approximately 1 volt peak-to-peak.

2) Triangular Wave tween Pin 2, V18 and B- with the oscillator set

50 cycles/sec. and the AMPLITUDE control at

imum Set position. The waveform should be triangular and approximately 30 volts peak-to-peak.

Observe same conditions as above. The waveform should be triangular and approximately

3) Square Wave pin 7, V18 and sec. and the AMPLITUDE control Set the FUNCTION switch to the SQUARE position. The waveform should be square and approximately 30 volts peak-to-peak.

The

be adjustable to zero under any operating conditions by means of R65.

again functioning correctly.

the

dc voltage across the

TABLE 4-2. (CONT'D)

CAUSE

Try replacement tubes for V15, V16,

set near low

be

made to determine

-

Observe the waveform between pin 2,

be

substantially sinusoidal and approx-

-

the

FUNCTION switch in the TRIANGULAR

waveform between pin 7, V18 and

-

Observe the waveform between

B-

with the oscillator set to

and/or

Replace tubes V15,

V16, V17. Check

-

DC Balance.

Observe the waveform be-

1

volt peak-to-peak.

AND/OR

REMEDY

V17.

if

cycles/sec. and

at

OUTPUT

terminals should

the instru-

to

max-

B-

with

50

cycles1

maximum.

Sect.

IV

Rage 3

TABLE 4-3.

SYMPTOMS

Sinewave badly distorted.

DC component at OUTPUT terminals independent of AMPLITUDE control setting or varied by AMPLITUDE control.

4-5 OUTPUT AMPLIFIER

TABLE 4-4.

SYMPTOMS

CAUSE AND/OR

REMEDY

Maladjustment of R49, R51, and

R6O or defective diodes CR2 through

CR13.

Maladjustment of R65, R54, and R118 or defective tubes V4, V18,

V19, V20. See DC Balance Adjustment.

CAUSE AND/OR

REMEDY

After adjustment or tube replacement, the amplifier

.I

should meet the following specifications:

---

The output voltage should not drop more than

2%

when a 4000 ohm load

is

connected to the

output.

---

The distortion should remain within specifi-

is

cations when the output

loaded with 4000 ohms

or higher.

---

The peak-to-peak output voltage should be at least 30 volts (10. 6 volts rms with a sinewave)

is

when the output

loaded with 4000 ohms or

higher.

4-6

SYNC OUT

Specifications call for a negative sync pulse of 10 volts peak with a duration less than 5 microseconds.

The sync pulse occurs at the

>

sinewave crest and

at corresponding positions on other waveforms.

Increased distortion

when amplifier

is

loaded with 4000 ohms.

DC voltage component exists across the OUT-

PUT terminals.

Distortion increases appreciably with reduced AMPLITUDE control setting.

Failure to deliver 10

volts rms

sinewave

output.

Hum in output voltage.

Replace

V20.

Vl8, Vl9,

If

distortion

remains, turn off

the power and mea-

sure resistance be-

tween internal

chassis and main chassis. See paragraph 4-9.

See paragraph 4-4.

Replace variable resistor

R93A,

R9 3B.

Adjust regulated

&

voltage. See para-

graph 4-9. Replace

Vl8, Vl9,

v20. Excessive hum from

power

supply See

paragraph 4-9.

TABLE 4-5.

CAUSE AND/OR

SYMPTOMS

No sync pulse (Check

REMEDY

Replace

Vl7. for negative pulse with oscilloscope and with Mode1 202A set for highest frequency).

Large overshoot.

,

4-7

TUBE REPLACEMENT

Replace CR1.

Any tube with standard JETEC characteristics can be used for replacement purposes.

Whenever a tube

strument which might be affected must be tested and

is

replaced, that part of the in-

by

the change

if

necessary, adjusted to be

within specifications. See paragraph 4-8, Tube

Replacement Chart.

Sect.

lV

Page 4

4-8

TUBE REPLACEMENT CHART

TABLE 4-6. TUBE Vl, V2

V3

V4

V5, V6

V7, V8

Vl6, V17

V15,

Vl8, Vl9, V20

EFFECT

None. Variations in bottoming voltage eliminated by clamps and V8.

Frequency shift and distortion increase due to contact potential variations.

DC output level shift, probably as a function of amplitude control setting.

Possible change in frequency, distortion, or dc balance from change in regulated voltages.

Same effect as change in V3 possible, but to much less degree.

Frequency change and unbalance of triangle.

Change in dc output component,

independent of AMPLITUDE control setting.

V7

READJUSTMENT

None.

Min. Distortion and Correct

Freq. Adj.

DC Bal. Adj.

Power Supply.

Bal Adjust.

DC Minimum Distortion and

Correct Freq. Adjust.

Min. Distortion and Correct

Freq. Adj.

Min. Distortion and Correct

Freq. Adj.

Set dc output component to zero by R65, with amplitude control min.

V21 V22, V23, V24, V25

4-9

POWER SUPPLY REGULATOR ADJUSTMENT

Resistance measured between inner and outer chassis should be at least two minals disconnected from panel ground or a load.

This resistance check should be

the following adjustment procedure:

1) Connect the shorting strap between the lower output terminal and chassis ground. Connect the dc voltmeter between

voltmeter must not be grounded and the common terminal should

megohms with OUTPUT ter-

B-

and the inner chassis. The

be

connected to

No effect

Possible change in

+

225 regulated voltages.

made

before starting

B-.

None.

+

375 and

2) Connect the 202A The voltmeter indication should be between

+

230 volts with line voltage set to 115 volts.

and

3) Measure the regulated output voltage between

B-

and pin 2 of

a voltage of

4)

Measure the voltage between pin 5 of tube V5 and

B-.

This voltage should be about + 375 volts. Variations in OA3 tubes can cause this voltage low

as

+

365 or as high

Carry out procedure under

"Power Supply Regulator

Adjustment". Paragraph

4-9.

to

the power line and turn on.

tube

V5. Adjust control R11 to give

225 volts.

as

393.

to

/

be

+

.

190

as

Sect.

IV

Page

5

5) Measure the voltage between pin 5 of tube V6

B-.

and Variations in OA3 tubes can cause this voltage to fall at any point between 68 and 85 volts.

6) Repeat step 3 The characteristics of cold-cathode regulator tubes drift during about the This drift can affect the 202A output. A 72 hour

aging V5 or V6.

7) Test the regulated output voltage at pin 5 of tube

V5 while varying line voltage between 103 and 127 volts. The regulated voltage

by more than

components if the change

4-10 THEORY OF DC BALANCE AND

The output AMPLITUDE control input to the output amplifier.

at the output terminals of the AMPLITUDE control the dc levels at the ends

of

the AMPLITUDE control must be the same and

also equal to the average level of the input wave.

From the schematic wiring diagram,

the common connection between the two sections of the control level of this point by R54. The signal impedance of this point low compared with the magnitude of the AMPLITUDE control impedance, and therefore, the cathode of

has

V4 When R49, R51, R54, and R60 are adjusted properly,

there the AMPLITUDE control.

When the FUNCTION switch position, there the AMPLITUDE control, hence, the tap on that section merely carries the constant bias level set by the cathode

through a network to the clamp section of the bi-

stable circuit. R22 age level control to the same value as the cathode

The dc levels at

pendent of AMPLITUDE control setting. The dc

levels of the two output terminals may

to

be

of the signal on one grid of the second stage of the amplifier. When these adjustments are made, the dc component between the output terminals will

remain at a very low value, independent setting or waveform selected.

This voltage should be about + 7 5 volts.

if

you replace either V5 or V6.

first

72 hours of operation.

is

recommended for a new tube for either

will

normally not change

*l%.

Check power supply tubes and

is

excessive.

DISTORTION ADJUSTMENTS

is

located at the

If

the dc component

is

to be zero for all settings

it

is

connected to the cathode of V4. The

can

be adjusted to the desired value

virtually zero signal.

is

no dc component across either section

is

in the squarewave

is

no signal input to one section

of

V4. The other section

d

this network adjusts the aver-

of

the squarewave applied

is

connected

to

the amplitude

of

the

input to the amplifier are inde-

be

equal

by

R65. Control R65 varies the dc level

of

amplitude

seen that

is

very

of

V4.

adjusted

Control R49 varies the level to which the output of

a

the integrator rises in varies the level levels of the shaper diodes are not variable and therefore, the triangle input one and only one correct magnitude and average level.

Figure 4-2 shows the situation at the shaper when the two reference levels are properly adjusted.

Figure 4-2B shows the effect of having the reference levels adjusted for too large a magnitude, but with the proper average value. Figure 4-2C shows the effect of having reference levels adjusted for a triangle of the proper magnitude, but incorrect average level. This indicates between correct frequency calibration and minimum distortion. In fact, the two conditions are simultaneously satisfied by optimum settings of the same adjustments.

4-11 DC BALANCE AND DISTORTION

ADJUSTMENTS

The following test procedure re@ires a with an input resistance of at least 100 megohms such as an meter must not the meter must 202A

that

Analyzer and an Oscilloscope will also be required. A 20 minute warm-up

start

this procedure. You should also adjust the

power supply

1) Adjust the insulated 410B voltmeter to indicate

0.5 on the Use either the ECTOR switch

0.

5

setting indication will be called portion of this procedure.

2) Connect the

to the common junction of AMPLITUDE controls R93A and R93B (violet wire).

3) Connect the DC volts probe of

R93A. This

PLITUDE control.

4) Set the FUNCTION switch to TRIANGULAR and

adjust R54 for

5) Move the DC volts probe to the arm of Rl18 and

adjust R118 for an indication of approximately volts".

of

the negative excursion. The b6s

@Model 410B. In addition, the volt

be

are not at ground potential. A Distortion

as

outlined in paragraph 4-9.

1

volt range with the dc leads shorted.

"+" or the

--

with

the ZERO

COMMON

is

a

voltmeter indication of "0 volts".

positive direction and A51

to

the shaper can have

a

close relationship

dc

voltmeter

grounded as the common side of

connected to points within the

is

recommended before you

"-"

position of the SEL-

whichever one

ADJ.

"0 volts1' in the remaining

lead from the voltmeter

slate wire connected to the AM-

will

permit the

control.

to

This

the opposite end

meter

"0

-

Sect.

I'

Page 6

6) Set the imum CCW) and move the voltmeter leads to the and note the voltmeter indication (0.5 on 0-1 scale

AMPLlTUDE control to minimum (max- 15) Switch the FUNCTION selector to TRIANGULAR

is

red OUTPUT terminals. "0 volts1'). Adjust R49 to reduce the dc voltage to

of

its

7) Adjust

R65, located behind a hole in the panel

near the OUTPUT terminals, for an indication of

one-half the remaining

indicate

"0 volts1'.

initial value, then adjust R51

dc

voltage. The voltmeter should now

to

remove

"0 volts".

8) Set

of

R119, located near V1 and T2, to the middle 16) Set the FUNCTION selector to SINE and adjust

its

range.

R118 for a voltmeter indication of

"0 volts".

9) Disconnect the voltmeter and connect equipment as shown in Figure 4-1.

10) Set the FREQUENCY dial to 10, the RANGE switch to

X10 (100 cps), FUNCTION selector to

SINE, and the AMPLITUDE control for an output

of

approximately 10 volts rms.

17) Verify the distortion in the output sine wave at 100 cps,

first

on the X10 RANGE with the FREQUENCY dial at 10, then on the XlOO RANGE with the FREQUENCY dial

at

1.

I£

the distortion indications are not approximately identical, careful adjustment

of

R119 will lower the 100 cps distortion

on the XlOO RANGE.

U)

Adjust R49 and R51 to eliminate the points or

spikes at the ends of the Oscilloscope pattern. Adjustment of these controls will shift the output quenc y, you should follow the frequency shift with the Distortion Analyzer. Adjust the Distortion Analyzer sensitivity as necessary to obtain a useful pattern on the Oscilloscope.

fre-

18) Connect the voltmeter COMMON lead to the

of

common junction

AMPLITUDE controls R93A and R93B (violet wire). Connect the DC volts probe to the green wire on the opposite end of

R93B.

12) Adjust R60 for minimum distortion on the Distortion Analyzer. Repeat steps 11 and 12

is

until the distortion measured

at least 40 db below

the output voltage (1%).

as

indicated

19) Set the FUNCT ION selector to SQUARE and

the RANGE switch to meter indication

X10. Adjust R22 for a volt-

of

"0 volts1'.

13) Connect the voltmeter COMMON lead to the common junction R93B (violet wire).

14) Connect the R93B. This

DC

is

a

of

AMPLlTUDE controls R93A and

volts probe to the opposite end of

green wire connected to the AM-

20) Any dc between the red

the AMPLITUDE control

inated

by

adjusting R65 (behind the hole in the panel).

OUTPUT

at

minimum may

This voltage should vary less than

is

the AMPLITUDE control

rotated through

terminals with

kO.

PLITUDE control. range.

r

f

-hp-

MODEL 202A

LOW FREQUENCY DISTORTION OSCILLOSCOPE

FUNCTION GENERATOR ANALYZER

1

r

-hp-

MODEL 330

\

,

-hp-

MODEL 120 OR

be

elim-

5 volts when

its

full

1

130

HORIZ.@

BD-S-38

\

Figure 4-1.

Minimum Distortion and Frequency Adjustment

hstrumentation

(A) Correct setting of

reference levels.

(B)

Both

Ref. levels too large.

Sect.

IV

Page

7

(C)

+Ref. too high and -Ref. too low. Frequency correct but large 2nd harmonic as seen by peak flattening on one side and sharpening on other.

Also sine average not same as triangle.

&

Sine Ave. mental.

Figure

4-2.

Triangle

Effect of Triangle Maladjustment on Distortion and Frequency. Ten-Segment Approximations Used for Clarity.

(D)

References are correct but triangle unbalanced. Frequency correct but high second harmonic component in phase with funda-

Sect.

IV

Page 8

4-12

ADJUST SQUAREWAVE AMPLITUDE

Adjust control R63 to produce an output squarewave with the same peak-to-peak amplitude as the sine and triangular output waveforms.

4-13

The following procedure

FREQUENCY RATIO AND

CALIBRATION PROCEDURE

is

intended for use after replacement of the Range Switch or any of the frequency determining components on the Range Switch.

is

This procedure

also required following replace-

ment of frequency determining potentiometer R58.

1) Remove the cabinet or top and bottom instru-

ment covers.

2) Check that the upper and lower dial stops fall about an equal distance outside the upper and lower dial calibration marks. Correct the dial setting,

if

necessary,

by

rotating the dial on the dial mounting hub. The dial stops and not the potentiometer mechanical stops should be limiting dial travel.

7) Set the frequency dial to 0.8 and adjust control R109 to obtain a period of 1250 milliseconds. Check

the setting made in step 6 and,

if

necessary, repeat

step 6.

I€

R109 has insufficient range, center the control mechanically and repeat steps electrically center the adjustment range of which can then

8)

Check the calibration of the "X1" range. The out-

put frequency should

be

used to make any final adjustments.

be

within +2% of the dial reading over the entire range. Adjust resistor values for R26. The location of R26

6

and 7. This will

by

substituting different

R109

is

shown in Figure 4-3.

Turn

3)

the 202A on, set the line voltage to 115 volts, turn the FUNCTION switch to "SQUARE", and allow at least a

1 hour warm-up period.

4) Adjust power supply, then adjust DC Balance

and Distortion.

5) Determine the ratio between the two frequencies

obtained with the frequency dial at "0.8" and

"12"

with the RANGE switch at "Xl".

Frequency determination

is

most easily accomplished

by measuring the period of the unknown frequency.

An electronic or 524B will be needed. A frequency of

kounter such as @Model 522B, 523B,

0.8

cps

has

a period of 1250 milliseconds while 12 cps has a period of 83.3 milliseconds.

6)

The ratio obtained in step 5 must

be

15

to

1. Adjust

by loosening the coupler between the dial and poten-

tiometer

(R58) shafts. See Figure 4-4 for coupler access hole location. Rotate one shaft with respect to the other to obtain a period of 83.3 milliseconds

12.

with a dial reading of

Tighten both set screws in

the coupler.

SHOWN

X.01 POSITION.

TIE-POINT (CENTER) WAFER NOT SHOWN. CKT.

REFERENCES SAME AS ON SCHEMATIC.

Figure 4-3.

Use only

*1%

Rear View of S2 Range Switch

deposited carbon film resistors. Conventional type composition resistors can be used for series pads provided they do not exceed

10% of the

total value for R26. The extra tie point wafer on the

switch may be used for mounting resistors in series.

The value of R26 will usually be between 100,000

and 1,500,000 ohms.

9) Check the calibration of the other ranges in a like manner. Adjust R24 for "X.

1"

range, R27 for the "Xl0" range, and R28 for

"X100" range. The values of these resistors

the

"X. 01" range, R25 for the

will usually be within 400,000 ohms of the value of

R26.

Sect.

IV

Page

9

Use only

*l%

deposited carbon film resistors for R24,

R25, R27, and R28 as previously described for R26.

Again common type composition resistors can

used for series pads provided they

do

not exceed 10%

be

of the total resistance value. On

the "X10OV' range only, a fixed High-Q ceramic or silver mica capacitor connected in parallel with R28 will compress the high frequency end of the

be

is

used.

band. The maximum value for this capacitor

300 ppf and any value less than this may

is

This capacitor

is

and

not shown on the schematic diagram.

not required in all instruments

10) Replace the cabinet or the top and bottom cover.

4-14

REPLACEMENT OF R58

POTENTIOMETER

Replacement of the frequency control potentiometer involves two basic operations:

1) The mechanical procedure for replacing a de-

fective potentiometer with a new one.

2) The necessary electrical adjustments described in paragraph 4-13.

All

necessary specialized instructions are included

with the replacement potentiometer.

COUPLER

ACCESS

Figure

4-4.

Model

202A

Top

View Cover Removed

Figure

4-5.

Model

202A

Bottom View Bottom Plate Removed

Figure

4-6.

Model 202A Function Generator and Amplifier

BLACK TI

PRI.

I

WHITE

115V

PRI.

2

BLACK TI

PRI.

I

BROWN

2

PRI.

TRANSFORMER DETAIL

NOTES: (APPLY TO FUNCTION GENERATOR 8 AMPLIFIER SECTION AS WELL AS TO POWER SUPPLY SECTION).

K

=

CONDITIONS OF DC VOLTAGE MEASUREMENT:

1. 115/230V. 50/1000'L POWER SUPPLY

2.

MEASURED BETWEEN THE INDICATED POINTS AND B- VOLTAGES. WITH A VOLTMETER OF l22MEGOHMS INPUT RESISTANCE. (0- IS ANY BLACK LEAD IN POWER SUPPLY EXCEPT TI R78 8 R79 PRIMARY START.)

3. PANEL CONTROLS SET AS FOLLOWS: RANGE AT XIO.

FREQUENCY AT FUNCTION AT SINE. AMPLITUDE AT MAX.

*

ELECTRICAL VALUE ADJUSTED AT THE FACTORY. AVERAGE VALUE SHOWN. PART MAY

5.

BE OMITTED.

1000 OHMS

M = I MEGOHM

+

MAIN (EXTERNAL) CHASSIS,ISOLATED FROM POWER SUPPLY

rf7

INTERNAL CHASSIS,ONE POINT CONNECTION TO DIVIDER

POWER SUPPLY RETURN) IS

CAPACITY IN L)VF UNLESS OTHERWISE NOTED.

2024

-PS

-5311A

NOT CONNECTED TO CHASSIS.

Figure

47

Model

202A

Power

Supply

Sect. V Page

1

TABLE

NOTE

Any changes in the Table of Replaceable Parts will be listed on a Production Change sheet at the front of this manual.

When ordering parts from the factory always include

the following information:

OF

REPLACEABLE PARTS

SECTION

V

Instrument Model Number Serial Number

@

Stock Number of Part

Description of Part

Sect.

V

Page

2

TABLE

OF

REPLACEABLE PARTS

#

Total

quantity

used

in

the

instrument.

Sect.

V

Page

3

TABLE

OF

REPLACEABLE PARTS

#

Total

quantity

used

in

the

instrument.

Sect.

V

Page

4

TABLE

OF

REPLACEABLE PARTS

#

Total

quantity used

in

the

instrument.

Sect.

V

Page

5

TABLE

OF

REPLACEABLE PARTS

Sect.

V

Page

6

TABLE

OF

REPLACEABLE PARTS

#

Total

quantity

used

in

the

instrument.

Sect.

V

Page

7

TABLE

OF

REPLACEABLE PARTS

Sect. V Page 8

*

CIRCUIT

REF.

DESCRIPTION,

TABLE OF REPLACEABLE PARTS

@

STOCK

MFR.

*

&

MFR. DESIGNATION

NO.

#

R83

R84a-f, R85a-f

R86 thru R90

R91

R92

R9 3

R9 4

R9 5

R96,97

R98,99

This circuit reference

not assigned

Resistor: fixed, wirewound HP* These circuit references

not assigned

Resistor: fixed, wirewound,

2500 ohms

Same as R62

Resistor: variable, composition, 2 sections,

1

megohmlsect. *20%, 114

Same as R53

Resistor: fixed, deposited carbon,

67,500 ohms

Same as R6

Resistor: fixed, deposited carbon,

15,800 ohms

*lo%,

*l%, 112

*1%,

10

W

1

W

S*

BO*

NN*

20%-26C

26-7

210-77

33-67.5K

31-15.8K

2

1

2

R100, 101 102

R103

R104,105

R106

R107

R108

*

See "List

#

Total quantity

These circuit references

not assigned

Resistor: fixed, composition, 4-1800

B

AC

*

I.

26-124

1800 ohms

Resistor: fixed, wirewound,

14, 500 ohms,

Same as R15

Same as R16

Same as R15

of

Manufacturers Code Letters For Replaceable Parts Tableu.

used in the instrument.

*lo%,

A%,

1

W

3

W

1

2

TABLE OF REPLACEABLE PARTS

Sect. V Page 9

CIRCUIT

REF.

*

&

DESCRIPTION, MFR.

Resistor: f ixed, deposited carbon

920 ohms

Resistor: fixed, deposited carbon,

13,200 ohms

Resistor: fixed, deposited carbon,

37,400 ohms

Resistor: fixed, deposited carbon,

71,560 ohms

Resistor: fixed, deposited carbon,

115,000 ohms

This circuit reference not

assigned

Resistor: fixed, deposited carbon,

214,000 ohms

Resistor: f ixed, composition

4.7 megohms

Resistor: variable, composition

500,000 ohms, linear taper

Resistor: variable, wirewound,

500 ohms, 2 W, linear

A%, 112 W

+I%, 112 W

*1%, 112 W

A%, 112 W

+I%, 112 W

A%, 112 W

+lo%, 112 W

MFR. DESIGNATION

NN*

B*

G*

BO*

@

STOCI NO.

I

Switch, toggle: SPST

1

s1

Range Switch Assembly: (includes R24

1

s2

I

v3

I

v4

I

*

See "List of Manufacturers Code Letters For Replaceable

#

Total quantity

1

I

thru R29, ClS thru C18) HP*

Function Switch Assembly: (includes 202A-19B

R94, R95) HP* Transformer, power Transformer, pulse Transformer, pulse

Tube, electron: Tube, electron: 6AL5 Tube, electron: 6C4 Tube, electron: OA2 Tube, electron: OA3

Same

as

V3

used

in

the

6AU6

instrument.

D*

310-11

I

202A-19W

Paeco 910-79

Paeco 913-2

HP* 202A-60B ZZ* 212-6AU6 ZZ* 202A-95B

I

ZZ* 1212-6C4 ZZ* 212-OM ZZ* 212-OA3

1

Parta

Tablew.

Sect.

V

Page

10

TABLE

OF

REPLACEABLE PARTS

Sect. V Page

11

TABLE

OF

REPLACEABLE PARTS

#

Total

quantity used in the instrument.

LIST OF CODE LETTERS USED IN TABLE OF REPLACEABLE PARTS

TO

DESIGNATE THE MANUFACTURERS

CODE

LER

MANUFACTURER

Aerovox Corp. Allen-Bradley Co. Amperite Co.

&

Arrow, Hart

Bussman Manufacturing Co. Carborundum Co. Centralab Cinch-Jones Mfg. Co.

Hewlett-Packard Co. Clarostat Mfg. Co. Cornell Dubilier Elec. Co.

Hi-Q Division of Aerovox

Erie Resistor Corp.

Fed. Telephone General Electric Co. General Electric Supply Corp. Girard-Hopkins Industrial Products Co. lnternational Resistance Co. Lectrohm Inc. Littlefuse Inc. Maguire Industries Inc. Micamold Radio Corp. Oak Manufacturing Co. P. R. Mallory Co., Inc.

Radio Corp. of America Sangamo Electric Co. Sarkes Signal Indicator Co. Sprague Electric Co. Stackpole Carbon Co. Sylvania Electric Products Co. Western Electric Co. Wilkor Products, Inc. Amphenol Dial Light Co. of America Leecraft Manufacturing Co. Switchcraft, Inc. Gremar Manufacturing Carad Corp. Electra Manufacturing Co.

Acro Manufacturing Co. Alliance Manufacturing Co. Arco Electronics, Inc. Astron Corp. Axel Brothers Inc. Belden Manufacturing Co.

Bird Electronics Corp.

Barber Bud Radio Inc. Allen D. Cinema Engineering Co. Any brand tube meeting

RETMA standards.

Corning Glass Works Dale Products, lnc. The Drake Mfg. Co. Elco Corp.

Hugh H. Eby Co.

Thomas A. Edison, Inc. Fansteel Metallurgical Corp. General Ceramics The Gudeman Co.

Hegeman

&

Radio Corp.

Tarzian

Colman Co.

Cardwell Mfg. Co.

&

Steatite Corp.

Co.

ADDRESS New

Bedford, Mass. Milwaukee New York, N. Y. Hartford, Conn. St. Louis, Mo. Niagara Falls, N. Y. Milwaukee

Chicago 24,

Palo Alto, Calif. Dover, N. H. South Plainfield, N. J. Olean, N. Y. Erie 6, Pa.

Clifton, N. J.

Schenectady 5, N. Y. San Francisco, Calif.

Oakland, Calif.

Danbury, Conn. Philadelphia 8, Pa.

Chicago 20,

Des Plainer,

Greenwich, Conn.

Brooklyn 37, N. Y.

Chicago 10,

Indianapolis, Ind. Harrison, N. J.

Marion, Bloomington. Ind. Brooklyn 37, N. Y. North Adams, Mass. St. Marys. Pa. Warren, Pa.

New York 5, N. Y.

Cleveland, Ohio Chicago 50, Brooklyn 37, N. Y.

New York, Chicago 22, Wakefield, Mass.

Redwood City, Calif. Kansas City, Columbus 16, Ohio

Alliance, Ohio

New York 13, N. Y. East Newark, N. J. Long Island City, N. Y.

Chicago Cleveland 14, Ohio

Rockford,

Cleveland 3, Ohio

Plainville, Conn. Burbank. Calif.

Corning, N. Y. Columbus, Neb. Chicago 22,

Philadelphia 24, Pa. Philadelphia

West Orange. N. J.

North Chicago. Keasbey, N. J.

Sunnyvale, Calif.

Ill.

44,

Ill.

4,

N.

I,

111.

Ill.

111.

44,

Wis.

111.

Y.

Ma.

Pa.

Ill.

CODE

LETTER MANUFACTURER

Hammerlund Mfg. Co., Inc. Industrial Condenser Corp.

lnsuline Corp. of America Jennings Radio Mfg. Corp. E. F. Johnson Co. Lenz Electric Mfg. Co. Micro-Switch Mechanical Industries Prod. Co. Model Eng. & Mfg., Inc.

The Muter Co.

Ohmite Mfg. Co.

Resistance Products Co.

Radio Condenser Co. Shallcross Manufacturing Co. Solar Manufacturing Co. Sealectro Corp.

Spencer Thermostat Stevens Manufacturing Co. Torrington Manufacturing Co. Vector Electronic Co. Weston Electrical Inst. Corp. Advance Electric & Relay Co.

E.

I.

DuPont

Electronics Tube Corp.

Aircraft Radio Corp. Allied Control Co., Inc. Augat Brothers, Inc. Carter Radio Division CBS Hytron Radio Chicago Telephone Supply

Henry L.

Curtiss-Wright Corp. Allen B. Excel Transformer Co. General Radio Co. Hughes Aircraft Co. lnternational Rectifier Corp.

James Knights Co.

Mueller Electric Co. Precision Thermometer Radio Essentials Inc.

Raytheon Manufacturing Co. Tung-Sol Lamp Works, Inc. Varian Associates Victory Engineering Corp. Weckesser Co. Wilco Corporation Winchester Electronics, Inc.

Malco Tool Oxford Electric Corp. Camloc-Fastener Corp. George K. Garrett

Union Switch

Radio Receptor Automatic

Bassick Co.

Birnbach Radio Co.

Fischer Specialties Telefunken Potter-Brumfield Co. Cannon Electric

Dynac. Inc. Good-All Electric Mfg. Co.

Crowley Co., Inc.

DuMont Labs

&

Die

&

Signal

&

Precision Mfg. Co.

(c/o MVM, Inc.)

Co.

&

Electric

&

Inst. Co.

ADDRESS

New York

Chicago 18,

Manchester, N. San Jose, Calif. Waseca, Minn. Chicago

Freeport,

-

Akron 8, Ohio

Huntington, Ind. Chicago Skokie. Harrisburg, Pa. Camden 3, N. J. Collingdale, Pa. Lor Angeles 58, Calif. New Rochelle, N. Y. Attleboro, Mass. Mansfield, Ohio Van Nuys, Calif. Lor Angeles 65, Calif. Newark Bgrbank, Calif. San Francisco, Calif. Philadelphia 18, Pa. Boonton, N. J. New York 2

Attleboro, Mass. Chicago,

Danvers, Mass. Elkhart, Ind. West Orange, N. J.

Carlstadt, N. J. Clifton, N. J.

Oakland, Calif.

Cambridge 39, Mass. Culver City, Calif.

El Segundo, Calif.

Sandwich, Cleveland, Ohio

Philadelphia 30, Pa.

Mt. Vernon, N. Y. Newton, Mass. Newark

Polo Alto, Calif.

Union, N. J. Chicago 30,

Indianapolis, Ind.

Santa Monica, Calif. Lor Angeles 42. Calif. Chicago 15, Paramus, N. J. Philadelphra 34, Pa. Swissvale, Pa. New York Yonkers, Bridgeport 2, Conn. New York 13, N. Y. Cincinnati 6, Ohio New York, N. Y. Princeton, Ind. Los Angeles, Calif. Palo Alto, Calif. Ogallala, Nebr.

47,

Ill.

5,

Ill.

5,

Ill.

4,

N.

I,

N. Y.

111.

N. J.

1,

Ill.

N. J.

111.

I I,

Y.

111.

H.

N. Y.

CLAIM FOR DAMAGE IN SHIPMENT

The instrument should be tested as soon as it is received. If it fails to operate properly, or is damaged in any way, a report of the damage should be obtained by the claim agent, and this report should

be forwarded to us. We will then advise you of the disposition to be made of the

equipment and arrange for repair or replacement. Include model number and serial

number when referring to this instrument for any reason.

claim should be filed with the carrier. A full

WARRANTY

Hewlett-Packard Company warrants each instrument manufactured by them to be free from defects in material and workmanship. Our liability under this warranty

is limited to servicing or adjusting any instrument returned to the factory for that purpose and to replace any defective parts thereof. Klystron tubes as well as other electron tubes, fuses and batteries are specifically excluded from any liability. This

warranty is effective for one year after delivery to the original purchaser when the

instrument is returned, transportation charges prepaid by the original purchaser,

and when upon our examination it is disclosed to our satisfaction to be defective. If

the fault has been caused by misuse or abnormal conditions of operation, repairs

will be billed at cost. In this case, an estimate will be submitted before the work is started.

If any fault develops, the following steps should be taken:

1.

Notify us, giving full details of the difficulty, and include the model number and serial number. On receipt of this information, we will give you service data or shipping instructions.

2.

On receipt of shipping instructions, forward the instrument prepaid, to the

factory or to the authorized repair station indicated on the instructions. If requested,

an estimate of the charges will be made before the work begins provided the instrument is not covered by the warranty.

SHIPPING

All shipments of Hewlett-Packard instruments should be made via Truck or

Railway Express. The instruments should be packed in a strong exterior container

and surrounded by two or three inches of excelsior or similar shock-absorbing material.

DO

NOT HESITATE TO

275

PAGE MILL

ROAD

CABLE

CALL

PAL0 ALTO.CALIF.

"HEWPACK"

ON US

USA

@

MANUAL CHANGES

MODEL 202A

LOW FREQUENCY FUNCTION GENERATOR

R59

S2

: :

6411

:.

ERRATA

Serial

6238, 6369,

c33:

R24

t

hru Delete

:

R28 R24A,25A9

26A927A:

R28A

R24B9 25B9

:

26B927B, 28B

:

Add "Electrical value adjusted at the factory,"

and above; also Serials 6065, 6211, 6218, 6234,

6375, 6384, 6388, 6392 and 6404:

Change to range switch assembly; 202A-l9C, Mfr,,

Change to capacitor, variable, ceramic, 7-45uuf9 500 vdcw;

Add resistor, fixed, deposited carbon, 900,000 ohms

-

m,

Electrical value adjusted at the factory, Add resistor, fixed, deposited carbon, 800,000 ohms

m9

Electrical value ad,justed at the factoryo

-

Add resistor, variable, composition,

-

+30%,

See partial schematic below;

1

linear taper; -hp- Stock Noo 210-111,

-hp-

W;

-hp- Stock

W;

-hp- Stock Noo 31-800K, Mfr.,

HP

Stock

NO,

13-1,

31-900K,

-hp-

Mfr,,

Stock No,

L

NN

1

megohm

Mfr.,

G

0

*

Model 202A - Page 2

ERRATA

Section

Serial 67529

:

IV-13

Step

8)

9)

6800

67539

C1,2: Change to capacitor, fixed, electrolytic, 20uf,

FREQUENCY RATIO AND CALIBRATION PROCEDURE

Check calibration of the "Xl" range, The output frequency should be within

ing over the entire range. Adjust

sary. Check the calibration of the other ranges, Adjust

R24B for the "X.01" range, R25B for the "X,ltl range, R27B for the "X10" range and R28B for the "X100" range.

On

the "X100" range only, adjust C33 to calibrate

the high end of the band,

and above; also Serials 6411, 6747, 6750,

67549

450

Add

--

20uf/sect,

67559

vdcw; -hp- Stock No, 18-20HP, Mfr., CC capacitor, fixed, electrolytic, 2 sections,

6756,

450

vdcw; -hp- Stock No, 18-22HP, Mfr,, CC

67579

22% of the dial read-

R26B if neces-

6758:

6751,

R120

thru

R123

-

Add

:

-

resistor, fixed, composition,

+lo%, 2 See partial schematic below:

W;

-hp- Stock No. 25-150K, Mfro, B

150,000

ohms