GE LBI31072 Phoenix Maintenance Manual

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PHOENIX*

MAIIIITENANGE

450470

MHz 20-WATT MOBILE

MANUAT LBI3 TTI72

COMBINATION

GEr{ERAL@ETECTRTC

LBr31072

TABLE OF CONTENTS

SYSTEM

COMBINATION

DESCRIPTION ...

SPECIFICATIONS .

NOMENCLATURE .

OPERATION

INITIAL ADJUSTMENT

Transmi

tter

Adjustment

Receiver Adjustment

Re-Installation

CIRCUIT

ANALYSIS

Transmitter.

Recei

ver

Channel Gua
Power

MAINTENANCE ...

Disassembly

Driver & PA

rd

Distribution

....

Transistor

Removing ICrs .

TEST AND TROUBLESHOOTING

Service

Techniques

Test Points .. ..

Transmitter Alignment

Receiver
Receiver Test
Receiver

Alignment

Procedures

Audio

and

Replacement ...

PROCEDURES

Procedures

Procedures

Squelch

lltaveform

Checks

1ii

15-16

iv

10
10

11
12

72

12
12

L7

l8

l9

1

2
2

2--

2

,

z

6_
7'

o

\/

,'

,\-

OUTLINE

DIAGRA.MS

Transmitter/Recei

I

n t

SYSTEM INTERCONNECTION
SCHEMATIC

ercon

DIAGRAMS

nec

t

/Osc

Interconnect/Osci

Transmitter/Receiver

SERVICE

PARTS LIST

PRODUCTION

Figure

gure

F

i

gure

Fi

gure

Fi

gure

Fi

gure

Fi

gure

Fi

Although
battery, high
possibly
burns.

SHEET

Hookswi

Externa

1

-

2

-

3

-

4

-

5 - Test

. .

tch
I Speaker

CHANGES

Transmitter/Receiver

Power Distribution ..

Lead Identification

Q251

Mechanical

Equipnent Set Up

6 - Transmitter
7

Receiver Troubleshooting

-

the highest

currents

.metal

heat

Be

careful

when working

ver Board

i

llator/Channel

DIAGRAM

11ator/Channel

Board

......

Guard Board

Guard Board

(Sheets

Block

Diagran

1, 2

ILLUSTRATIONS

Layout ....

Troubleshootlng

DC

voltage in this

may be dravrn under short

objects such as

tools, rings,

near energized circuits!

&,3)

mobile

equipment is

supplied

circuit conditions.

watchbands,

etc., enough

by

These

25-26

27

3L-34

the vehicle

currents

to cause

-29

can

24
24

23

30
30

32

11

L4

l6

2L

J

o

High-1eve1

upon

contact.

11

RF

energy

Keep

away

in the transmitter

frorn

these

circuits

Povrer

Amplifier

assembly can

when the transmitter is

cause

energizedl

@

Copyrignt

tgBl

cenerat

RF

Etectric

burns

Company

L8r31072

IDENTIFICATION

FCC

GF, IDENTIFICA?ION

FFEQUENCY

RANGE

Recei ver

Sque I

ched

Unsque lched

Transmi

FREQUENCY STABILITY

TEi{PERATURE
DUTY CYCLE
DTMENSTONS,

WEIGHT, LESS

POl{EB OUTPUT

CONDUCTED

HAR['ONIC EMISSIO}I

IiODLJLA T I ON

AUDIO SF.NSITIVITY

FREQUENCY

AUDIO

CHARACTER]STICS

DI STORT I ON

DFVIATION

MAXIMTIII

RF OUTPUT IMPEDANCE

S PREAD

FREQUENCY

tter

RANGE

LESS ACCESSORTES

ACCESSORIES

SPUFIOUS AND

SYi\4METRY

NUMBER

NUMBER

TRANSMI TTER

SYSTEM

(g

20

-70

r4,5
nodulation and

CG modulation

65 to
at

3.5 to 6 M'i I I ivolts at

Within
a 6 dB
emphasis fron
per
limiter filter

Less
Less than 5%

0.5

5.5

50 ohms

(+3.5

kllz

72O

Millivolts

J91 1-4

+1

dB

per

EIA

standards.

3%

thA!

kHz naximum

MHz

X W

kHz volce

0.75

)

to

octave

300

per

(1000
(300

X D)

dB of

-3
pre-

to

FCC and

Hz)

to 3000 Hz)

SPECIFICATIONSI

kHz

3OO0 Hz

Post

AXAgMZTRlO 1A
TR1O1A

450-470

I'IHz

250 milliamperes
650 milliamperes

5.5

Amperes

0.0005%

-30"C

2O% Transmit,

(*22"F)

65 MM X 190

(2.55

2.O7

AUDIO

ohms

SI]NSITlVITY

12
20

SELECTI V I TY

EIA Two-Signal

SPURIOUS RESPONSE

INTERMODULAT I

MODULATION
SQUELCH SENSITIVITY

FREQUENCY

RF

]NPUT IMPEDANCE

OUTPUT

speaker)

dB SINAI)
dB

Quieting

Method

Me t hod

X

7.5 X 9.4
(4.5 pounds)

kg

(to

4.0

ON

ACCEPTANCE

RESPONSE

13.8 Volts

@

+60oC

to

100%

Receive

MM X 240 MM

inches)

0.4

o .45

-85 dB @ kHz

dB

-85

dB

-75
+7,O

kEz

<8

dB SINAD

Within

staodard 6
de-emphasis
300 to 3000
reference

50

ohms

(140"F)

+2

and

dB

curve from
Hz

)

-8
per

(1000

dB of

octave

a

Hz

*

These

specifications

appropriate

intended

are

Specifications Sheet

pri.marily

for

the complete

for

use of

the

specifications.

serviceman.

Refer

to

the

LI_) 1:i

10 7 2

DESCRIPTION

Phoeni

ri

Genera I

na.tions

L.,oth di

circujts
rarJio

i s a sel

recejver
er.
fr:ont

The

the

Its

mounting

stanclarrl

following:

o

o

Ill ect

ful1y

are

screte

(IC's)

built-in

with

I 1 size

sma

combinations

One receive

transmi

P1 ug-

oscil

j

lator
o Channel
ll'he raclio

t-di ssipating, aluminum

hea

frame

mountecl.

mounted

includes
The

(

IOC) board contai

oscillator

cessor

ne1

on which

The

transmitter/receiver

on the

FF

and

Interconnect/Oscillator/Channel

circuits,

mi crophone

,

Guard

rcuitry.

ci

tors, controls

irectl)'on

c]

anC ease of di

the

sassemblY.

c

transistored

components

high

for

f-contained,

controls

makes

in

conventional

frequencY,

t frcquencies

n crYsta

litY

stabi

Gr-tard

(tone

consists

ci

two

bottom

of

receiver

1 I interconnections,

ns a

transmitter

preampl ifier

Al 1 externa.l

indicators

and

two boards

x mobi

anci

Ie

utilizi-ng

--
integrated

reliab'i1ity.

transmitter/

FM

and

it idea-I

vehicles.

are equipped

I

for

s

squelch)

effective

an

of

die

"H"

audio

boards

frame

circuitry'

rcuit

the

audio

and

,

are

rellability

for

combi-

speak-

and

+0

0005%

'

cast

board

Guard

Chan-

connec-

mounted

The

for

with

two

rrHrr

are

is

and

pro-

cover
receiver

plugged

provicles

board.

An

optional
onto

alignment

ments can

or a

TRANSil{ I

citer
band,

power

rated
sensing

temperature and/or

as
specified

be

mul-timeter,

TTER

The

transmltter

with an

fixed-tuned

output

power. Once

control circuit

limits.

access

set

the test

troubleshootlng.

and

made using

audio

power

level

is

Frequency stability

transmitter

an electronic

IVER

RECE

The

a front

of

and receiver

compensati-on

dual conversion

end section
sections operating at
The receiver also
audio
a

section.

3-watt

audio

contains a squelch and

The audio section

output into a

tLe transnri

to

of test

pins

GE

consists

processor

probes

on the

Test Set 4EX3A11

of an

and a broad-

amplifier.

pre-set

the

lnternally to

1eve1 1s set,

holds it

voltage

for both the

is maintained by

network.

receiver consists
and two mixer/IF

21.4

NlHz and

4-ohrn

board for

Illea.sure-

constant

vary

455
provides

load.

ltcr/

be

can

FM

ex-

The RF

within

kHz.

a

\*

plug

The hoarcls

i na ting

The

the need

only

wires

plug-jn leacls

The

top anr!
frame ancl
the radio.

jnside

the

The

highly durable

bottom

provide

The internal

the top cover"

of

front control

plastic

and recessed controls

requirements.
four standard
crn/Off

pushbutton,

The

operator controls:

pushbutton (fixecl

monitor), a

contr()1

ector

I

cator

green power

t.FD

No

highest

providr.d

i s de.si

negative

rotary, an

and a two-posi

,

(RpTR-DIR)

(Light

indicator

on

pou'er

supply

supply

voltage used

by the

gned

for operation

ground

The'radio is

into

for i nterconnecting

used in

the

for

covcrs

optimum

for

panel

a

squelch

. A

tting Diode) and

Fmj

is
vehicle battery.
vehjcle systems.

modular

of

Both major modules and

easi 1y accessiblt'.

are

screws i n thc'

vides access to

rea r of

the inte'rconnect

frequency/interconnect

in

the two screws

the

each other,

wires.

the ra.dio

internal

enclose

are

speaker.

the

protection for

speaker

panel

rounded

wlth

passenger

provides

mounts

made of

is

access

corners

safety

a

momentary

and

edge-mounted

tion

frequency se-

MONITOR

Channel

Volume

red Transmit

provided'

are

required since

in the

only

radio

The radio

12 Vo1t,

in

construction.

tuning adjustments

Loosening the

the top cover

multi-

or

board.

rear of the

Loosen

bottom

elim-

the

rrHrr

on

to

POWER

Guard

indi-

the

js

two

pro-

i ng

AC POV/ER SUPPLY

To

use

optional

is

available.

the

length

cated

On LED

power

M ICROPFIONE

121 Volt AC, 60

power

permits

away

located on

is

supply.

The

standard

an electret

housed in a sturdy case, and the extendable

coiled cord
of the radio. The microphone is secured

a

radio by means of a strain relief hook

the
on the microphone cabIe.

hanger is supplied with the rnicrophone.

HOOKSWITCII

1n

microphone hookswitch may be suppli.ed

the

a Channel

Channel Guard

radio. The

Guard

Placing
position (towards
dlsables the

the switch

OPTION

radio

the

An

supp)-y

from

eight

to the

the

the

power

mobile

microphone,

plugs

OPTION

into

hookswitch

disable switch,

the switch

the smaIl speaker syrrbol)

receive

in

the

base

as a

llerLz

foot

station, an

power

cable connects

radio. The cable

supply

radio. A

front

the

green

panel

combinations use

The

mi-crophone is

jack

a

at

A

appllcations, a

is

equipped

in

Channel

"down"

Guard. Iti-th

position,

supply

to be

1o-

Power

of the

back

the

microphone

wi-th

with

the

"up"

the

to

LnT31072

DESCRIPT ION

Channe.l CrrarC

microphone

EXTERNAL SPEAKER

A

LFXANo

3

watts.

3.2

ohms.

pin-s

to

Externa

the

H13

from

removed

hui I

t-in speaker. A LEXANo

j

p)

ed for moun t i ng.

Complete

Two-lVay

the
rate Operatorts

dures for

ges

messa

TC

RECEIVE

1.

2.

js

removed from

five-inch

housing,

The

The

3

and

7

I Speaker

H14

to

P904

or

Radio

receiving

fo 1 1

ows :

A }.4ESSAGE

Turn

POWER

the

Push

in

able

the

nel Gua

volume

I istening

provides

nomina

speaker leads

of Systems

on the

unplugged

OPERATION

operating

Manual.

the

the I,{ONITOR

rd

control

the I\{ONITOR

operation.

The

messages

radjo

from

is

other

is disabled when the

the hookswitch.

(OpTTONAL)

speaker,

contained in

an audio output of

I speaker impedance

are connected

plug

are

is used,

(IOC)

board

to disconnect

bracket is

instructions

provided

The

basic

P910.

the

in

IVhen

jumper

can be

the

sup-

for

a sepa-

proce-

and transmitting

radio

pushbutton.

squelch

on by

circuit

decoder. Adjust

for

level

and then

but

ton f or

now ready

radios

in

pushing

button

to dis-

and Chan-

the

a comfortable

release

norma 1

to receive

the system.

in

is

electronics

Second

(where

a

TRANSTI

I

Adjustments

clude measuring

power

optimum

and adjusting

to rated

frequency

mea

suremen

records.
justment,

(see

Table

RECEIVER

The

ver

includes

match

justment

Procedure

CHANNEL

the antenna.

All
Guard.
is not
circuit
to J910-9.

present.

RE-

INSTALLATION

If

moved

the

to

battery potarity

technician

Class FCC

requi red

TTER ADJUSTIVIENT

Radiotelephone

.

)

for

the

VSIJR,

power

then setting

output. Next,

and

modulation

s

t

on the FCC

For

the complete

refer

to the

of Contents).

ADJUSTMENT

initial

adjustment

tuning

Procedure,

(see

Table

GUARD

1n

desired,

DISABLE

radios

are

applications

disable

by connecting

Also,

remove

the mobile

a different

who holds

the Lransmi

forward

the

and reflected

antenna

the transmitter

measuring

and entering

requi

transmitter

Alignment

for
the input
For

refer

the Receiver

to the Alignment

of Contents).

equipped

where

jumper

a

with

Channel

the Channel

the versatone

combinati.on
vehicle,

of

the new

always

Firsl

a

license

tter in-

length

red

these

sta t ion

Procedure

the recei-

circuit

Channel

Guard

from

Guard

J910-B

is

system.

check

or.

for

the

ad-

to

Ad-

if

ever

TO

TFANSI4IT

'|

2.

After
described
following

2

A I\,IESSAGE

Turn

the
the
tion.

Press

phone

radio

Receive

"To

PTT

the

and

speak across

the nnicrophone
level.
soon
given.
the
tirne
pressed,
transmitter
receiver

mitter

the radio

in

adjustments

Release

a s

he

t

The

red

control panel

the microphone

inr!icating

is

is rnuted

is

keyed.

INITIAL

ADJUSTMENT

has

the Installation

should

on

as clirected

a lr,lessage"

switch

jn

a normal

PTT

the

ge

messa

inriicator

will

PTT

on

the

when

been

be

on

the micro-

the face of

switch as

ha

s been

I

ight on

glovr

switch

that

air. The

the

trans-

installed

I\4anual),

made

by an

in

sec-

voice

eacb

is

the

(as

the

CIRCUIT

The

control
two-frequency
frequency

ter

components

transmitter

U1O1;

Q153,

ampl

control

led,

uses

osci I

exciter

i fier

circuit

transmitters

frequency

operation

band.

integrated

for

increased

consists

1a

tor

stages

Q251

exciter provides

wa t

ts

of

provides
block

transmitter

I\{ICROPHONE

A

associated

modula

rated

diagram

of the

and

PREATIPLIFIER

preamplifier

circuitry)

output

ANALYSIS

TRANS}{I

TTER

utilize

modulated

in

The

solid

circuits

reliability.

of audio

Q151,

through

q2S4

and

e201

Q253,

through

through

approximately

ted

RF

to

power.

radio

receiver.

stage

provided

is

a

exciter

4bO-4TO

the

state

and

processor

Q15t,

and

e287.

150

the

Figure

showing

(e901

crystal

for

transmit-

trtiHz

discrete

The

buffer

e2O4;

power

The

milli-

pA

which

1

is

both

the

and

for

the

pA

a

FF-

45o-47o

MHz

2t.4

uxz

[c,

RCONNECT/OSC

/CG

--l

R ECE

TR

AIiST

I

xrAL

rx

xrAL FRE.

Rx

AUDIO

FREa.

=

-J

E#!I:

=

F3

MUTE GATE

k-

so.o-*z.zzz MHz

-

l5O,O

1 56.566

-

MHz

455 KHr

.--l

LB13

1072

e!!4

osctttaloRz

MIXER/IF

u 50r

AMPL

VOL /SOUELCH HI

FROM CHANNEL

GUARD

A

UDIO

MUTE

GATE

o 605

cERAt'llc

FILTER

(455KHd

2502

AUDIO

AMPL

u6

IF LIM /FM DET/

AUDIO

PRE AMPL

u30?

R 521

AUDIO

LEVEL

0l

;EIVER

TTER

SMI

Z

HELICAT

RESO

-

NATORS

t2t4,L2t5

POWER

0254-

CONTROT

A257

45O -

47O MHz

sxclrEn

e-L+

PwR. AMPL.

RC4240

Figurel-BlockDiagram

L8I31072

CIRCUIT

ANALYSIS

standard
built-in
circuit is

coupled

electret

preamplifier.

located

With

this microphone,

througb J911-5
stage. The
through

cessor.

bui

through

AUDIO

pre-emphasis

post

approximateTy

audio

U101B

audio

through
sisting
+4.25V

R908

For

I t-in

J977-4,

PROCESSOR

The

audio

limiter

processor.

and,

The

processor

p9O3-2

of R101,

output

optiona

preampl

4

8.5 Vol

establishes
for

both

provides
of

both

operational

an

operational

Resistors

D101

Diodes

+7.7

R110
cathode

of D102.

D101

permit

and

D102 provide

and

D101

VDC.
and R111

D101

of

The

D102

and

DC

a

the

voltage

biasing.

When

a

magnitude

U1018-7

at
amplifier

Itfhen
exceeds 4

conduct
cycles
reduce
limits
volts

the

such

does

provides

the

audio

volts PP,

on the

providing

the

the audio

PP.

Resistors
comprise
that

R107

curve
trol
pre-emphasis.

attenuated,

the

enhances

and C1O7

below

limiting.

the cut-off

the

Audio

microphone

is

on

ampl i

fied

and C905

1 microphones

i fier,

bypassing

U1O1

n"o".=.o.

with

amplitude

filtering.

24

dB

dB

by

U101A.

t regula

and

applies

to a voltage

R111,

from

the

operating

ground

AC

amplifiers.

R109,

D102

and

Voltage

provides

and

voltage

is 4.25

level

change

divider

input

signal

that

not

exceed 4

a nominal 20

signa

positive

100%

amplifier

amplitude

R105,

audio

the

signal

control

point

As

high

gain

from

the

coupled

microphone

the

board.

preamplifier

The

IOC

MIC

to the

preamplifier

output

to

the audio

audio

MIC PRE

provides

limiting

A
is realized
20

dB

total

is

tor

through

provided

powers

regulated

divider

R110

and R109.

the voltage

reference

amplifiers.

at the

R110,

summing input

R111

limiting

are reverse

divider
+2.6

at

VDC.

network

+b.9

VDC

VDC

at the anode

junction

the

C104

between

network

U101B-6

to

the

amplifier

volts

1

level

at

diodes D101

and

negative

gain

negative

feedback

to

at U1018-Z

R106

and

R10?

pre-emphasis

to noise

pre-emphasis

the

R106

and CLOT

for

high

frequencies

U101

of

is increased.

preamplifier

to

the input

wi.thout

HI

is

coupled

pro-

with

is

coupled

AMp

e901.

audio

and

gain

the

the

+8.5V

con-

The

divider

point

C1O6

and

diodes

for U101B.

biased

R109,

at

the

and C108

U101B-z

for

diode

is of

output

p-p,

the

gain.

dB

U101B-7

and D102

half

1.

This

to b

and ClOz

network

ratio.

con-

frequency

are

or

of

at

of

to

is

of

by

a

a

operational

amplified

through

second

R114,

operational

The

applied

combined

U101A,

per

dB

vide
for

to

with

post

A

R112-R114,

octave

an

additional

a

total

R112-R114

tolerance

a ssure

post

replacements.

The

Q152.

A

output

OSCILLATOR

tempera

is

coupled

compensated
and

TRANSMIT

consi,sting

and

C151

over

a temperature

The

temperature

audio

through

is

MOD

Modulator

frequency
the

audio

Q151,

comprise

rates

RF

osci I

a

the

carrier

lator

operating

lator

is

output

then

coupled

circuitry

boa rd .

The

identical

desired

frequency
frequency
switch

emitter

grounded

selected

Q154.

Q154

is

of

through

oscillator

amplifier

output

Channel

U101A-2.

the

limiter

roll-off.

of

SERVlCE

are 7%

proper

limiter

through

of U1018

R7I2

,

amplifier

Guard

microphone

C10B

6

18

must

dB

dB.

be maintained

opera

filter.

of

the

C110

R104

(CG)

The

filter

and C110

R104

per

resistors.

post

to

transmitter

ture

of

R151,

maintains

applied

ADJ

varactor

at

the

processor.

Y1b1

Colpitts

ninth

compensa

R152,

oscillator

range

compensating

of

to FM

control

D151

varies

audio

and

rate

associated

oscillator

subharmonic

frequency.

is

adjusted

frequency

is

applied

through

L151.

by

to buffer

p1b1

transmitter/receiver

second

to

swi

tch

normally

the

oscillator

the F1

is

S1b1

turned

selected

S151

and

on.

oscillator.

selected

and

Q1b4,

U101B-6.

is

and R11Z

U101A.

tone

CG

tone

audio.

consisting

provides

and C102

octave

This

tion

of

Use

exact

limiter

the

temperature

oscillators

ting

R1b3,

R154,

frequency

-30o to

DC

voltage

modulator

R155

and R1b9.

the

applied

circuitry

which

(50

MHz)

The

the

transmit

assigned

to

The

e153,

to

the

stage

through

channel

on

so

oscillator

tqrning

The

coupled

to

input

is

then

pro-

roll-off

to

the

filter

Q151

network

D1b1

+60.C.

and

DIS2

transmit

from

g.ne:

oi

the

oscil-

and

exciter

(Tx/Rx)

is

The

Tx

Common

that

the

is

the

a

is

of

12

CIRCUIT

ANALYSIS

L8r31072

SERV I CE

Tbe

channel

factory
circui
to

posi

t

be checked

tion
consists
Groundirg

J911-6

each

turnecl

transmit

and then

EXCITER

The exciter

the

a

450

output

amplifier

two

and

takes
buffer circuits
multiplies

and

milliwatts

power

these
of
width
sive

buffer

the
a

amplifier

functions,

filters

the

and spurious

harmonics)

of
The

output

stages

exciter

tap on

L2O1.

voltage to
L201

harmonic

J151.

provides

along

C2O6

pole

two

C2l4 match

and

sistor

(150

and

filter to the

approximately

to the

filter, consisting

emitter

voltage on

monitored at

vcl

ts.

C216 and

the base

to
Q202.

at'lP2O2,
tripler

The

and

has

A matching

C222 matches the

and

tripler
ter,
filter

a two

to the

L2O7

is

tben

stage, broadbanded

consisting

L210

and

L211

the collector
providing

the necessary

common

test

PurPoses

permits

regardless

S151.

of

of

Q154,

channel

turns

off

oscillator

grounding

by

on

P911-8(F2

consists

(150

\llIz

amplifiers.

I{Hz

from

(2

milliwatts

amplifies

minimum

(45O-47O

circuitry.

the

whicb

characteristics

of

of the

is coupled

J151, which

via

This tap also

the buffer

with

L2O2,

\!lHz) rvhich

C2O7 natch

the collector

input of

of

Tp201,

C2I7 match

the

of

voltage on

base

is t1'pically -1.2

approximately

network

first
L2O8.

and

matched

of

of

and

Q203

provide

Q203

Although this amplifier

viding
hiased

ensure

exciter

12-I5

to

no

output.

dB, and typical

dB of

provide

AM

components

power

adequate

Typical actual

circuit

is

onlY.

frequencies

both

of

The

circuit

C168.

and

Rt72

Q154

common

and

P911-7(F1)

lead

Permits

to

).

a

of

45O MHz)

to

The

the

1t to

minimum)

provide

I 1a tor

osci

I{Hz)

In

addition

exciter

determine

the

contains

the

transmitter'

1a tor

I

osci

to the

is connected

transistor

selects

the

base

10

dB

present

is

output

of

Q201'

gain.

of

of

the

this

another

L2O4 and

LzOl

is typically

and

(AMPL-1)

L205.

the output

Q2O2

dB of

transistor'

ean

vo1ts.

tripler

3

consisting

450 MHz output

two-po1e

The

by

Q204

proper
to the

helical

output

C223 and

450

[4Hz amplifier

. C227

matching

base

bandwidth

is capable

gain,

both

stages

saturation

present

are

gain

150 mW.

output

is

for

The

the

be

1.50 llHz

tripler
exciter

to

band-

(exclu-

input

supplies

Q153.

third

thls

of

which

C273

tran-

pole

two

can

+0.3

L205

of

read

be

gain.

L206

of

of the

fi1-

of this

L209

C228

,

from

of

Q2O4,

as we11.

pro-

of

at

is

and

and
140

the

to

aIl

and

of
to

aL

The

be

The

are

the

7-9

to

to

The collector

input of the

the
filter
and
sisting
relative
this
volts
after

(L214

L213.

An RF

of C236,

power

filter

to be

is typically

tuning

and

the exciter.

There is no test

rela tive

TP251 in the

power

final

done while

test

detector

power

coming

tuning

monitoring

points

There are

which

W201,

require

probes.

are approximatelY

W2O4, W205 and

interface
to the

These
used

other exciter

points

monitor or

to

PA

out

for

SERVICE

4

the

for troubleshooting

50

using

ohm

nations.

POWER AMPLIFIER

The

three

sists of

power

cuitry.

is applied
transistor

The

colleetor

the output

of

variations at any

driver

of

Power Amplifier

Amplifier

ifier

ampl

Collector

q252

from

q257

voltage for

matching network consisting

,

C268

C267

Collector

A+

frorn

through

The 20

nected to

to antenna

then

POWER ADJUST

RF

The

'

the
power.

control

driver
The

output

transmitter to be

The

ling the

Q252

pass

C269.

and

voltage for

watt

1ow-pass filter by

the

power

through

tra nsistor

feedback loop consisting

power

Q256.

R260.

The

of

Q204

second

L215)

two

C233-C235,

by

"sniffing"

C237,

available

D2OI,

monitored

at

at

present

point

of this

coming

sect.ion

out

indicates

of

Q251

L214 and

L215

this test

use

the

points

2

in the

W251

helica

circuitrY).

can conveniently

inject signals

and testing

sources

stage

Q251,

Q253

voltage

and

power

driver

associated cir-

and

for driver

A+ through

L256,

and

power

given

is coupled

Q253

L267,

through

L262

L257

Q252

setLing and

time.

to the base of

Q253

and

output of the

relay

CIRCUIT

power

K601.

adjust circuit al1ows

set to rated output

adjustment

DC

lector voltage to

col

pass

transistor

i s control

of

is set by

is matched

pole

helical

circuiL

and

R221 allow

input

the

TP203.

point

thj"s

at

indicates

that

fil ter

relative

(Amp1 4)

,

should

point. No

of special

exciter

50

ohrns.

(which

I fi1 ters

be

termi-

amplifier

power

and

q252

control

R256.

is a result

voltage

The

output

an impedance

provided

PA

is con-

W256 and

I

ed by a

through

C292,

q257.

of W254,

is

R258.

is

attained by

Q254

potenLiometer

to

L272

con-

of

+0'6

and

be

RF

con-

and

Q252

L8r31072

CIRCUIT

ANALYSIS

A

D252
change

output

goes

change

causing

accordingly.

power

more

conduction which

age.

Q254

increases

duction.

to the ba se of

Cecreases

Q256

voltage

base

resulting
lowers

q252,

proport

the col

tberetry

ion to

a1ly sensed by

The

superheterodyne

in output

the

base

increases, the

positlve,

causing

lowers

controls

Q255,

conduction,
This

raises the

Q256.

proportionally,

pass

of

transistor

decrease in conduction

lector voltage of

lowering the output

the excessive

the base circuit

RECE I

receivers are dual

FI\'I

receivers designed

one-frequency operation

frequency

used

audio

supply.

'The

quencies

for

PA

all

range. A

receiver stages except

IC,

whjch operates from the

regulated

receiver has intermediate fre-

21.4

of

liHz

and

power

voltage of

For example,

its col

Q255

Tbe

VER

in

455

is

sensed

q254

if the

base of

it to

increase

lector volt-

therefore

as

decreases

voltage applied

conduction

lowering

Q257.

of

driver

power

power

of

ori

Q254.

conversion,

42O-572 \lHz

Ihe

8.5 volts
for the

kHz. Adjacent

by

to

Q254

Q254

con-

of

the

The

Q257

in

gin-

for

is

A+

channel selectivity is obtained by using
two band-pass

fi I

ter and a

Al1

the

transmit

osci

receiver

455

of the receiver

1 1a

ter/receiver

consists of:

filters:

kHz

tor

is

21.4 MHz

a

ceramic

fi 1 ter.

circuitry

mounted on the

(Tx/Rx)

board.

crystal

except

The

frequency
crystal operateci at one ninth
required injeetion frequency.
variable

connected

capability.

is control led by

capacitor

in

series to

The

D301, L301

provide

compensation

third mode

a

of

Voltage-

Y301

and

compensati-on

voltage used

the

are

to control the transmitter oscillators is
applied to
L301

is
frequency. R301
to insure

of the

C304 to the

output

crystal.

The

of

two tuned

Tx/Rx

board.

the third barmonic

quency

Q351.

coupled
through helical resonators L354

L354

and

frequency

nultiple

The

multiplier

The

meter reading

ly 0.8 VDC. The

oscillator/multiplier

to

the mixer

meter

1
tor

1ST

reading

volts

Probe.

I{IXER

D301

maintain

to

stability.

adjustable to set the oscillator

is in

parallel

with

operation on the third overtone

output of

emitter of buffer

is coupled through

Q302

circuits

L351

Q301

(L351

and

is

coupled through

Q302.

L352)

and

L352

are tuned to

P301

on the

of the oscillator fre-

which is

The

to the source input

applied to the base

output of tripler

of

A351

mixer

and

L355

are

tuned to the operating

minus

of the

DC

27.4

MHz

which

is

crystal frequency.

leve1

of the

osci

chain can be monitored

at

RF

point

this

frequency

is

the ninth

1 Iator

TP351.

at

typical-

from

chain and input

can be measured

at

measured

as

TP401

is

using the Rx RF Detec-

TP401.

at

typically

0.5

Y301

The

Q402

L355.

the

level

The

to

of
is

/

to

Receiver

21

.4 MiHz

1st

and

455

kHz

Detector

Audio

Squel

RECE]VER FFONT ENI)

An RF

conpled

helical
t'ase of

Q401

through

resonators

RF

is

coupled

resonators
gate

of

1st

lectivity is

resona tors.

OSCILLATOR

Q301

make

up

PA

ch Ci rcui t ry

signa 1 from

amplifier

consisting

Mixer

provided

IVIULTIPLIER

&

Y301

,

Colpitts-oscillator.

a

Front End
1st

IF

2nd

Oscillators

2nd

IF

Circuitry

antenna

(L401

Q401.

through

Q402.

nd

a

a ssocia

circuitry

circuitry

the antenna is

and

K601

L4A2)

relay

The

three

of

by

more

L4O5-L4O7

The

front

the

five helical

ted ci

FM

with

and

to the

output of

helical

to the

end

rcui

The

two

se-

try

The 1st

active
high

device. The FET

input

an output

products).

tion

In
end
of the

the

helical

mixer. Injection
multiplier
of

the

output

Q402

(L409

2501.

provides
IF
is

work

IST

I{OSFET.

plied

mixer. The 21.4

signal

through

and

The

highly-selective

the

selectivity.

coupled

L501

2ND

&

1st

IF Amplifier

The

Gate 1

to

ampli-fied

The

biasing

determines

mixer

impedance,

relatively

mixer

filter

stages is

is

coupled frorn

an impedance

C410-C413

first

The

through

to
IF

1st

the

DETECTOR

&

crystal

of the

signal is

Gate

on

gain

the

uses

a

high

(Q402)

FET

mixer

provides

power gain

free of intermodula-

stage, RF

is

applied

from

to the

the front

voltage

applied to

MHz

the source

mixer

the

matching

to crysta 1

)

crystal

portion

output

impedance-matching

IF

of

amplifier.

STAGES

e501

filter

the receiver

of tLre

is

dual-gate

output

amplifier,

taken from

2

and the

of the

the

drain

stage. The

as the

and

gate

from

the

1st

lF

drain of

network

filter
filter

filter

net-

is

ap-

and

the

drain.

load

a

o

CIRCUIT ANALYSIS

L8r31072

amplifier

gain.

IF

provides

through an

(L502)

the

of the

that

input of

U501

and associated

2nd

amplifier.

Y501,

is

20

"945

2nd IF

side
for those

and the oscillator

lllHz

(standard),

injection with

radios

The

impedance

matches

IC U501.

oscillator,

The

f or lovr side

approximately

output

the amplifier

crystal

or

(Structured Option

determined to

on a tweet frequency.

mixed

with

21.4 MHz input.

the

of the mixer is lirni.ted

L503 is

quency.

ceramic

kHz

tuned

The

output

filter

selectivity, and applied

for the

of

Z5O2

455

U501 is

wlnich

Point TP501 is used in a

ver,

and can be

u501.

U502

and associated

455

of a
detector

is the

Level

kHz
and an audio

quadrature

potentiometer

audio output level

used

to

limiter, a

detector coil.

R521 is used to set the

to the audio

of

Q501

matching

circuitry

mixer

20

is coupled

output

consists

and

of

dP

network

to

2nd IF

for the oscillator

in

ject

operates

ion of the

aI

21.855 MHz for high

be operating

FT)

This

by

D501

kHz

frequency

The output

2nd lF

coupled

provi.des

U502. Test

to

ligning the

check the

and

output of

D502.

fre-

through

455

the

recei-

is

circuitry consists

quadrature

preampl

i fier.

type

L504

Audio

FM

amplifier.

1oad.

The

output

is

noise

7 k{z.

The

noi

Squelch

which

Q602

se output i s coupled through

control

R607 to expander ampllfier

improves

the level discrirnina-
tion characteristics of the
output of

voltage
This

and operates as

circui t has a high

Fol

Q602

doubler

lowing

Schmidt trigger

trigger

and a

IIUTE

provides

1-defined

we1

gate

Q605

Wi

th no RF
detected noise
output
This
volts
This

turns on

causes

pin

to

voltage

is

applied to a

circuit

average value

an

vol

the

(Q603-Q604

tage doubler

the necessa ry

output signa I for Rx

signa 1

Q605

2

a t the

Q603,

to turn on,

of audio

turning

turns off U601

(D603

source impedance

vol

receiver.

When

noise
drive

Q603

turned
This

at the output
to

and al1ows

oD,

turns on U601

an

e603

Rx

RF

signa I is

is

removed.

Q604

IVIUTE

of

Q601

to turn on.

gate

so

that audio i-s

at the speaker.

in

a band around

circuit.

and

rectifier.

. The

)

hysteresis

present,

tage

off

applying

amplifier

and mutes

received

decreases

This

turns

With

Q605

turns

The

passive

D604).

is a

Schmidt

the

doubler

Q604.

+1.

U601.

the

the

,

and

off

Q604

of f

heard

.

AUDIO

Audio

tone reject filter through

to the de-emphasis
The
network

Cont

speaker at

three

R637,

fiers
vide the higb

above

DC

(Q605)

These
squelch

the

through

Squel

noise components
detector

AND

SQUELCH CIRCUITS

Audio

is

applieC

to the

Channel Guard

P903-3

network through

audio

passes

(R633,

rol R634.

Audio

arnplifier
the

watts).

R638

and

closed loop
6

kHz.

The

audio amplifier can be

voltage

from the

through the de-emphasis

C608

C609

and

IC

)

U601 drives the

desired audio level

The

C611

plain.

audio

feedback

determines

loop containing

R636

and

frequency

receiver

the ampli-

muted

mute

which uses different logic inputs.

inputs are

signal.

Channel Guard

P903-4.

ch

Tbe

squelch

output.

8.5 V Tx,

The Rx

MONITOR, or

MUTE function from

circuit which

circui t operates

contained

The

output of

in the

is applied

applied to frequency selective
arnplifier

(L601,

Q601

R604

that has a

and C6O2) as the col

resonant circuit

and back

P9O3-7.

Volume

to

(up

pro-

C613

rol 1-off

by a

gate

on the

U502

noise

lector

to

FM

is

The

R607 in

fier

Q602.

Pressing

the front

disable

the base

squelch

the base

of the

the Channel Guard. It

of

sensitivity is
circuj.t of

in

the

radio opens

and

Q601

expander

MONITOB

disables

adjusted

ampli-

pushbutton

the Rx

also

the

MUTE

grounds

squelch

by

on

to

function.

CHANNEL GUARD

Channel

encoder/decoder

quencies
The

encoder

to

the transmitter. The

in

conjunction

all

calls that

proper

Channel Guard

The

of discrete

a

disable, PTT
switch; four

modules

Encode

consisting

Module

Selective

Versatone

U1004

in

For

nel Gua

rd

troubleshooting

References

in

the fol lowi-ng

Gua

rd

is

for

in

the

provides

operation

71.9 Hz

tone-coded

with the receiver

are not

frequency.

Channel

Guard

components for

switch,

thick-film

U1002,

Frequency

Decode

of

Amplifier (FSSA)

Network

ZIOOI

the tone reject

f uncti-ona

a

Encoder/Decoder

I di.agram

procedures.

to

symbol numbers

text are found

a continuous

on

210.7

to

decoder

tone fre-

Hz

modulation

operates

to inhlbit

tone

coded

circui try

wlth the

consists

the

and receiver

integrated

Module

U1003, plug-in

Swi.tchable

and monolytic

filter.

of

the

refer

,

mentioned

tone

range.

Encode

mute

circuit

U1001,

Chan-

to

the

on the

IC

Ltsr31072

CIRCUIT ANALYSIS

Schema tic

Diagram,

Outline

Diagram

and

Parts List.

FSSA

Frequency

(FSSA)

fier

bandpass filter for

Switchable Selective

U1003

frequency range.

is a highly stable

71.9 Hz

the

The selectivity of

2I4.7 Hz

to

Ampli-

active

the

filter is shifted across the bandpass
frequency

Networks

The

the tone

determjned by the

FSSA

the

precision

is

a

ENCODE

V/hen PTT

Gua

ne I

range

in

the

gain

by swi tching

fi I ter

of the

frequercy.

Tone

circuit.

Versatone Network

resistor network.

t

swi

rd

encode t one i s

ch i.

coupling the output of

U1003

inverting amplifier
circuit.
from U1003
inverting

back to its input

circuit and a limiter

The

output of the

to

the

amplifier at

rcui t

ci

FSSA

is a

The Tone Frequency

Network

s

opera t ed

FSSA

bandpass filter

through a

input

FSSA is

U1002-9.

Versatone

.

function of

connected

the

,

genera

of the

21001

Cha n*

by

ted

phase

coupled

phase

is
in

the output

peak

to
the
it to

coupled

peak.

to

The

Pin 12

proper

pass.

to

output from the limiter is

of

to an amplifier
amplifier
put

of a threshold detector

In

at

the
er in U1001
quency,

mutes

mode,

MUTE lead

Q1005

the

Q1006

and muting

Audio

tone reject
is an

active

associated

7O

while
back

tered

210.7

to

passing

to the recei'rer

VOL/SQ

STANDARD TONE

U1001-13

at

FSSA U1003.

frequency,

The

U1001-3.

circuit.

U1001-4

mute mode,

detects the

turns

receiver

is

operating,

from VOL/SQ

filter.

filter

circuitry.

Hz

are rejected

all other

HI

).

55

the

Lo

Since

FSSA

millivolts

the tone is

will a1low

output of the

U1001-3

is

coupled to the in-

when

Channel

Q1006

audio.

is

The

output

U1001-6.

at

the tone decod-

Guard

off.

In

the squelch

grounding

receiver

the

HI

is

The

consisting

A11 frequencies

applied to the

tone reject

of

by the fj.Iter,

audio frequencies

audio

FREQUENCIES

circuits

(Hz)

coupled

FSSA

is

the input

of the

fre-

This

un-

the Rx

audio.

filter

U1004

and

from

(fil-

An

amplifier
of the tone frequency
output
circuit
input

put
the
to

of the

is

of the limiter

A

limiting network

coupled from U7402-4

The

limiter

(U1003-12)

FSSA

peak.

provides

at the output.

phase

inverting

coupled from

circuit at

at

circuit

encode switch. Keying

+5.4

applies
the

ci rcui t osci I 1a

cy is

determined

nected in

The

is taken
tone

output

adjustment

Volts

to

t i ng. Tbe

by the

FSSA

the

circuit.

tone output

U1002-7

from

ampl

81010

i

fier
to

UlO02-2.

of

the encoder

and

Q1002

the audio

the transmi tter/receiver

DECODE

Aud

i

contains

pin

to

U1001

stage,
ter
The

U1001-15

is

the input

o from

the

1

of

is

the input

pass

low

attenuates frequencies

output

is

Vol

ume/Squel

correct

Decode

Module

filter. The

of

the 1ow

applied

to

of a limiter

frequency

of an

U1001-14.

phase

180o

amplifier

U1002-6

to the

U1002-5.

sets the tone

to

53

the input of

millivolts

is

also

used

the transmitter

This

starts

tone frequen-

tone

network

circuit

coupled

and

through

modula

processor

board.

ch high

is

coupled

U1001. Pin

act ive,

pass

low

21O.7

over

pass

fi lter

U1001-14

circui t, limiting

shift

The

out-

peak

as an

con-

t ion

on

tha t

1

of

three

fil-

Hz.

at

77.9

7

4.4

77

.O

79

.7

82.5

85.4

Encode

Disable

The
been

a nce

This

Guard

the
ter

checks

from

The

Q1003

and

circuit,

VDC)

is

at

the

plt"!gO

DISABLE)

rear

voltage

turning

88

.5

91

.5

94.8

97.4

100

.0

103.5

SERVICE

Encode

incorporated

id

a

for

circuit

encode

serviceman

distortion

without

the

radio.

Encode

a

Di.sabIe

Q1004.

positive

applj.ed

of

by

to

is

on

the

temporarily

p910-11

applied

both

707.2

110.9

114.8

118.8

123.0
t27 .3

Disable

as a maj-nten-

the

disables

cireuit

to make

and modulation

removing

circuit

To

disabte

voltage (+8.b

to Molex

radio.

jumperins

(A+).

to

the

Q1003

131.8

136.5

141

146.2

151

756.7

203.5

270.7

.4

162

I67

.3

t73

179

186

192

circuit has
servi

ceman

the Channel

and

allows

transrnit-
the

cover

consists

the

connector

This

is

pgto-9

positlve

Thls

base

of

and

2
o

8

o
2

8

.

encode

to

p910-b

accom-

(CG

e1003,

e1004.

of

14

CIRCUIT

ANALYSIS

LBIU1072

turned

\{hen

base of

the

off.

for

Output

preventing

With

Q1001

encocler

the

Stage transistor Q1002

any

When usinpr

cuit,

f

rom t

do

he opt
present)
on the

hookswitch

tion.

place

not
desk
This

microphone

will

ground,

the

to

radio through

the

rea r system

Both

protection

ity
ground

equipment.

The

lnputs

lead

battery

connector

ground

which

dently

through

will open

connected

oD,

Q1004

PTT Switch

off,

IC U1002

output.

tone

CAUTION

Encode

the

remove

rot

i ona

place

or

In station

CG

the

short

the

resulting

POWER

DISTRIBUTION

voltage

J910-1 and

connector

connected

are

diodes

is coupled

is connected

and

fusable

a

if the

A+

to

app1ies

+B'5

Q1001,

operating

the

and

Encode

is

Disable

microPhone

the

hookswi

t

monitor

the

in the

"uP"

aPPlications,

Switch

MON

[{ON

in

supply

possible damage

in

Position.

voltage

(A+)

J910-11

the

to

reverse

to

D901

and

through

to chassis

printed

ground

(see

wire

Figure

VDC to

forcing

voltage

Tone

removed,

r-

ci

(

t ch

i f

switch

posi-

do

the

on

to

connects

at the

IOC

boa

polar-

D9O2.

same

the

ring

wi

is acci-

2).

it

to

rd.

The

run

One battery

IOC boa

the
capacitor
stages.

P903-6

One

branch

through

one

and

switch

POWER On/Off switch controls

in
The other

to the

for the audio

RC-rippte

an

of the sections

S602.

input

rd through a

FL9OT

main board

The

voltage regulator
output

selected

Receiver

selection
either the

Tx

antenna

volt
relay

microphone,

sor

is fixed at

resistor
Schematic
instructions.

Regulated

8.5 volts i-s switched to

receiver or the Lransmitter

indica tor by the antenna

relay is also

regulated supply.

is

operated

by the

completing the

The

squelch circuit,

and

parls

of the

supplied directly

goes
the lransmitter

to

input

for two

amplifier

flller

(R642

of

other

U602.

section

The

8.5 volts

R640.

Refer

Diagram for resistor

powered

The

PTT

path

the audio

IF

amplifler

from the continuous

volt supply.

The receiver front-end, the

oscillator,

second

oscillator are supplied
Rx. The
exciter

are supplied from

21.4 MHz

the

transmitter

IF

stages and

oscillator and the

8.5

directly

from

feed-through

feeds

through

functions'

passes

C619)

and

POWER On/Off

of lhe

A+

the

regulator

means

by

relay

by

to

'

the

the

and

The

8.5

non-latching

switch on the

A-.

to

proces-

U502

are

8.5

receiver

the

8.5 V

from

V

Tx.

PA

to

ol

EATTERY

tcNrTtor

(OPTIOMLI

BATTERY

MIC ROPHONE

M IC ROPHONE

INTERCONNECT/OSC

(+}

5w

(-}

PTT

/ CG BOARD

PWR ON INOICATOR

M lC PRE

AUDIO PROCESSOR

I

TX

OSC CKTS

ON

A[4P

TRANSMIT/RECEIVE

RECEIVER

TRANSMITTER

CKTS

TRANSMIT INOICAIOR

EOARD

CKTS

Figure

2

Power Distribution

-

I

LBr37072

MAINTENANCE

PREVENTIVB I{A

To

from interrrlpting
electrlcal

checks as listed in

CONNECTIONS

should

tions to

INTENANCE

insure- bigh

parts

Ground

-

periodically

be

the

power

operating efficiency

system

at regular intervals,

the table of

source

operation. When ground
tery, the

checked for low
age drops

ELECTPTCAL

erator

economical

tery loses

week

tery

I4ECHANICAL

shock a nd vi bra

to mal<e

ANTENNA

clean

should

signal

connection

impedance. A

and alternator

sYsrEM

periodically

operating

water rapidly. usage

is acceptable

will

often

cause excessive noise

INSPECTION

t i

sure that

The

-

and free

become

antenna,

from

coated

will result.

check

-
to

for

on

,

nothing

dirt

or

operations,

routine

checks

to

and

This

Maintenance

MAINTENANCE CHECKS

Checks.

connections and connections

checked for tightness.

Loose

will cause excessive voltage

connections

from the battery

high

noise

voltage

the

keep

the

limits. over-voltage

batteries in

Since

-

check

antenna

for 1

is

working

or

corrosion.

mobile

poorly

are not made

to

impedance may

problems.

regulator

electrical

of 1 or

continuous

or

units

p1ugs,

oose

I oose

base

and

grounded,

vehicle

system

is

indicated

2

ounces

operation.

faulty

are

subject

nuts,

.

all

contacts

If

the antennas

loss

of radiation

prevent

mechanical

should

preventive

to

the voltage

poor

or

drops

directly

chassis

cause

and

excessive

alternator

within

of

when the

water

operation.

to constant

screws

should

or

made

be

maintenance

source

connec-

faulty

and

to the

must

bat-

be

volt-

gen-

or

safe and

bat-

per

ce1l

A

weak bal-

parts

and

kept

be

its

base

and

a weak

and

electrical

fail"ures

of all mechanical

should

per

o

Mon

x

x

X

include

lNTERVAL
t hs

Requi

and

the

AS

red

X

ALIGNMENT

checked

Refer

for

typica

FREQUENCY

quired
put

into

after.

DI

SA SS EI4BLY

The

-

periodically,

to

the applicable

transmitter

I voltage

CHECK

hy FCC.

Check

-
Normally,

operation,

To

service

receiver (Tx-Rx)

tvzo

screws
cover
Then
under

at

the rear

sl ide

tbe

control panel
To

service

the

two

radio
the

panel

screws

and

edge

and

sl

of the

lift

and

the alignment

ALIGNI{ENT

readings.

transmitter

these

after

the first

the

board,

securing

the

cover

edge

and

lift

IOC

the

at the

ide

the

.

off

receiver

and

ehecks

transmi

loosen

the

of the

out

of the

off.

board,

rear

cover

front

meter

PROCEDURE

"touched

frequency

are made

six

months

tler/

the

bottom

radio.

from

front

loosen

of

the

out from

control

readings

up"

and

and deviation

and

when necessary.

troubleshooting

when

the

once

should

as re-

unit

year

a

Be

careful
top
leads

boa rd .

To

remove

Remove

covers.

Remove

the
frame

panel.

be

sheet

is first

there-

are

when

as

connected

cover

the Tx-Rx

the

the

four

front panel

a nd

removi.ng

the

speaker

board:

top

screws

remove

to

and

to

the

x

x

the

the

bottom

securing

,,H,r

the

front

10

I NTENANCE

I{A

LBr:i1072

Remove the

ing the

Unsolder

and

screws.

Remove the

5.

RF shield.

the

remove

transistor

Turn the radio

the

copper

spacer

screw

hex

Driver transistor

Remove the

7.

Tx-Rx board

the

up

lift

erconnec

i nt

the

To remove

t i-frequency

mul

Remove tbe

t

In multi-frequency

move the

RF

the

J.

Remove the

shield.

the board
the board
interconrection

eight

screws

antenna

trto

the

screws

two

Q253.

and

over

Post,

from

washer

the

Q252.

9 sc rews

and

board

i

ons

t

the

off

.

ns

Pi

interconnect/

rd

boa

toP cover.

units,

five screws

12

screws

carefullY

and

up to

disconnect
pins.

secur-

connector

retaining

PA

the

in

remove

and

of

stud

securi

ng

carefullY

of the

;

t€-

securing

securing

lift

the

printed
part

circuit

the matching

of

included in the base

runs.
Tri-m

4.

the

new

required) lo
the removed transi

1et Ler

rrcrr

transistor a

lector

col

t ransistor lead

Apply

between

the

coa t of si

a

the mounting

spacer

the insulator

mounting surfaces of

the
the heat sink and
the spacer.
in the mounting
leads as shown

Diagrarn. Then

the transistor

board

translstor

the lead length

on the top

lso indicates the

(see

identifica tion

and to both sides

of

Place

hold the

runs

network

and

stor.

Figure

1 icon

surfaces of

and between

Q252

on both ends of

the transistor

hole.

on

the

and replace the

transistor mounting hardware,
using modera te
Newton

pounds)

1.0

screw

be

transistor

too

used.

meters

for M2.5 screw size and

(8

Nm

inch

post.

used for this adjustment

little

damage can result

or

torque of

(Nm)

pounds)

A torque

much

too

or

for the hex

wrench

because

collecLor
leads

(if

of

The

of the

3

for

.

)

grea

se

of

and

Q253

Align

the

Outline

of

body

0.6

6

inch

must

since

if

torque 1s

is

I]RIVER

The

tors used

-AND

stud

TRANSISTOR

PA

mounted

in the transmitter
Beryllium Oxide, a
If

the ceramic

is opened, crushed,

tion

abraded, the

i f inha

led .

transistors

To

replace

Q253:

1 . Rernove

2. Unsolder
50

watt

scribe or

the lead away

circuit

cool s.

Lift

out the transistor,
move the old
printed

sol deri

PULLTo.

taken

REPLACEMENT

WARNING

Power

RF

TOXIC

other

or

may

dust

Use

care

one

tYPe.

boa

lead at a

of this

PA RF transistors

Tx/Rx

soldering

substance.
encaPsula-

be

in

.

rd

iron.

X-actroo

from the

board

until

solder

circuit

ng tool

Special

prevent

to

board with a

such a s a

care

damage

Transis-

contain

broken

hazardous

rePlacing

Q252

time with

knife to

Printed

the solder

and

from

should

to the

or

Use

hold

SOLDA

and

re-

the

de-

be

b.

Solder

the
circuit
inner

edge of

solder the

transistor
care
that

not to use excessive heat

causes the

runs to Iift up
Check

for shorts and solder

leads to the

pattern.

Start

mounting

remaining length of

lead

to the board.

printed

from

printed

al the

hold and

Use

wire board

the board.

bridges.

CAUTION

Failure
leads as
the
could

may

a

a

7.

REMOVING

Removing ICrs

to solder the transistor

directed may result

generation

damage the transistor

cause

Replace

low

Tx/Rx

RF

of

power

output.

board and reassemble

radio.

!

}C

S

(and

loops

that

a1I other

in

or

soldered-in components) can be easily

accomplished by using a de-soldering

such as a

remove an

SOLDA PULLTo

IC,

heat each lead separately

or equivalent.

tool

To

on

the solder side and remove the old solder

with the de-soldering tool.

11

L8r31072

MAINTENANCE

o252

NARROW

LEAD

IS COLLECTOR

Figure

An a I ternate
special soldering
pins

simul taneously.

TEST AND TROUBLESHOOTING PROCEDURES

Maintenance of radio

use of the
servicing

Troubleshooting Charts

techniques

method

tip that

unique to this

is to

heats ali

is facilitated by

The Troubleshoot ing Chart is designed to

you

lead
or circuit.
provided
reference

rapidly to the

Typical

on the

when

Schematie

troubleshooting.

defective component

voltage

Diagram

3

- Q251
use a

of the

and

radio.

readings are

your

for

NARROW

LEAD

IS COLLECTOR

M2.

5 XB---=-

REW

SC

Lead Identification

signals

S

and

connectors on the

To

isolate a
determine loading
circuits, ete.

(plastic

or

appropriate

nector
paths

SQ

II{UTE

TEST POINTS

to

create an

that may be

HI,

filtered

nd SPKR HI

a

,

voltages

IOC

board.

signal or voltage

effects, loca

carefully insert

wand,

pins

toothpick)

of

the related

open circuit. Signals

isolated

volume

.

squelch

025 r

RC4?75

pass

include:

through

path

te short

an insulat-

between

Molex

Volume

HI, PTT,

the

to

the

con-

Rx

.t

I

'I

Troubleshooting

for most major

Transmi

the

tter/Receiver section of the

prob'lems

charts are

that

radio.

SFRVIClNG TECHNIQUES

The

high

modular radio lends itself

jsolation

and signal

Tp201

'TP2O2

TP203

Al{pL 1

TRIPLER

AMPL 3

TP251 AI{PL 4

12

cl.ensi ty

rpalfunctions

of

paths.

TRANSI',f

(Q201)

(Q202)

(Q204)

(Q251

plug-in

A

ITTER

Emitter Voltage

Base

Relative

Rela t i ve Out

)

might arise in

provided

desigr of the

well to

in the

rapid

voltage

majority of the

Voltage

Output

put

RF

section
poses

and

injection

An

RF

signal

monitor

Seven

eritical

operation.

They

TP351
TP401
TP501

Detector probes
are

available

to monitor

TP401

at

and the

probe

also is

the transmitter

test

circuit

points

locations

are as follows:

RECEIVER

Tripler

Receiver

455

kHz

Output

1st

oscitlator

IF

for

for alignment

the recei-ver

pur-

the lst receiver

2nd IF

at TP501.

available

frequency.

provided

are

to monitor

-

Q351

injection

to

al

MAINTENANCE LB131,O72

CAUT ION

iir

ri

il'

Before

bench

To

the

bench testing

power

protect

following input

supply.

the transmitter

radio

the

power

voltages must
Transrnitter unkeyed:
Transmitter
Transmitter

These voltages

take the

non-optimum load

voltage drop of

encountered in

Routine

transmitter
for loads
for transient

Many

commonly used bench

are

is for

practice,

0

to 6 amperes:

of

peaks

regulation and transient

keyed
keyed

specified

standard

"worst

the actual

tests should

short duration.

of

power

voltage suppression. Bench

force" regulation and filtering

automotive storage

battery.

be sure of the output voltage

output transistors from

not be exceeded:

20

Volts

(50

(no
at

case"

Input

resistive load):

ohm

load or non-resistive, load):

the normal vehicle

cables into

account.

conditions. For

limit

be

wiIl approach the

performed

voltages

battery

EIA

at

Standard

must not

antenna mismatches 1ikely

supplies cannot meet

may be usable

when operated in

characteristlcs

possible

18

Volts

terminals

The

voltage limits

18

instant

15.5

VoIt

Volts

of the radio

figure.

Test Voltages

exceed the limits

these requirements

supplies

which

parallel

of

destructi-on,

shown for

(13

shown

for

employ

with a

12 Volt

your

and

a

to be

VDC

even

load

"brute

r,t .

'/ui,:

GENEFAL

WORLo

ELECTRIC

COMPANY.

HEAOOUARTERS.

MOBILE

COMMUNICATIONS

LYNCHBURG. VIRGINIA 24502

DIVISION

U.S.A.

fradema.k ol

General

E lectric CompanV

PrintedinUSA.

U.S.A

GEN

ERA L@ ELEOTRIC

13

LBI3 LO72

A,*o'r,,rru

It3 FLAT

t PTACES

XASHER

,A Arpzeoszz

--COIIBI

NATION

II;IITPLATE

A

ArT

1

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