Chevrolet 985447 Radio Service And Shop Manual

CHEVR.OLET

R.ADIO

SER,VICE

AND

SHOP

MANUAT

985432-PUSH

BUTTON

RADIO

985455-CHEVY

II PUSH

BUTTON RADIO

98543r

-MANUAT

RADTO

985453-CHEVY II I/IANUAL RADIO

985449-COR,VAIR

PUSH

BUTTON

RADIO

985447-CORVAIR

MANUAT RADIO

98539ó-CORVETTE

RADTO

985471-fnANUAt

TRUCK RADTO

985443-SERIES 95 MANUAT

TRUCK RADIO

98551 9-GUIDE.MATIC

HEADLAÍNP

CONTROL

FOR

I I6

3

FOR,EWOR.D

The

informqlion in lhis

service ond shop mqnuql

covers o

generol

description

of

Chevrolet Rqdios

qnd

Guide-Mqtic

Heodlomp

Control

for l9ó3

qnd

thorough

doto on operolions,

specificolions and

procedures

for lesling

ond

servicing

Chevrolet

Rodios

qnd

Guide-Mqtic

Heodlomp

Control.

CHEVROIET

MOTOR

DIVISION

GENERAT

MOTORS

CORPORATION

DETROIT 2, MICHIGAN

Copyr¡ght

I

9ó2

Chevrolet

Motor Division

Generol Molors Corporotion

ffi

Litho

in U,S,A¡

P&A

l9ó3

8.5M

INDEX

GENERAL

INFORMATION

-

ALL

MODELS

Electrical

DescriPtion

Procedure

for Checking

Inoperative

or

Noisy Radios

Procedure

for

Checking

and Servicing

Printed

Circuits

Procedure

for Checking

Transistors

Service

Procedure

for the

Push Button

and

Manual

Radios

Procedure

for Servicing

the Corvette

Radio

Procedure

for

Alignment

of AII Chevrolet

Radios

Capacity

and Inductance

Alignment

Procedure

for All Chevrolet

Radios.

985432

PUSH

BUTTON

RADIO

General

Information

Transistor

Complement

and Function.

.

Page

1

2

5

I

L2

13

Push Button

Setting

t4

14

16

18

t7

19

15

Condensed

MechanicaL

Operation

of

the

Push

Button

T\rner

Mechanical

Adjustment

of

Tuner

Procedure

for

Parts

Replacements

Radio

Circuit

Diagram

(Schematic

Drawing)

Service

Parts

List

Troubleshooting

the

Push Button

Radio

985431

MANUAL

RADIO

General

Information

Transistor

Complement

and

Function

.

. .

.

Circuit

Diagram

(Schematic

Drawing)

Service

Parts

List

Procedure

for

Part

Replacement.

. .

.

Troubleshooting

the

Manual

Radio

. . .

985449-985455

DELIIXE

PUSH

BUTTON

RADIOS

FOR CORVAIR

&

CHEVY

II

General Information

Transistor Complement

and

Function.

.

Push Button Setting

.

Condensed

Mechanical

Operation

of

the

Push

Button

T\rner

and

Radios

Tuner

Adjustments

for

985449

-

985455

Radios

Circuit

Diagram

(Schematic

Drawing)

Service

Parts

List

Procedure

for

Part RePlacement

Troubleshooting

the

Push

Button

Radio

98544?-985453

MANUAL

RADIOS

FOR CORVAIR

&

CHEVY

TI

General

Information

Transistor

Complement

and

Function.

Circuit

Diagram

(Schematic

Drawing).

Service

Parts

List

.

. .

.

Troubleshooting

the

Manual

Radio

. . . .

2t

2l

22

2l

2L

22

2t

27

28

31

29

33

31

28

38

40

38

46

General Information

985396 CORVETTE

RADIO

985396

CORVETTE

RADIO

(Cont'a.

)

Tube

and Transistor

Complement and Function

Push

Button

Setting

Operation of

the

Wonder Bar Tuner

Mechanical

Adjustment

Procedure

for

Part

Replacement. . .

Circuit Diagram

(Schematic

Drawing).

Service Parts

List

Troubleshooting

the

Wonder Bar

Radio.

985471

TRUCK

RADIO

General

Information

Transistor

Complement and Function.

.

Circuit

Diagram

(Schematic

Drawing).

. . .

Service

Parts

List

Troubleshooting

the Manual

Radio

985443

SERIES

95 TRUCK

RADIO

General

Information. .

Transistor

Complement

and Function.

.

Circuit

Diagram

(Schematic

Drawing).

Service Parts

List

Troubleshooting

the Manual

Radio

985519

GUIDE-MATIC

HEADLAMP

CONTROL

Adjustments

and Tests

General

Description

Circuit Diagram

(Schematic

Drawing)

Functional

Operation

Sensitivity

Tests

Service

Parts

List

.

Trouble

Shooting

Procedure

Vertical

Aim. .

Page

46

47

51

52

55

66

68

67

66

60

59

63

60

59

74

73

78

74

76

79

74

?6

CHEVROLET

RADIO

SERVICE

AND SHOP

MANUAL

Electrical

DescriPtion

The

circuit

used

in

the

Chevrolet

receivers

are

of

the

superheterodyne

type

that

use

no regenera-

tion.

The tuning

circuits

are

of

the

permeability

type and

are

tuned

by varying

iron

cores in and

out

of

the antenna,

radio

frequency, andoscillator

coils

like

pistons. This

is shown

for the

push

button

models

in

Figure 1.

Figure I

The

intermediate

frèquency stages are

tuned by

means

of two

iron cores in

each

transformer

as shown

in

Figure 2,

and are adjusted

from the

top and

bottom

of

the transformer.

Both

the

first

(input)

and

second

(output)

intermediate

frequency transformers are

tuned

bythis method.

Figure

2

The

antenna

circuit

is

coupled to

the antenna

by

means of an adjustable

antenna

trimmer

to take

care

of

normal

variations

in

antenna

and

antenna

cable

capacity.

The

antenna

trimmer

is

located

on the

front of the radio

chassis

under

the

dummy knob on

the manual

tuning shaft, and

is

adjusted

by means

of

a small screwdriver.

This

trimmer

permits

the receiver to be ad-

justed

to

any of

the Chevrolet

antennas

for

maximum

sensitivity

and

performance.

This

adjustment

is

very

important, and

station

mixing

may occur if

it

is

not

adjusted.

Procedure For Checking

Inoperative

Or

Noisy

Radios

Receiver

Completely

Dead

Check

for a

blown

fuse,

blown

fuse could

be

caused

by one

of the

foliowing:

1.

Short

in

12

volt

circuit

of

radio.

It

will

be

necessary to

remove

radio

from carandcheck

the

12

volt

circuit.

2.

Solenoid

remaining energized.

(Wonder

Bar

Radio

only).

Check

speaker

for open circuit.

Check antenna

for

open

or short

circuit.

Weak

-

No

Volume

A

weak

receiver can be

caused by

the

failure

to

adjust

the antenna

trimmer

or the speaker

not

being

completely

plugged

in.

Check

these before

removing

the radio

for

servicing.

IMPORTANT:

Adjusting

the

antenna

trimmer

for

maximum

volume

on a weak

station

or

noise

will

provide

maximum

performance

and

prevent

weak

& fading

radios.

Figure 3

To

prevent

weak

or fading reception,

remove

right-hand tuning

knob

and

adjust

"Antenna

Trimmer"

screw.

See sticker

on radio

for

instructions.

CAUTION:

THIS

\VILL

NOTWORK

IF TUNED

TO A STRONG STATION.

1

NOISY OPERATING

RADIOS

The noise can be

caused by

one

or more

of

the

following:

1.

TIRE

STATIC is

caused by

friction

between

the

tires and

pavement,

and

is

almost a

continuous

roar

while

car

is in

motion, and

does

not

vary

appreciably

with

car speed.

The

intensity

of

the noise is

greater

on

a

dry

sunshiny day, and

not

so

noticeable on

humid or

rainy days.

To

eliminate

this type

noise be sure

that

the

front wheel static

collectors

have been installed,

being sure that

they are

free of

grease

and are

making

good

contact

to

front

wheel

spindle.

If

the static

still

persists,

install

tire static

powder

in

all five

tires.

2.

NOISY ANTENNA can be located

by

turning

on the radio

receiver,

tuning in a station

and

by

tapping the antenna with

a

scre!'¡/ driver

handle.

If

noisy,

a

crashing sound

will

be

heard

in

the

radio each

time

you

tap

the

antenna.

The

antenna

lead-in can also

cause

noise

in

the radio if

the shield

is broken

or

unsoldered

from the ends,

or if the

lead-in

r¡¡ire in cable is loose or

broken.

This

can be

checked by shaking

the

antenna

lead-in

cable.

If

you

can cause a

crash in

the radio while

shaking

lead-in,

replace

lead-in.

3. MOTOR INTERFERENCE in

Chevrolet

radios

is usually

caused by

poor grounds

when

in-

stalling

the

antenna

or receiver.

Check

to

make sure all

required suppression

material

has been installed and

that aII

grounds

are

free

of

paint,

grease,

or rust and

are

tight.

4. GENERATOR

INTERFERENCE is a whining

noise similar

to

a

siren,

and

increases

or

decreases with speed

of the engine.

InstaII

or replace

generator

condenser.

5.

Delcotron Interference is

a

whining

noise

most

noticeable

with

the radio volume

very

Iow.

This noise

is usually

caused

by a defect

in the

Delcotron

itself.

However,

in the

radio

it is

necessary

to

keep

the

"4"

lead

(battery

input) away

from other

leads

which

would

pick

up

noise,

particularily the

volume control

leads.

Procedure

For Checking and

Servicing

Printed

Circuits

Atl

stages of the

1963 Chevrolet

radios

use

printed

circuit boards, the

latest method

used in

wiring electronic

products.

The

printed

circuits

reduce

the

possibilities

of

shorted

or broken

wires

and

loose

connections that

the

wired

sets

were

subject

to.

The

servicing

of

printed

sircuits

is

not

difficult

but

a

few

precautions

must

be

observed when

trouble develops

in

the component

parts

mounted

to

the

printed

circuit board

and

repairs

or re-

placements

are

made.

In the

servicing

of the

printed circuit

portion

of

the

radio, EXCESSIVE

HEAT

applied

toanyof

the

soldered

terminals

can cause

the

printed

circuit

to

lift from the

circuit board

which

results

in

the

necessity

of replacing

the

entire

printed

cir-

cuit

board.

A

25

to 50 Watt

soldering

iron is

recommended

for

work

on

the

printed circuit

board.

Care

should be taken

not

to

place

the

soldering

iron

tip

directly

on

the

printed circuit

board.

The iron should

be

placed

on

the

lead or

terminal

being soldered to the

printed

circuit

which will

allow

the heat

and solder

to

flow

down

the lead

or terminal

to the

printed

circuit.

When

removing or

replacing component

parts

mounted

on the

printed

circuit board,

it

is im-

portant

that

the

heat be applied

to the wire

lead

or terminal

and

not directly to

the

printed

cir-

cuit.

A

small wire

brush

is most

helpful

in

the removing

operation.

Care shouldbe

exercised

not to crack

or break

the circuit

board as any

break in the board will

necessitate

replacement

of

the

circuit

board.

The

printed

circuit has an insulating

and

sealing

coat

placed

over

the

entire

board after

the cir-

cuits are

put

in

place

on the board,

and

for

any soldering

that

is required

on the

printed

stripes,

the insulation must

bescrapedoff

-

NOT

BURNED

OFF

with

a soldering

iron as

it

wiII

also burn

the

printed

strip.

If

a

portion

of

the

circuit on the

board

is broken,

it can

be repaired

by scraping

off the insulating

coating

and

solder-

ing a

piece

of wire

across

the break.

Resistance

and

at

the soldered

any soldering

make sure

to

solder

from the

voltage

reading should

be made

point

on the

circuit board.

After

operation

has been

performed,

remove

any

loose

particies

of

printed

circuit

board.

Procedure

For

Checking

Transistors

Transistors have

a very

low failure rate,

how-

ever, they do

fail

occasionally

so

a

transistor

checking

procedure

is very valuable.

The

transistor

which

is most

likely

to fail is

the large

power

transistor

called

the output

transistor.

This

coutd

cause

no

"Thump"

to be

heard as

the radio is

turned on, but

remember

that

a defective speaker

or blown

fuse

will also

prevent

the

t'Thump".

2

DOT

BY

ùs-221

D6-24

LTRANSISTOR

DS-25 I

renmlraus

6-

26J

COLLECTOR

(SERVICE

TRANSISTORS

ONLYI

&

I-OOATING

LUG

BASE

TERMINAL

EMITTER

LEAD

INAL

OR BASE

TERMINAL

-BASE

YELLOW

LEAD

OR

BASE

TER

-EMITTER

ooLl-EoTo

rs cAsE

ÍvIOUNTING

STUD

OOLLECTOR

Dg-5O3

TRANSISTOR

TERMINALS

DS€OI

TRAT.ISISTOR

TERMINALS

Figure

4

There

are many

co.mmercial transistor

checkers

on the market also

newer type tube

checkers

can test

transistors.

These

checkers

have their

own testing

procedure

so

the followingparagraphs

wilt be devoted

to testing

transistor with

an

ohmmeter.

Checking

Power

Transistors

The

DS-501

and

DS-503

leads

must

be unsoldered

and

disconnected

from

the

circuit.

Allow

the

transistor

to cool

to room temperature

before

checking.

Place

an ohmmeter

on the

Rx1

scale

and

"zero"

the

meter.

Connect meter

between

the

emitter

tead

and

the

cotlector mounting

stud,

see

Figure

4 leaving the

base open.

After

taking

this

read-

ing, reverse

the meter

leads

and

read the

meter

again.

The

lowest

of these

two readings

must

not

be belorv

50 ohms.

If

the

transistor does

not read

S0ohmsor

higher,

the transistor is defective

and should

be re-

placed.

Most

defective

power

transistors

read

'(O"

ohms.

This

will

cause

the fuse

resistor

on the

circuit

board

to open and

often

causes

the

10

ohm

resistor

connected

to the

fuse

resistor

to

increase

in value,

These

must

be checked

and

replaced

if

necessary.

Checking

Small Transistors

SmaII

transistors,

such

as

the

D522,

DS24,

DS25,

and

DS26 usually open

inside

the

transistor

when

they fail.

When this

happens,

no signal

can

pass

through

that stage.

If

a

stage

is

found to be

dead

by the signal

injection

or

"Trouble

Isolation"

procedure,

the

transistor

can

be checked

by

bridging a

good

one

across it,

just

like

an

open

condenser

is

checked:

1.

Connect a

good

transistor

of

the same

or

equivalent

type across

the

one in

the

circuit,

make

sure

that all

three

leads

are

making

a

good

connection

at

the

proper

solder

points

on the

circuit

board

-

Base

lead

to

point

B;

Emitter lead

to

point

E; Collector

lead

to

point

C. See

Figure

5.

2. IL

the

radio

plays,

remove

the

defective

transistor

from

the

circuit

and

solder

the

new

one

in.

3.

If

the

radio doesn't

play,

the

something

else

is at

fault.

Go

cedure

for

Trouble Isolation".

chances

are

to

the

"Pro-

NOTE:

The

above

test

cannot

be

made

on

the

large

transistors,

DS501 and

DS503,

because

they

usually

short

instead

of open.

3

\

OIRCUIT

BOARD

o

c

*r.oïI?3ro'

OHMMETER

TEST

Small transistors

can

also

be

checked

for open

Ieads

by

using

an

ohmmeter.

However,

different

meters

give

different

readings,

depending

on

the

range sélected,

the

battery

used

inside,

and

the

meter

resistance.

The

table

in

Figure

6

shows

the

readings

ob-

tained

when

a

Simpson

Model

260

Volt-Ohm-

Milliameter'

or

RCA

Model

1VV-??A

was

used'

The

procedure

is:

1. Set

the

meter

on

the

RX100

range

(radio

power

suPPIY

off).

2. Connect

the

ohmmeter

leads

to

the

Base and

Emitter,

B

and

E,

solder

points on

the

cir-

cuit

board.

Now

reverse

the

meter

leads

and

connect

again

to

B

and

E'

A definite

change,in

resistance

should

be

noted,

and

one

of

the

readings should

be

less

than

500 ohms'

3.

Connect

the

ohmmeter

leads

to

the

Base

and

Collector,

B

and

C, solder

points on

the

cir-

cuit

board.

Now reverse

the

meter

leads

and

connect

again

to

B

and

C'

A definite

change

in

resistance

should

be

noted,

and

one

of

thã

readings

should

be

less

than

500 ohms'

NOTE:

In

Figure

6

that

the

power

to

the

radio

must

be

turned

off,

and

the

radio

vol-

ume

control

turned

completely

clockwise

be-

fore

taking

ohmmeter

readings.

NOTE:

That

the

DS22

and

DS26

have

a

5:1

ratio

or

better

when

the

highreadingisdivided

by

the

low

reading.

The

DS24 and

DS25

have

a

10:1

ratio

or

better.

If

the

transistor

is

removed

from

the

circuit

and

tested,

the

low

readings

will

be about

the

same

as

shown

in

the

chárt,

but

the

reversed

readings

will

be

much

higher.

NOTE:

Adequate

tests

are

provided

to

de-

termine

if

transistors

are

functioning

prop-

erly.

It

is

not

necessary

to

remove

and

"eplace

transistors

that

have

passed

these

te sts.

Figure

5

Figure

ó

4

IN-CIRCUITTESTINGoFSMALLTRANSISToRSUSINGoHMMETER

Radio

Power

"Off",

Volume

Control

Set

at

Maximum

Meter

Scale

RX100

Values

may

vary

with

different

meters.

Above

measurements

were

made

with

a Simpson

Model

260

or

RCA

Modet

WV-774

meter'

**Reading

will

be

lower

if volume

control

not

turned

completely

clockwise.

Transistor

Meter

Reversed

BandC

Meter

on

BandC

Meter

on

BandE

Meter

Reversed

BandE

DS22

DS24

DS25

DS26

250

Ohms

250 Ohms

200

Ohms

200

Ohms

1,900

Ohms

50,000

Ohms

?,000

ohms

2,000

Ohms

200

Ohms

200

Ohms

200

Ohms

200

Ohms

2,000

Ohms

50,000

Ohms

3,000

Ohms

**1,500

Ohms

Service

Procedure

For

The

Push

Button

and

Manual

Radios

Turn

on signal

generator

and

set

in

audio

posi-

tion to

obtain

a

400 cycle

audio

signal.

Ground

one

lead

of

signal

generator

to

radio

chassis.

A

.1

mfd,

capacitor

should

be

placed

in series

with

the

remaining

lead to block

D.C.

current,

The

lead with

the capacitor will

be

the

probe

for

signal

tracing.

Keep radio volume

controlturned

to maximum

for

all

tests.

PRELIMINARY TEST

(IMPORTANT) -

Turn radio

on

with

ear

next to speaker.

As

this

is done a

"thump"

should

be heard

in the

speaker.

If

O.K.

go

to Step

1. If no

"thump"

was

heard,

check:

a.

Speaker connections and

speaker

for

proper

hook up.

b.

Power connections and

fuse

for

proper

hook

up.

c.

DS501

power

transistor

collector voltage

by

measuring

the voltage

between

the transistor

case

and

chassis.

(IMPORTANT:

DO NOT

CONNECT

METER,TO

THE

TRANSISTOR

HEAT SINK

OR FINS.)

d.

A

reading of about

11

volts

from

collector

to

ground

means that something

is

open between

collector

and

ground.

Check output

trans-

former.

Note

of

Explanation:

The

signal

generator

is

now

put

into use, beginning

with

Step

1.

The

letters

in

parenthesis

are

found

printed

on

the

circuit board.

For example,

(AF)

stands

for

"Audio

Frequency"

amplifier

and

refers

to the

DS26

transistor.

(C)

stands

for collector.

When

the signal

generator

is applied at

thrat

point,

if

nothing is heard the output

stage

should

be

re-

checked

as

described

in

the

preliminary

test

above.

The

test

points -

Step

1

through

Step

7

-

are

shown in

Figure

7.

STEP 1.

Touch

generator

probe

to

DS26

(AF.)

collector

(C)

anA

adjust

generator

output

to

pro-

duce

weak

tone.

If

weak

tone

cannot

be

heard,

check the

DS501

output

stage.

Without

changing

generator

controls,

go

to

Step

2.

STEP 2.

Apply

generator probe

to

DS26

(AF)

base terminal

(B).

An

increase

in signal should

be noted, indicating

DS26

transistor

gain. If

O.K.

go

to

Step 3.

If no

gain

was

heard,

check:

a.

DS26

transistor

without

removing

it

from

the

circuit.

See

"Procedure

for

Checking

Small

Transistors"

page

3. Volume

control

must

be

completeiy

clockwise during

all tests.

b. Check the voltage

at

the

DS26(AF)

collector

(C),

by

measuring

between

(C)

and chassis.

The

voltage

should

be about

.5 volt.

A

read-

ing of

"0"

volts or

near

tt0"

means

that

no

current is

flowing

in this stage, and

one

of

the

following items

is

probably

defective:

Open

resistor or

poor

connection

in

the

Base

(B)

circuit,

or in

the

Emitter

(E)

circuit.

Trace

the

printed

circuit

from those

points

and

check

for open solder

connections.

c.

A

very

high

voltage

of

10 or

11

volts

from

DS26

(AF')

collector

(C)

to

ground

means

that

there is an

open

between

collector and

ground.

Check

input transformer

resistance,

andcheck

for bad solder connections.

d. Bridge a

100 mfd.

capacitor

across

item

33.

If the

gain

comes up,

replace

the

capacitor.

Change

signal

generator

from audio

position

to

generate

an intermediate

frequency

signal.

Set

signal

generator

lo

262 kilocycles.

STEP

3.

Apply

generator

probe

to base

(B)

of

DS22

(IF)

transistor.

A

loud

signal

should

be

heard

without

turning

the

generator controls

to

a very

high level.

This

usually

takes

less

than

half the

maximum settings

on

the signal

gen-

erator,

as

wiil

be

learned

by

practicing

with

your generator

on

a

good

radio.

If O.K.

go

to

Step

4. If

no

signal

or a

very weak

signal

is

heard,

check:

a.

DS22

transistor without

removing

it

from the

circuit.

See

"Procedure

for

Checking

Tran-

sistors".

b. Voltage

between collector

(C)andgroundinthe

DS22

(IF)

stage.

Shoutd

be

"0"

volts.

If

voltage

.is

high,

near

10 or

11

volts,

the

trouble

is due to:

Open

connection

in

the

(IF)

collector circuit

(C),

or open

IF

transformer,

item

6.

c. Check

DS22

(IF)

conduction

by measuring

voltage

across

the

1000

ohm

resistor,

item

54.

Measure this

by

putting

the

positive

Iead

of

a

d.c. voltmeter

on

conductor

2

on

the

circuit

board, and

the

negative

lead

on

the

emitter

(E)

of the

DS22

(IF)

transistor.

The

voltage

should

read

about

1.0

volt.

If the

voltage

is low

or

near

"0",

check

for:

Open connection

on

the

circuit

board

in

the

5

\

SIGNAL

GENERATOR

fU NI NG

o\

v OL !'

N'F

aft

FREOUEl{CY

fONE

aFlWÉEN.5

ô

I

AUDIO

FqEOUE^¡CI

A

STEP

BAND

--

ouTPUf

lo @

o

ol

l¡uo'o-tx

¡lr-q.r

-t¡

J

ac

\

D

output

coñfRoi

STEP

gTEP

WEAK

OR

NO SIGNAL

fONE

B

C

VOLUME

BEIWÉEN.5

I

¡uDro

rnEouEt¡cv

a-.-

u

ourput

co¡tnou

EANO

_OUTPUT

lo @

o

ol

louoro-¡r

¡rr

-

n.r

-

t.¿

J

SIGNAL

GENERATOR

ON

off

U¡MOOIJLAIEO

fUNING

FREOUENCY

EAND

-oUTPUf

-

lo @

o

@l

louoro-¡x

¡rt-

n.F.

-

r.Ê

J

D

output

oo¡.¡fnoL

fUNING

MODULAfEO\

ON

oFf

VOLUME

FETWEEN

A

FREOUÉNCY

SIGNAL

GENERATOR

FREOUÉNCY

fONE BC

7

6

5

4

3

I

z

F

E

c

A

o

@

Figure

7

STGNAL

TRACTNG

LOCATIONS

ON

CIRCUIT

BOARD -

ALL PUSH

BUTTON

AND

MANUAL

RADIOS

(IF)

base

circuit

(B)

or emitter

circuit

(E)'

Check

IF

transformer'

item

5,

for open.

If

the

voltage

is

very

high

instead

of

"0",

check

for leakage

or

shorts

in

the

Base

(B)

anO

Emitter

(E)circuits,

including:

Shorted

.047

mfd.

condenser,

item

27.

Shorted.04?mfd.

condenser'

item

29. Shorted

IF transformer,

item

5.

d.

Bridge

a ,047

mfd.

capacitor

across

capacitors'

item

2?

and

item

29.

If

gain

increases,

the

capacitor

Paralleled

is

oPen.

e.

If

trouble

is still

not

located,

turn signal

generator

volume

control

to

maximum.

Apply

it

collector

(C)

of

DS22

(IF)

transistor.

A

weak

signal

is

usually

heard,

depending

on

the

signal

generator.

If no signal

is

heard,

check

or replace:

I.F.

transformer'

item

6; detector

diode

DS27.

STEP

4.

Appty

generator

probe

to

DS25 con-

verter

collector

(C)

and

adjust

generator

output

to

produce

weak

tone.

Without

changing

gen-

erator

controls,

go

to

SteP

5.

STEP

5.

Apply

generator

probe to base

(B)

of

DS25 converter

transistor.

An

increase

insignal

should

be

noted,

indicating

DS25 transistor

gain.

If

gain

is

not

present, check:

a.

DS25

without

removing

it

from

the

circuit.

See

"Procedure

for

Checking

Small

Tran-

sistors".

b. Vottage

between

collector

(C)

and

ground in

the

DS25

converter

stage.

Should

be

rr0"

volts.

If

voltage

is

high,

near

10 or

11

volts'

the

trouble

is

due

to

one

of

the

foilowing:

Open

connection

in the

collector

(C)

circuit

in the

converter

stage.

OpenIF

transformer,

item

5.

Open oscíllator

coil,

item

4.

6

m-.e::-"ilÞ]

SIGNAL GENERAIOR

o

ourrur co¡trcu

luNlNc

ac

&ND

fÂEOUENCY

roNt

oro'o

r¡¡ouENct

a

m-å::::þlr

SIGNAL GEN€RAÍOR

o

outrut otrcu

ÌUNIN6

FÊEOUENCI

ac

&ND

fotE

ÎONE

A C

V4UME

Âuoro

FiFqu€Ncl

Â o

oulPur coilrrcL

SND

f-

oulPuf -------l

lo o o ol

l¡o'o-¡¡

¡tr-¡¡

-r¡

J

SIGNAL GENERAIOR

0s

503

OUfPUf

I, E AMP

{sñvrcE

wrfH

os25l

os 22

r¡

L!

I

o

R.Ê AÍP

lsñvrcE

wrtH 6251

2C

DS 24

I

J

621

A6

o€f

os

25

Ds

!è

r--

MEô

I

fRot

fusÊ

alæx

650

Figure

8

SIGNAL

TRACING

PROCEDURE -

985432 -

RADIO

c. Check

DS25

converter

conductionby

measuring

voltage

across

the

3900

ohm

resistor,

item

51.

Measure this by

putting

the

positive

lead

of a

d.c.

voltmeter

on

conductor

2 of the

circuit

board, and

the negative

lead

on the

emitter

(E)

of

the

DS25

converter.

Thevoltageshouldread

about

1.0

volt.

If

the voltage

is

low or

near

"0",

check

for:

Open connection

on

the

circuit

board in

the

converter base

circuit

(B)

or emitter

circuit

(E).

If

the voltage is

high, about

10

or

11

volts'

check for: Shorted .000220

condenser'

item

25. Shorted

.0047 condenser,

item

24.

Shorted

trimmer, item

218.

d. If

alt

above

tests

pass,

align

lst

I.F. coil.

If

coil

fails to

peak

sharply

replace

it.

See

alignment

procedure.

Change

signal

generator

from

intermediate

fre-

quency

setting

to

radio

frequency

signal.

Re-

move

the .1

mfd. condenser

from

the

probe

lead

of the

signal

generator.

Place

a.000082

mfd.

con-

denser

in

place

of

the .1

mfd.

just

removed.

Set

signal

generator

to

1100 kilocycles

and

tune

radio receiver

to

1100 kilocycles

(11

on

dial

scale).

A

slight

retuning

of

the

radio

dial

may

be

necessary,

once

the

signal

is

injected

into

the radio,

to

provide

maximum

signal

through

the

radio.

STEP

6.

Apply

the

generator

probe to

'DS24

(RF)

collector

(C),

and

adjust

generator

output

to

7

t

DS-50r

E

ro.8v. o

t.¡lv.

I

to.!v.

0s-26

c

ov.

DS-22

93V.

c

o5v.

B

DS-

24

I

0

ov.

DS-25

9.7V.

9.tv.

9.9V.

2.3V

B

to.4v

to.ov.

E

ro.ov.

Fisure

9 VOLTAGE

CHART -

ALL

PUSH

BUTTON

-

RADIOS

Fisure l0 PARTS LAYOUT

ON CIRCUIT

BOARD

'985432

-

RADIO

8

B

D

6

5

64

2tB

@

2t

4

t9

til

IJ

-

rl

nr

I

t¡ztT

lrl

1B-l

tfE

[46 II-l

#

27

tI

2l^

@

20

fE

f!! l

If

5s--l

:60 Iu

LFo

l

=

I

þr

@

E

FJ

lr

F

E

36

+

produce

weak

tone.

Without changing

generator

controls,

go

to

Step

7.

STEP

7.

Move the

generator

probe to

the an'

tenna

socket.

A

tone of equal

or slightly

less

volume

will

result

in the speaker.

If signal at

antenna

socket

is

not heard, check:

a.

DS24

transistor without

removing it

from

the

circuit.

See

"Procedure

for

Checking

Small

Transistors".

b.

Check

the

voltage

between

the coltector

(C)

and

ground

of the

DS24

(Rf')transistor.

Should

read about

2.3

volts d.c. with

antenna

dis-

connected

from the

radio.

If

voltage

is high, near

10

or

11

volts,

there

is an

open circuit

between

the collector

(C)

and

ground.

Check:

RF

coil, item 3,

and

resistor, item

47.

AIso

check

for

bad

solder connections

in

that

area.

If

voltage

is

low,

near

"O"

volts,

check:

Check

for opens in the

DS24

(RF)

base

circuit

(B)

and

emitter

circuit

(E).

Check the antenna

coil,

item

1, for

open.

Check

trimmer

capacitor, item

16

and

.0022

capacitor,

item

23 for short.

c.

If

(RF)

stage

is dead but voltages

areall

O.K,

check:

Antenna

coil,

item

1, for open.

There

are

two

windings

on this coil,

both at

rear of

tuner.

Check

antenna

choke,

item

2, for open.

Check

antenna

trimmer, item

16, for

short.

This

completes

the tests

for

a

weak

or dead

radio.

Below

are additional

hints

which

may

help

you

find the trouble

if it

has

not been

located:

If noise can be heard in the speaker

when

the

antenna

is

plugged

in, but

no

stations

can be

picked

up,

the converter

is

probably

not oscil-

Iating.

To

check

for normal oscillation,

mea-

sure the voltage across

the 3.9K

resistor,

item

51

should

be about

1.0

volt.

Tune the radio

from

one end of the

dial to the other while

watching

this

voltage.

If

the voltage

does

not

change

slightly, the converter

is

not osciilating.

Common

causes of this are:

Open

condensers

in

the

DS25 converter

circuit.

Check

by

bridging them with

good

capacitors

of

the

same value.

Open

oscillator coil, item 4.

Defective

trimmer, item

21.

If

the radio

plays

loudly

but is

muffled on very

strong stations,

check the

voltage between

(RF)

collector

(C)

and

ground.

This

voltage

should

drop to a

low value when

turned

to

a strong

station.

If it doesn't,

check:

DS27 AGC

diodes,

item

201

and

item

202.

When

checked on

the

RX100

scale

of an

ohmmeter,

there should be

10:1 ratio or

better.

Also check

to

see

that those

diodes

are

not mounted

back-

ward.

Check for open in

conductors

22-36

and

39.

If the radio is very weak

and

distorted when

tuned to strong stations,

check:

a.

The

speaker

and

connections.

b,

,47 ohm

or'

.33

ohm

fuse resistor,

item

64,

for open.

Check

the clear

mica insulator

between

the

power

transistor and

the

heat

sink

or

fin.

The fin

is

grounded

to the radio

chassis

on

some models,

but

transistor

is insulated

from

the

fin by

an

almost

invisible

piece

of

mica.

Other models

have the

fin insulated

from the

radio and the

transistor

connected

directly

to

the

fin.

Procedure

For

Servicing

The

Corvette

Radio

All

circuits, except

the trigger

circuit, are very

similiar

to the

push-button

and

manualreceivers,

so

the troubleshooting

procedures

outlined

for

these sets may

be used

for the wonder

bar

radio.

Figure 10

shows

the schematic

diagram

for

the Corvette

radio and

the

various

points

of

signal injection.

It

is very important

that the

first three stages

of the

radio are

working

and

aligned

properly

before any attempt

is

made to

troubleshoot

the

trigger circuit.

CONDENSED

ELECTRICAL

OPERATION

OF ELECTRICAL

TUNER USED

ON

ÍWONDER

BAR RADIO

.

985396

The

purpose

of

the electrical

components asso-

ciated

with

the tuner

is

to control

the relay

so

the operator

may start

the tuner sweeping

cycle

by

merely

depressing

a station

selector

bar

switch

so

that

the sweeping

operation will

con-

tinue until

a signal

is

received.

At

that

time' it

I

Defective DS25

transistor.

_OUÍPUT_

lo @ o ol

¡¡uo,o-¡x

¡rr

-¡

r _r ¡ I

SIGNAL

GENERATOR

BC

¡qEouÉtcv

Âa

o

oulput coilt&L

&N0

-oulPut-

lo o o rl

rÀ@'o-rx.ÀNÌ-rr

-,.

-J

SIGNAL

GENERAÎOR

TON€

BC

Âuoro

FREouENcY

À

D

ourpur co¡rrcr

MflO

-ourPul

-

lo o o ol

r¡uo'o-¡¡

¡rr

-¡¡

-,

¡ I

SIGNAL

GENËRÂÍOR

ac

fONE

lsRvrcE wtTH

oszat

DS

22

0s 50r

OUIPUI

I

)

(4

,l

)

(3,

ì

428

LO

(

,Zá

gRVtCE

W¡fH

625)

ç

.oooo82

DS 24

627

0El

DS

25

coNv.

os 26

to

ea

El-

ro ,,se

þffi"

Fisure

ll

-

SIGNAL

TRACTNG

PROCEDURE

-

98539ó

_

RADTO

is

the

function

of this

circuit

to

accurately

tune

to

the frequency

of

the

selected

station.

It

also

provides

the necessary

conditions

to

keep

the

tuner

on

the

station

until

a

change

is

desired.

ELECTRICAL

OPERATION

CYCLE

1.

To

start

the

tuner,

the

station

selector

bar is

momentarily

depressed

actuating

the

station

selector

switch No.

89

which energizes

the

relay.

A.

Switch

No.

89

completes

a

circuit

from

ground

through

the

station

selector

switch

(89)

and relay

(84)

to

the 12

vott

suppty.

B.

The

current

through

this

circuit

energizes

the relay

(84)

and

removes

the

relay

arm

from

the

stopping

disc

-

thus

starting

the

tuner,

and opening

contact

No.

2andclosing

contact

No.

1

on

the

relay

switch

(84).

2.

To

keep

the

tuner

seeking

after

the

station

selector

bar

is released,

the relay

is held

energized

by

a

holding

circuit.

A.

Contact

No.

1

being

closed

supplies

voltage

to

3 of

the 124L8

tube

which

causes

plate

current

through

the

relay.

3. To

stop the

tuner

on

station,

the relay

is

de-energized

by

an electronic

triggering

cir-

cuit

actuated

by

an incoming

signal.

10

680K

zND

I.E

sEc.

2ND ¡F

sEc

28.

-l

os

zND ¡.E

PRIM

.oooroo

2

VOLÎS

84

86

I2AL8

TRIGGER

ß

55

56

PUSH

BAR

GIRCUIT

89

90

30

SENS.

CONTROL

R.F, STAGE

A. The

incoming

signal develops a

voltage

in

the

primary

and secondary

of the

2nd I.F.

transformer.

B.

The I.F.

signal voltage

in

the

secondary

of the

2nd

I.F.

transformer is

coupled

through

the

condenser

(32)

to the

grid

of

the

trigger

detector

section

of the

124L8

tube.

This

signal voltage

is

developed

across

the resistors

(62)

and

(65).

C.

The

trigger

detector section

functions

as

a

plate

detector.

The

I.F.

voltage

appears

on the

grid

and

the

tube conducts.

The

I.F.

component is

removed in

the

plate

circuit

by the

.000100

condenser

(34).

D.

The

plate

current

flow in the

trigger de-

tector

section

develops

a

biasing

voltage

across

the

2.2

Meg.

grid

resistor

(?1),

making

the

grid

more negative

than the

cathode.

This

causes

the

plate

current in

the relay control

sectíon

to stop.

E.

Stopping

the current flow de-energizes

the

relay

(84)

and

the

relay

arm

engages

the

Fisure l2

-

TRIGGER CIRCUIT

-

98539ó

-

RADIO

stopping disc, stopping

the

tuner

onstation,

opening contact

No.

1, and closing

contact

No

2

of

the relay switch.

4.

To

hold the tuner on

the

new

station

until

another station

is desired,

the

relay is

held

de-energized

until the starting

circuit

is again

actuated by the

operator.

THE

TRIGGER

DETECTION

CIRCUIT

The

purpose

of

the trigger

detector

circuit is

to

take

the input

signal

voltages

of various

amplitudes

and

trigger the relay

tube so

that

the accuracy

will

be the same

on all stations

regardless

of

the

signal strength.

The

grid

of

the

plate

de-

tector

(trigger-detector)

is tied

into the

AGC

line.

A

portion

of the

AGC

voltage

is

used

to vary

the

bias on the

plate

detector

in

proportion to the

strength

of the

incoming

signal.

rüith

a

strong

incoming

signal,

the bias

voltage

is

high and

triggering doesn't

take

place

until

the

tuner

gets

very

near the resonant

frequency

of

the station

providing

the

incoming signal.

At

this

point

the

IF

signal

is

great

enough

to overcome

the bias

11

and the

plate

detector

is caused to conduct,

stopping the tuner.

Likewise

on a weak

incoming

signal, the

AGC

voltage

is small and the bias

on the

plate

detector

is

small,

therefore

a

smaller amount of

IF

signal

will

stop the tuner

at a

point

very

close to the

peak

of

the

in-

coming

signal. In

other

words,

the

AGC

voltage

raises

and

lowers

the

threshold over which the

IF

signal has

to

climb

in order

to

stop

the tuner.

The

circuit

is

so designed

that

the

IF

signai

voltage is high

enough to overcome the bias

and

stop the tuner

only

when

the tuner has

reached

the

station

frequency.

SENSITIVITY

CONTROL

The

sensitivity

control

g0

is a step

switch with

resistors

of

various

values between each

step.

The

control

is inserted

into the

AGC

circuit of

the RF

amplifier

during

the tuning

sweep

when

contact No.

I

of the

relay

switch is

closed" It

is

the means

by

which the

operator controls the

number

of

stations on

which

the

tuner

will

stop.

Typical

Complaints

and

Remedies

I. Tuner

stops

when

bar

is

released

A.

Check

or replace 124L8

trigger tube

B.

Check

or replace

relay

II. Tuner

runs

as

soon

as set is turned

on

A.

Check

for

a shorted foot

switch

B.

Check for

a short at the

wonder bar

selector switch

C.

Check for

a

sticking relay

III.

Tuner

will

not

stop on

stations

A.

Check

the

antenna and

124L8

tube. If

radio

is dead,

check

R.F.,

Conv,

and I.F.

Stages

B.

Ground

the negative

end or

a

1.5

V.

flash-

light battery

and

with

the

tuner cycling

touch,

the

positive

terminal

on

8

of

the 12AL8

tube. If

tuner

does

not

stop

check:

1. Capacitor

item 32.

2.

Capacitor

item 35.

3.

Associated

resistors

around

trigger

tube

4.

Check

or replace

relay

C.

With

a

VTVM,

check for the negative

AGC

voltage

on

8

of the

12ALB

tube

while

tuning

manually through

A

station.

Iï

no

voltage

appears

1.

Check AGC

system,

mainlyDS2?diodes

D.

With

VTVM,

check

for

the small negative

pulses

on

I

of

the

124L8

trigger tube

with the

tuner seeking.

If

no

pulses

are

present

-

1.

Check

sensitivity control circuit

2.

Align

2nd I.F.

coil

with a

meteracross

the

speaker

(I.F.

coil critical),

(always

replace

with

recommended

parts.)

IV.

Tuner

will

not

stop

on

the center of stations.

A.

Check

or replace

relay

84.

B.

Set the

clearance

of

the relay

when

ener-

gized,

so it barely

misses the teeth of

the

governor gear.

C. Align

the

2nd

I.F.

coil

and

replace

if it

does not

peak

sharply.

PROCEDURE

FOR

ALIGNMENT OF

ALL

CHEVROLET

RADIOS

All

receivers

are

properly

aligned

at

the factory

and should require

no further

adjustments, ex-

cept

adjusting the

receiver to

the antenna

when

installation

is

made unless the

adjustments

have

been

tampered

with,

or new

coils, intermediate

frequency

transformers

or tuning cores have

been

installed.

To

properly

align

the

receiver, it

will

be

neces-

sary to have

an

output

meter

and

signal

gener-

ator.

NOTE: If

any

one of the

tuning

coils or cores

have

been replaced,

see

"Capacity

and

In-

ductance

Alignment

Procedure"

before

pro-

ceeding

with

alignment

of

the receiver.

If

only the

adjustments

have

been

tampered

with

or an intermediate frequency

transformer has

been replaced, proceed

with the

alignment

as

follows:

1. First

hook

up

an

output

meter to the radio

receiver.

Any

volt meter

which will

read

"A.C."

can

be used. Set the volt meter

in

the 2.5

or

3 volt

"4.C."

range

position,

and

ground

one lead

of meter to

radio chassis.

Place

the other lead from

volt

meter on

the

speaker terminal.

t2

2.

Turn

on

signal

generator

and

set adjustments

to obtain

a

262 kilocycle

signal.

Connect

one

lead

of signat

generator to radio

chassis

for

ground. Attach the

other

lead

of signal

gen-

erator

to the base

of

the converter

transistor.

3.

Adjust

signal

generator

volume

control

so

that

the

volt

meter

will

tead

about

half scale.

NOTE:

Radio

receiver volume

control

must

be

turned

to the

maximum

position

so

that the

automatic

volume

control

circuit

will

not

affect

the

alignment

of the receiver.

4.

Adjust

in sequence

cores

"4,

B,

C and

D"

as

shown

on circuit

diagram and

parts lay-

out

for maximum

meter

reading.

Repeat

adjustments

to

get

maximum

meter

readings.

Keep the signal

generator

volume

turned

down

so

that during

adjustments

the

meter

does

not

read

more

than

half scale.

This

will

result

in a better alignment

of

the

re-

ceiver.

5.

signal

generator

setting

to

obtain

a

radio

frequency signal

and

tune

signal

generator

to exactly

1615 kilocycles.

Place a

.000082

mfd.

condenser

to antenna

connector

and

attach

signal

generator

lead.

Tune the

radio

receiver

to the

"Stop"

on

the

1600

kilocycle

end

of the

dial.

Keep the

signal

generator

volume

control

adjusted

so

that

output

meter

reads at

about

half scale.

6.

Adjust

trimmers

"E,

F

and

G",

on circuit

diagram and

parts

layout,

in sequence

for

'maximum

readings

on

output

meter.

Repeat

for maximum

meter

readings.

7. After the receiver

has been

installed

in

the

car, turn

on

receiver and

tune

in

a

weak

station

near

1000 kitocycles

with

the

radio

volume

control

turned

to maximum

position

and

the antenna

extended

to

full

height.

Re-

adjust

trimmer

'(G"

ONLY

for maximum

volume.

CAPACITY

AND

INDUCTANCE

ALIGNMENT

PROCEDURE

FOR

ALL CHEVROLET

RADIOS

This

alignment

procedure

is

to

be

used

only

when

any

of the

following

parts

have

been

re'

placed

in

the radio;

antenna

coil,

radio

fre-

quency

coil, oscillator

coil,

or any

of

the

tuning

cores.

The

intermediate

frequency

alignment

at

262

kilocycles is the same

as

outlined

in

"Al'ign

ment

Procedure"

operations

l through

4.

After

completing the intermediate

frequency

alignment,

proceed

as

follows:

1. Connect

signal

generator tead

to

a .000082

mfd.

condenser

and

connect

to antenna

termi-

nal of antenna

socket.

Mechanically

align

Figure

l3

iron

core

t'H",

on

circuit

diagram and

parts

Iayout

to measure

t-3f8"

for

aII

radios

ex-

cept

985396 and

it

is

1-5/8"

in coil

form

from

rear mounting

edge

of coil with

radio

tuned

to stop

on

1600 kitocycle

end

of dial.

2. With signal

generator

still

adjusted

to

exactly

1615

kilocycles,

adjust

trimmers

"E,

F

and

G" on

circuit

diagram

and

parts

layout

in

sequence

for maximum

output

meter

reading.

3.

Tune

signal

generator

and

radio

receiver

to

600

kilocycles

and

readjust

iron

cores

"J

and

K" ONLY,

for maximum

outPut

meter

reading.

Repeat

the

adjustment

for

maxi-

mum

meter

reading.

4.

Reset signal

generator to exactly

1615

kilo-

cycles

and

tune

radio

receiver

to

stop

on

1600

kilocyôle

end

of

the dial.

Then readjust

trimmers

"F

and

G"

ONLY,

until

no

further

increase

in

output

meter

reading

can

be

obtained.

5.

After the radio

receiver

has

been

installed

in

the

car,

turn

on

the receiver

and

tune

in

a

weak

station

near

1000

kilocycles,

with

radio

volume

turned

to maximum

position

and

an-

tenna

extended

to full

height.

Readjust

trimmer

"G"

ONLY,

for

maximum

volume.

13

CUSTOMER SERIES

95

TRUCK

RADIO

985443

The

radio consists

of

a

radio reciver unit

with

an

external

speaker. This

type

of

design is

Figure

ó8

advantageous for both

installation

and

service as

all

component

parts

of the receiver

are readily

accessible for

quick

efficient replacement

when

service

is required.

Using an external type

speaker

affords the advantage

of having a larger

type

speaker

in

a

limited

space area.

The

speaker

is coupled to the instrument

panel

by

a

special type

gasket,

thereby

using the

entire

instrument

panel

for

unusually

good

tone re-

production.

TRANSISTOR

COMPLEMENT

AND FUNCTION

DS.24

DS.z5

DS-22

DS-26

DS-503

Fisure

ó9

VOLTAGE

CHART

-

985443

-

RADTO

66

Radio Frequency

Amplifier

Converter

Intermediate

Frequency Ampiifier

Audio

driver

transistor

Audio

output

"HI-POWER"

transistor

GENERAL

INFORMATION

Tuning

range 540

-

1615

kilocycles

Intermediate

frequency

-

262

kilocycles

Maximum power

output

6

watts

Undistorted

power

output

3.5

watts

Current

drain

1.2

amperes at

12

volts

Speaker-Alnico

V

permanent

magnet

type

4" x

10,,

DS-503

lt.4v.

COLLECTOR IS

THE

CASE

Lrv

ll.2V

B DS-26

0

ov,

os-22

9.

o

o.5v

B

DS-24

B

c

DS-25

to.2

E

9.7V

E

9.9V

OV

9.5 V

E

to.4 v

c

2.3V.

B

ro.ov

E

ro.ov

fONE

B C

aFrwEEN,56t

\

ÂUOIO

FCEOUENCI

A

\

BAN

O

_OUÍPUT

lo o o ol

l¡uo,o-¡¡¡rr-n¡-'¡-J

SIGNAL GENERATOR

TUNING

o

output coNfRoL

F RÊOUEl'¡CY

o\

olf

vOLUfrIF

ï""iï^l¡

foNE

B

c

âEfwÊãN.5

A

I

¡uDto

ra¡ouÉ¡'¡cv

A-

m-a^"ii-:t:

SIGNAL GENERATOR

o

ourput co¡¡fnou

MOD!LAT€O\

IUNING

ON

oFf

vol-U t\rÉ

FREOUENCY

F-'Ji:::.e-el

SIGNAL

GENERATOR

o

ourput co¡,¡tnoL

ON

fUNING

VOLUME

off

FREOUENCY

fONE

ÊETWEÊN.5

ô I

¡UO.O

rCtOuEr,¡Cv

A

BC

5

7

3

4

I

2

c

E

F

A

o

SfEP

WEAK

OF

NO SIGNAL

STEP

Fisure 70 ISLAND

NUMBER

AND

SIGNAL

TRACING

OF CIRCUIT

BOARD

-

985443

RADIO

Voice

coil

impedance 10 ohms

at

400

cycles

AII

circuits use

a

printed

circuit board

Fuse

protection

2.5

amperes

SERVICE

PROCEDURE

Check

voltage

for

correct voltages

as shown

in

figure 67. If

voltages are

correct and

radio

does

not

play

proceed

as

outlined in

Service

Procedure

for

Push

Button

and

Manual

radios

on

page

5.

SERVICE

PARTS LIST

985443

-

RADrO

NOTE: Atl Chevrolet radio service

parts

are

available

to dealers

through

General

Motors Parts Division Warehouses.

Orders

for radio

parts

requirements

to be

placed

with warehouse

in the usual

manner.

Illus. Service

No. Part No.

1

2

3

4

5

6

7

?281 71 6

728t946

7282042

728L7L7

7282313

7282323

122t623

Description

ELECTRICAL PARTS

Coils

Antenna,

tuning

Choke, antenna

series

R.F., tuning

Oscillator,

tuning

1st

I. F.

2nd

I. F.

Choke,

12

volt

supply,

input

Capacitors

7271564

7282272

Spark

Plate

Electrolytic,

3

-

section

67

39

37

o,

æ

DS 24

R.F.

AMP

(s€RVTCE

Wrf

H 625)

os

25

coNv.

DS

22

I.

E AMP.

(SERVTCE

Wrf

H

OS25)

DS

26

A.F. AMP.

DS

503

OUT

PUT

A

r---

3V

57

MEG.

O!

to

2v

6A

t2v.

ç

FROM

FUSE

BLOCK

ì

'-l,-

r

a

t

6

I

t__ L_l

¡

a

I

__l

L-

3900

26

cÉ27

37A

AGC

oEf.

7

65C

Voltages

measured

termfnal to

chæsig

yith

a volt-ohm meter

-

no signd ild

l2 volta app¡ied to radio.

Total battery drãin

1.2 mps ât l2volts.

Tolerilce on voltage

lú.

Before meering tra¡rsiator voltagea,

a

l0

ohm spealer must

be comected

to

radio.

Vo¡tage

placed,

applied

shou¡d be meeaured

from

Irover

traDaiator

cæe

to

grannd.

If

pover

t¡a¡aiator ia re-

(¡tem

*66)

to

obtåin

prõer

cotlectör

voltege with

12

volts

adrust bias

Iþtentiometer

to redio.

I

Iten

#64

is

a fwe resiator

for

the

pover

tranalator. Seryice rit¡r enct

rep¡aceEent.

O

Pr¡ntea

oñ circuit bord.

ô

O

Wi¡t not

appeu in

aU radios.

CAUTIOI¡I:

Onfy

a l0 ohm speeler should be r¡sed on

t¡ia radio.

1.5^

E

ìf

rF

260

1C.

4

7

t4

B

æ27

AGC

OET

D

49

f-

I

LF

f-

Fisure 7l CIRCUIT DIAGRAM

-

985443

-

RADIO

k-"%-:þ.lE

SIGNAL

GENERAÎOR

o

ou¡rut æ¡trcr

fUNtNG

FÊEOUENCY

f¡EOUENCY

ac

10(E

t-".--"--iilÞ]

SIGNAL GENERATOR

o

ourpur @ntrcL

¡UNING

BC

&NO

m-J::þ':.?]

SIGNAL

GENERAÍOR

o

outpur

@Ntrcu

tuNrNc

FREqU€NCY

fONE

ÉREOUENCY

eNO

DS

505

OUTPUl

AMP

w[H osãì

os

22

LF

(gFvrcE

H

os 24

R,Ê ÂMP

(*RVTCE

W¡Ìx

6?5ì

I

J

É2f

A@

oEf

r-

627

ACC

oEl.

_l

0s

26

Â.¿ AMP

DS

25

T

I

FUSÉ

6LæX

5

t___

IIIus.

No.

Service

Part

No

850

mfd.,

16 volt

400 mfd.,

16 volt

4

mfd.,

11.5

R.M.S.

727875t

.022

mfd.,

75

v.,

tubular

7272519

.04?

mfd.,

75 v.,

tubular

72l25Lg

.047

mfd.,75v.,

tubular

7212519

.047

mfd.,

?5

v.,

tubular

7272519

.047

mfd.,

75 v.,

tubular

?281895

.0022

mfd.,

100 v.'

tubular

7282046

.1

mfd.,

75 v.,

tubular

Part of .000002

mfd.

circuit

board

?280995

.000091

mfd.,

100 v.,

!

\Vo

ceramic

Fisvre

72

S¡GNAL TRACING

PROCEDURE

-

985443 -

RADIO

Description

IIIus.

Service

No.

Part

No.

Description

.000120

mfd.,

!A0 v.,!

570,

ceramic

.000220

mfd.,

100 v.,t

570,

ceramic

.001

mfd.,

100 v.,

ceramic

.0022

mfd.,

100

v.,

ceramic

.0022

mfd.,

100

v.,

ceramic

.0047

mfd.,

100 v.,

ceramic

30

mfd.,

6

v.,

electrolYtic

100

mfd.,

3 v.,

electrolYtic

R.F.

Trim,

125-300

Mmfd.

Osc.

Trim.,

225-325

Mmfd.

Antenna

Trimmer

.47

mfd.,

100 v.,

tubular

3?A

378

37C

26

18

20

27

29

23

34

L7

28

7279896

25

7283835

30

31

32

24

19

33

2LA

218

16

38

7279773

?280630

7280630

7280?03

7279896

7279888

7281932

7281

93 3

7281971

?257906

b---

22

69

La pagina sta caricando ...

Chevrolet 985447 Radio Service And Shop Manual

Questo manuale è adatto anche per

Chevrolet 985447 Radio Service And Shop Manual

in altre lingue

Altri documenti