HP 467A Service-Handbuch

|

OPERATING

AND

SERVICE

MANUAL

(HP

PART

NO.

00467-90003)

MODEL

467A

POWER

AMPLIFIER/SUPPLY

SERIALS

PREFIXED:

444.

`

Copyright

Hewlett-Packard

Company

1965

Р.О.

Box

301,

Loveland, Colorado,

80537

U.S.A.

Printed

AUG

1969

hick

et

eet

ae

Model

467A

Section

I

SECTION

1

GENERAL

INFORMATION

1-1.

DESCRIPTION.

1-2.

The

solid

state

467A

Power

Amplifier/Supply

is

a

10

watt

peak

power

amplifier

and

-20

to

+20

voit

de

power

supply.

The

power

amplifier

has

a

wide

bandwidth

with

low

de

drift

from

de

to

1

MHz

offering

wide

applications

wherever

a

power

source

is

ге-

quired.

Low

distortion

(<0,

01%),

low

drift

and

0.

3%

gain

accuracy

are

obtained

with

high

quality

compo-

nents

and

multiple

feedback

techniques.

The

gain

of

the

amplifier

may

be

varied

between

one

and

ten

by

a

front

panel

switch

which

provides

fixed

gain

steps

accurate

to

+0.

3%.

A

variable

gain

control

enables

the

user

to

set

the

gain

anywhere

between

zero

and

ten

witha

resolution

of

better

than

0.1%

of

full

output.

Table

1-1

gives

the

specifications

for

the

467A

Power

Amplifier

/Supply.

1-3.

OUTPUT

CAPABILITY.

1-4.

An

output

greater

than

20

volts

peak

and

0.5

ampere

peak

is

available

from

ас

up

to

1

MHz.

The

amplifier

is

protected

at

all

times

from

short

cir-

cults.

The

input

circuit

of

the

467A

is

protected

against

damage

from

voltages

up

to

200

volts

р-р.

Input

and

output

connectors

are

provided

at

the

front

and

rear

of

the

instrument.

The

amplifier

is

a

three

terminal

device

isolated

from

chassis

and

may

be

floated

up

to

200

volts

de

above

chassis

ground.

1-5.

POWER

SUPPLY.

1-6.

A

front

panel

switch

converts

the

amplifier

to

a

power

supply

that

delivers

+20

volts

de

at

currents

ир

to

+0.

5

ampere.

The

output

level

is

controlled

by

a

potentiometer

which

permits

voltages

to

be

set

with

resolution

of

0.1%

of

full

scale.

Full

scale

ranges

of

+1,+2,44,

+10,

and+20

volts

are

selected

by

the

front

panel

range

switch.

1-7.

INSTRUMENT

IDENTIFICATION.

1-8.

Hewlett-Packarduses

a

two-section

eight-digit

serial

number

(000-00000).

If

the

first

three

digits

of

the

serial

number

on

your

instrument

do

not

agree

with

those

on

the

title

page

of

this

manual,

change

sheets

supplied

withthe

manual

will

define

differences

between

your

instrument

andthe

Model

467A

described

in

this

manual,

1-1

Model

467A

Section

П

SECTION

И

INSTALLATION

2-1.

INSPECTION.

2-2.

Upon

receipt,

unpack

and

inspect

the

instrument

for

mechanical

and

electrical

damage.

Mechanical

inspection

includes

visually

checking

the

instrument

for

scratched

and

warped

surfaces,

damaged

control

knobs,

switches,

and

indicators,

and

signs

of

weather

exposure.

The

electrical

inspection

involves

checking

instrument

operation

against

specification

values

given

in

Table

1-1.

Refer

to

Paragraph

5-5.

NOTE

in

case

of

mechanical

damage,

file

a

claim

with

the

carrier

im-

mediately.

If

an

electrical

mai-

function

occurs,

refer

to

the

war-

ranty

page

in

the

front

of

this

manual,

2-3.

INSTALLATION.

2-4.

The

Model

467A

is

a

submodular

unit

that

can

be

mounted

on

a

bench,

or

in

a

rack

or

cabinet.

It

is

shipped

with

plastic

feet

and

tilt

stand

in

place,

ready

for

bench

use.

When

used

as

a

single

submodule,

it

is

utilized

as

a

bench

unit

only.

When

used

in

com-

bination

with

other

submodule

units,

a

rack

adapter

frame

or

combining.

case

is

available

for

rack

or

cabinet

mounting.

The

instrument

should

be

installed

where

ambient

temperature

does

not

exceed

30°C

(122°R).

2-5.

POWER

REQUIREMENTS.

2-6.

The

Model

467A

can

be

operated

from

a

115

or

230

ac

volt

410%

source

at

50

to

400

Hz.

Power

con-

nections

are

made

by

plugging

the

power

cable

(вир-

plied

with

the

instrument)

into

the

AC

POWER

male

connector

at

the

rear

of

the

unit

and

the

appropriate

power

receptacle.

An

0.8

ampere

slow-blow

fuse

is

used

for

115

and

230

volt

operation.

BEFORE

PLUGGING

POWER

CABLEINTO

THE

RECEPTACLE,

DETERMINE

THAT

THE

LINE

VOLTAGE

SWITCH

ON

THE

REAR

PANEL

IS

SET

PROPERLY

TO

ACCEPT

THAT

VOLTAGE

(115

OR

230).

2-7.

THREE-CONDUCTOR

POWER

CABLE.

2-8.

АП

Hewlett-Packard

instruments

are

equipped

with

a

three-conductor

power

cable,

which

complies

with

the

recommendations

of

the

National

Electrical

Manufacturer's

Association

(NEMA)

for

rack

and

cabinet

grounding.

The

offset

on

the

cable

is

the

ground

connector.

NOTE

When

operating

from

a

two-con-

tact

outlet,

the

grounding

feature

can

be

maintained

by

using

a

three-

pronged

adapter

and

connecting

the

green

pigtail

on

the

adapter

to

ground.

2-9.

REPACKAGING

FOR

SHIPMENT.

2-10.

The

following

paragraphs

contain

a

general

guide

for

repackaging

of

the

instrument

for

shipment.

Re-

fer

to

Paragraph

2-11

if

the

original

container

is

to

be

used;

2-12

if

it

is

not.

If

you

have

any

questions,

contact

your

local

-hp-

Sales

and

Service

Office.

(See

Appendix

В

for

office

locations.

}

NOTE

If

the

instrument

is

to

be

shipped

to

Hewlett-Packard

for

service

or

repair,

attach

a

tag

to

the

in-

strument

identifying

the

owner

and

indicating

the

service

or

repair

to

be

accomplished;

include

the

model

number

and

full

serial

number

of

the

instrument.

In

any

correspondence,

identify

the

instrument

by

model

number,

serial

number,

and

serial

number

prefix.

2-11.

If

original

container

is

to

be

used,

proceed

as

follows:

а.

Place

instrument

іп

original

container

if

avail-

able.

If

original

container

is

not

available,

one

canbe

purchased

from

your

nearest

~hp-

Sales

and

Service

Office.

b.

Ensure

that

container

is

well

sealed

with

strong

tape

or

metal

bands.

2-12.

If

original

container

is

not

to

be

used,

proceed

as

follows:

a.

Wrap

instrument

in

heavy

paper

or

plastic

before

placing

in

an

inner

container.

b.

Place

packing

material

around

all

sides

of

instrument

and

protect

panel

face

with

card-

board

strips.

с.

Place

instrument

and

inner

container

in

a

heavy

carton

or

wooden

box

and

seal

with

strong

tape

or

metal

bands.

d.

Mark

shipping

container

with

"DELICATE

INSTRUMENT,"

"FRAGILE"

etc,

2-3

Model

467A

SECTION

INSTRUCTIONS

OPERATING

3-1.

GENERAL.

3-2.

The

Model

467A

Power

Amplifier/Supply

canbe

operated

as

a

power

amplifier

or

a

power

supply.

Controls

оп

the

front

panel

provide:

(1}

selection

of

either

operating

mode

and

(2)

selection

of

fixed

or

variable

amplifier

gain

and

power

supply

ranges.

3-3.

DESCRIPTION

OF

CONTROLS.

3-4,

Figure

3-1

gives

the

description

and

function

of

the

467A

controls,

indicators

and

connectors,

3-5.

OPERATING

INSTRUCTIONS.

3-6.

When

operated

as

a

power

amplifier

(поп-іпуегі-

ing),

the

Model

467A

has

four

calibrated

gain

factors

(AMPLIFIER:

X1,

X2,

X5,

and

X10)

and

provides

a

maximum

output

power

of

10

watts

peak

for

input

fre-

quencies

between

de

and

1

MHz.

Accuracy

of

+0.3%

from

дс

to

10

kHzis

obtained

when

operating

into

a

load

of

40

ohms

or

greater.

As

a

power

supply

(regu-

lated),

the

instrument

can

be

operated

in

five

ranges

of

plus

or

minus

output

voltages

(SUPPLY:

+1,

+2,

+4,

+10,

and

+20).

The

amplifier

gain,

or

the

+

de

output

can

be

varied

with

the

VAR.

GAIN/VOLTS

ADJ.

control.

The

input

and

output

terminals

are

de

isolated

from

earth

ground.

Connection

of

a

grounding

strap

between

the

power

line

ground

(-2)

and

(44

terminals

references

both

the

INPUT

and

OUTPUT

(,

terminals

to

earth

ground.

3-7.

AMPLIFIER

OPERATING

INSTRUCTIONS,

a.

Set the

AMPLIFIER/SUPPLY

control

to

the

AMPLIFIER

position,

selecting

the

desired

gain

setting

(VAR.,

X1,

X2,

X5,

or

X10).

b.

Set

the

LINE

switch

to

ON.

NOTE

To

assure

maximum

stability,

allow

the

instrument

to

warm

up

for

30

minutes.

Section

Ш

с.

Connect

DC

Voltmeter

(-hp-

Model

412A)

to

the

467A

OUTPUT

terminalis;

adjust

the

ZERO

control

to

obtain

a

zero

de

output.

d.

Connect

the

467A

OUTPUT

terminals

tothe

de-

vice

to

which

the

amplified

signal

is

being

ap-

plied.

e.

Connect

the

signal

to

be

amplified

to

the

467A

INPUT

terminals.

3-8.

POWERSUPPLY

OPERATING

INSTRUCTIONS.

a.

Connect

the

467A

OUTPUT

terminals

to

the

de-

vice

towhichthe

power

supply

is

being

applied.

b.

Set

467A

AMPLIFIER/SUPPLY

control

in

the

SUPPLY

range

to

the

desired

voltage

setting

(+1,

+2,

+4,

+10,

or

+20).

c.

Set

the

LINE

switch

to

ON.

NOTE

To

assure

maximum

stabilization,

allow

the

instrument

to

warm

up

for

30

minutes.

4.

Usingthe

VAR.

GAIN

VOLTS

ADJ.

control,

ad-

just

the

voltage

to

the

desired

level.

NOTE

The

VAR.

GAIN

VOLTS

ADJ.

con-

trol

is

used

for

both

coarse

and

fine

adjustments.

Coarse

adjust

is

made

after

either

limit

of

the

fine

adjust

is

reached,

Full

CCW

position

produces

maximum

negative

voltage.

Full

CW

position

produces

maximum

positive

voltage,

Section

HI

Model

467A

POWER

AMPLIFIER

HEWLETT:

PACKARD

467А-В-

0900

LINE

ON:

switches

voltage

on;

indicator

glows

when

ac

line

voltage

is

ОМ.

(2)

AMPLIFIER/SUPPLY:

selects

power

ampli-

fier

or

power

supply

mode

of

operation

for

the

instrument.

AMPLIFIER

(X1,

X2,

X5,

X10):

selects

the

fixed

step

gain

factor.

AMPLIFIER

(VAR.

):

operates

in

conjunction

with

VAR.GAIN

to

provide

variable

control

of

amplifier

gainanywhere

between

zero

and

X10.

SUPPLY:

selects

full

scale

ranges

of

+1, +2,

+4,

+10,

or

+20

volts.

(3)

VAR

GAIN/VOLTS

ADJ.:

operates

in

conjunc-

3-2

tion

with

AMPLIFIER/SUPPLY

control

to

рго-

vide

variable

control

ofamplifier

gain

or

selec-

tion

of

+

de

output

voltage,

VAR.

GAIN:

operates

in

conjunction

with

AM-

PLIFIER

(selector

in

VAR.

position)

to

pro-

vide

variable

control

of

amplifier

gain

any-

where

between

zero

and

X10.

VOLTS

ADJ.:

operates

in

conjunction

with

SUPPLY

control

position

to

provide

variable

control

of

de

output

voltage

anywhere

between

0

volts

and

+20

volts.

(4)

INPUT:

banana-type

connectors

that

provide

signal

inputandcircuit

common

input

connec-

tions

for the

instrument.

ZERO:

a

screwdriver

adjust

that

provides

com-

pensation

for

de

offset,

or

unbalance,

with

no

signal

applied

to

the

467A

INPUT

terminals.

(6)

OUTPUT:

рапапа-іуре

connectors

that

provide

signal

output

circuit

commonand

chassis

output

connections

for

the

instrument.

Figure

3-1.

Front

panel

Controls,

Indicators

and

Connectors

о

wees)

@

н5/230%

0.8A

467А-В-009!

(1)

INPUT

and

OUTPUT

connectors;

these

ВМС

power

transformer.

This

fuse

isusedfor

both

connectors

are

connected

in

parallel

with

the

115

v

and

230

v

operation.

INPUT

and

OUTPUT

terminals

on

the

front

|

в

panel.

©)

Power

Connector:

accepts

a

3-wire

power

cable

with

safety

ground.

FUSE:

contains

a

fuse

which

provides

protec~

(2)

Line

Voltage:

atwo-position

slide

switch;

sets

tion

for

the

primary

circuit

of

the

instrument

the

467A

for

115

or

230

volt

operation.

Figure

3-2.

Rear

Panel

Controls

and

Connectors

Model

467A

Section

Ш

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Model

4674

Section

IV

SECTION

IV

THEORY

OF

4-1.

INTRODUCTION.

4-2.

The

Model

467A

Amplifier

circuits

include

a

high

frequency

amplifier,

a

low

frequency

amplifier,

a

two-stage

differential

amplifier,

a

driver

amplifier,

and

two

power

amplifier

stages.

These

circuits

pro-

vide

two

modes

of

operation,

the

power

amplifier

mode

and

the

power

supply

mode.

4-3,

Whenthe

AMPLIFIER/SUPPLY

switch

is

in

the

AMPLIFIER

position,

the

gain

canbe

set

in

fixed

steps

of

X1, X2,

X5

and

X10,

When

the

switch

is

in

the

AMPLIFIER/VAR

position,

the

VAR

GAIN/VOL

TS

ADJ

control

can

be

used

to

set

the

amplifier

gain

to

any

value

between

zero

and

ten.

The

input

signal

is

applied

to

the

attenuator,

which

selects

the

gain

to

be

used

by

the

instrument

amplifier

circuitry.

Ac

and

de

feedback

stabilize

the

amplifier

gain.

Compensation

for

de

offset,

or

unbalance,is

provided by

a

ZERO

adjust

control

on

the

front

panel.

4-4,

Whenthe

AMPLIFIER/SUPPLY

switch

is

in

the

SUPPLY

position,

the

amplifier

provides

five

power

supply

voltage

ranges:

+1,

+2,

+4,

+10

and

+20

volts,

variable

from

plus

through

zero

to

minus

for

each

range,

An

internal

de

reference

voltage

(plus

or

minus)

is

applied

tothe

amplifier

portion,

which

pro-

vides

a

regulated

dc

voltage

at

the

OUTPUT

terminais

of

the

instrument.

4-5.

BLOCK

DIAGRAM

DESCRIPTION.

4-6.

Figure

4-1

shows

the

block

diagram

for the

4674.

The

input

signal

is

applied

to

the

high

and

low

frequency

amplifiers.

The

high

frequency

amplifier

(Q101)

amplifies

the

ac

signal;

the

low

frequency

am~

plifier

(Q108

through

Q110)

amplifies

the

дс

and

low

frequency

signals.

The

amplified

input

signal

is

then

applied

through

the

differential

amplifier

(Q102

and

Q103),

amplifier

(Q104),

and

driver

amplifier

(Q105)

to

emitter

followers

(Q106

and

Q107).

Power

ampli-

fiers

Qi

and

Q2

(driven

by

Q106)

and

Q3

and

Q4

(driven

by

Q107)

provide

a

balanced

signal

to

the

OUTPUT

connectors.

4-7.

At

frequencies

above

1

MHz,

negative

feedback

from

the

driver

amplifier

Q105

is

applied

to

Q101

through

C122

and

R129

to

provide

a

decrease

іп

dis~

tortion

and

remove

the

power

amplifiers

from

the

feedback

loop.

Negative

feedback

from

Q105

is

applied

to

differential

amplifiers

Q102

and

Q103

through

R120,

CiiSand

R119

to

improve

frequency

response

of

the

instrument.

Gain

control

for

high

frequency

amplifier

Q101

is

supplied

from

the

output

of

the

power

amplifiers

(Q1

through

Q4)

through

R148

and

R130,

4-8.

At

frequencies

between

4с

and

50

KHz,

negative

feedback

from

the

output

provides

de

gain

control

and

balance

adjust

for

the

low

frequency

amplifiers

Q108

through

Q110.

ZERO

adjust

R5

provides

compensation

for

dc

unbalance

of

the

signal

applied

to

the

low

fre-

quency

amplifiers.

Relay

K1

protects

the

external

load

against

current

surges

during

turn-on

and

turn-off.

OPERATION

4-9.

SCHEMATIC

DIAGRAM

ODECRIPTION.

4-10.

The

following

paragraphs

give

а

detailed

descrip-

tion

of

the

Model

467A

Amplifier

circuits.

Refer

to

Figures

5-13.and5-14,

Section

V,

for

the

schematic

diagrams

of

the

instrument.

4-11.

HIGH

FREQUENCY

AMPLIFIER.

4-12,

Trimmer

capacitors

C301,

C303

and

C305

can

be

adjusted

to

provide

the

desired

frequency

response

characteristics

for

the

instrument.

Ac

input

signals

from

the

attenuator

are

applied

through

C101

to

the

high

frequency

amplifier

Q101.

The

signal

is

amplified

by

9101

and

coupled

through

C104

to

the

base

circuit

of

Q102.

The

RC

networks,

C105,

R112,

C106

and

R114

are

used

to

improve

the

frequency

response

characteristics

ofthe

amplifier

Q102.

The

bias

volt-

age

of

Q101

is

determined

by

resistive

divider

R103

and

R104.

Ac

feedback

from

power

amplifiers

(Q1,

Q2,

Q3,

and

Q4)

is

applied

through

R148

to

provide

ac

gain

adjust

for

Q101,

4-13.

LOW

FREQUENCY

AMPLIFIER.

4-14.

When

the

AMPLIFIER/SUPPLY

selector

is

in

the

SUPPLY

position,

+7

and

-7

volts

are

supplied

from

an

internal

reference,

through

resistive

dividers,

to

the

amplifier

input.

Each

SUPPLY

position

(+1,

+2,

+4,

+10

and

+20)

permits

setting

the

de

output

voltage

to

any

+

value

within

the

range

selected.

The

low

frequency

amplifier

circuit

(Q108,

Q109

and

Q110)

am-

plifies

the

de

and

low

frequency

input

signal

and

drives

Q103.

The

bias

voltage

for

the

low

frequency

amplifier

is

controlled

by

R132

and

R133

and

the

ZERO

control

R5.

Transistor

Q110

is

a

current

source

for

the

dif-

ferential

amplifiers

Q108

and

Q109.

Inductors

1101

and

L102

control

the

frequency

response

of

the

low

frequency

amplifier

(at

higher

frequencies)

by

causing

degeneration

of

Q108

and

Q109

emitters.

High

fre-

quencies

present

at

Q109

collector

are

shorted

to

ground

by

C109.

Low

frequency

stabilization

and

over-

allamplifier

gain

(betweende

and

50

KHz)are

provided

by

applying

de

feedback

from

the

OUTPUT

to

Q109

base.

The

ZERO

potentiometer

R5

provides

an

adjust-

ment

to

compensate

for

ас

drift

in

the

instrument.

Varying

R5

changes

the

voltage

at

Q109

base,

thereby

changing

the

output

level

of

the

low

frequency

ampli-

fier,

4-15.

DIFFERENTIAL

AMPLIFIER.

4-16,

Differential

amplifiers

Q102

and

Q103

provide

an

output

proportional

to

the

input

signals

from

the

high

frequency

amplifier

9101

and

the

low

frequency

amplifier

circuit

(Q109

and

Q110).

The

high

fre-

quency

ac

signals

are

coupled

to

Q102

through

C104;

the

de

and

low

frequency

signals

from

the

low

fre-

quency

amplifier

are

direct-coupled

to

differential

amplifier

Q103.

Capacitor

C108

bypasses

any

high

frequency

ac

from

the

low

frequency

amplifier

to

4-1

Section

IV

ground.

C109

bypasses

any

high

frequency

signals

present

at

the

base

of

Q103.

Ac

feedback

from

Q105

collector

circuit

is

applied

through

C115

to

the

base

circuit

of

Q102

for

high

frequency

gain

stabilization.

4-17.

VOLTAGE

AMPLIFIER.

4-18,

The

voltage

amplifier

Q104

supplies

the

majority

of

the

voltage

gain

for

the

instrument.

Degeneration

at

low

frequencies

is

provided

by

R127

in

the

Q104

emitter

circuit;

C116

provides

added

phase

stability

at

high

frequencies.

Current

through

R125

provides

the

bias

current

for

Q105.

Breakdown

diode

CR104

establishes

the

proper

voltage

at

Q104

collector

and

maintains

a

de

signal

path

from

Q104

Collector

to

Q105

base.

4-20.

Driver

amplifier

Q105

is

driven

by

current

am-

plifier

Q104and

supplies

the

signal

to

the

power

out-

put

amplifiers.

Transistors

Q108

and

Q107

are

for-

ward

biased

by

diodes

CR108

through

CR112and

under

no~signal

condition

are

conducting

slightly

to

reduce

cross-over

distortion

in

the

output

signal.

4-21.

OUTPUT

CIRCUITS.

4-22.

Transistors

Q1

through

Q4

provide

а

comple-

mentary

symmetry

output.

Qİ

and

Q2,

driven

by

emitter

follower

Q106,

providea

low

output

impedance.

Q3

and

Q4,

driven

by

Q107,

forma

unity

gain

feed-

backamplifier.

Thiscauses

Q3and

Q4

toactasa

PNP

emitter

follower,

which

is

necessary

to

provide

the

complementary

symmetry

output.

4-23,

EXTERNAL

LOAD

PROTECTION.

4-24.

The

external

load

connected

to

the

467A

is

pro-

tected

during

turn-onand

turn-off,

from

current

surges

and

voltage

transients,

by

relay

KI.

The

relay

con-

tacts

open

the

circuit

tothe

OUTPUT

connectors

when

the

relay

is

de-energized.

When

the

instrument

is

turned

ON,

Ki

remains

de-energized

for

about

300

milliseconds.

This

delay

permits

the

instrument

to

stabilize

before

the

output

is

connected

to

the

load.

The

300

millisecond

delay

is

caused

by

the

RC

time

constant

of

C110

and

R161.

When

the

instrument

is

turned

off,

the

relay

quickly

de-energizes

and

opens

the

circuit

to

the

OUTPUT

connector.

4-2

Model

467A

4-25.

POWER

SUPPLY

CIRCUIT

DESCRIPTION.

4-26.

The

467A

primary

power

supply

consists

of

two

regulated

power

supplies

¢34

and

+34

volts),

and

five

reference

supplies

(+7,

-7,

+15,

-15

and

+30

volts).

Either

115

or

230

volts

ac

is

connected

to

the

instru-

ment

through

switch

51

and

fuse

Fi

to

Т1

primary.

Switch

52

(slide

switch

on

rear

panel)

connects

Т1

primary

windings

in

series

for

230

voit

operation,

or

in

parallel

for

115

volt

operation.

The

LINE

ON

lamp

DSi

glows

when

primary

power

is

applied

tothe

instru-

ment.

4-27.

MINUS

34

VOLT

SUPPLY.

4-28.

Transistor

Q112

in

conjunction

with

R156,

CR129,

and

CR130

provide

a

constant

current

source

which

provides

base

drive

for

Q5

and

Q6.

Q112

also

provides

current

to

keep

СВ131,

CR132,

CRi33,

and

CR135

conducting.

R2

and

Q5

share

the

load

current

to

reduce

the

dissipation

іп

Q6.

For

small

load

currents

Q5

is

turned

off

and

resistor

R2

supplies

the

current.

As

the

load

current

increases,the

base

of

Q5

is

forward

biased

and

Q5

conducts,

sharing

the

current,

As

the

load

current

is

increased

further,

CR134

is

forward

biased

at

a

current

level

determined

by

R159.

This

will

reduce

the

current

in

СВ135

to

zero

causing

the

supply

voitage

to

go

to

zero

also,

4-29.

PLUS

34

VOLT

SUPPLY.

4-30.

The

+34

volt

supply

provides

regulated

voltage

to

the

power

amplifier

circuits.

Breakdown

diode

CR143

establishes

the

reference

at

the

base

of

Q8.

Potentiometer

R163

adjusts

the

current

limit

setting

for

the

+34

volt

supply.

4-31.

REFERENCE

SUPPLY.

4-32.

The

diode

regulated

reference

supply

(refer

to

Figure

5-14)provides

+7,

-7,

+15

and

-15

voltages.

Capacitors

C126

and

C128

filter

the

ac

voltages.

Breakdown

diodes

CR146

and

CR147

maintain

a

+15

reference

voltage

at

the

junction

of

R149

and

R150.

The

series

arrangement

of

diodes

CR120

and

СВ121

(forward

biased

diodes)

and

СВ122

and

CR123

(re-

verse

biased

diodes)

compensates

for

temperature

and

provides

a

constant

-15

reference

voltage

at

the

junction

of

В151

апа

R152.

The

plus

and

minus

7

volt

reference

voltages

are

obtained

in

the

same

manner

as

the

plus

and

minus

15

reference

voltages.

Series

regulator

Q111

provides

regulated

+30

volts

to

the

positive

side

of

the

reference

supply.

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