Kenwood Th-77a User manual

144/440(430)MHz

FM

DUAL

BANDER

TH-77A/E

SERVICE

MANUAL

KENWOOD

PRINTED

IN

JAPAN

B51-8057-00(B)1105

————

CONTENTS

DISASSEMBLY

FOR

REPAIR.........:cscssceccscssssesesesseessseessvess

2

CIRCUIT

DESCRIPTION

...ccscccsscsccssesssseecesecsesesseessesenseensssee

4

DESCRIPTION

OF

COMPONENTS.

......cccescccscsesssseecsseeeene

16

SEMICONDUCTOR

DATA.

......cccsscssssescecseccescessesssecrecsersese

20

PARTS

LIST....ccsccsscsocscscssecsssescsssccsseessseeees

Be

ete

tee

29

Antenna

DISASSEMBLY

............0...ccccccecccssccessesssceescecsesenseseeccceneneees

48

(790-0414-05)

PAGKING

250.

ei.cs0cg:hs

accaceligseralisedsiuvitdessangdaoucaseverbicecseeteor

49

ADJUSTMENT

.......cssccssssssccssecccscsccsscsssececsecsusceracsnseesncessese

50

PC

BOARD

VIEWS/CIRCUIT

DIAGRAMS

-%

VHF

VCO

(X58-3740-00)

...ccssscsucccossccessececsrsnscneesnecsrseecses

55

bi

nen

Wvar)

UHF

VCO

(X58-3760-00)..-cssssscsovessssesossevssssscersessessecocesss

56

|

(K29-4570-04)x2

APC

1K502077

0-00)

(AVS

itect

aks

ots

ce

canes

57

|

be

PI,

(H5B597.70-0G)

1B)

cscavtasceetsdesescssaestanoeetasncivtencbtehes

58

SUB-U

(X59-37

70-00):

(Chsscacsercescctevadvivervesissnasnasosavsersie

59

Knob

(ENCODER)

NOISE

AMP

(X58-3770-00)

(D).ccccsecccesssseecsseccessseecneeereee

60

ie

Neo

aeee

4)

AM

(X59-3810-00)

(B)

..ssssscsssssssesscsvecessecaressnessescneecenesssse

61

Knob

(SQL)

.

f

B00

MHz

(X59-3810-00)

(A)

.sessssssssesecesecesessscsseersessssensees

62

(K29-4571-04)

ee

eet

CONTROL

UNIT

(X53-333X-XX)..ssssesceeeessssseeseessceseeneeees

63

Pee

TX-RX

UNIT

(X57-3630-XX)

(REV)

.vscesssseeersvesseestsesseeeses

67

|

TX-RX

UNIT

(X57-3630-XX)

(RFU)

.scsccessecsesccsecsecersseessves

69

SCHEMATIC

DIAGRAM

u....ccsscssscsecccsssscsecsseseuseseecacceeseesee

71

BLOCK

DIAGRAM......cscssscsssessssscscsseccsessesecstesrsesseenssesseesses

77

——"

ee

lee

cores

LEVEL

DIAGRAM.................cccccccccereeseccecceccssessccceececerseesees

79

-0975-03):

K,

P,

M,

TERMINAL

FUNCTIONS

..0....ccsscssssscscccesssecssssessesssssseenseess

81

ep

a

ie

BC-9

(BATTERY

CHARGER)

..ccccccccsssscssscccsssssssssceveeessooe

82

BT-6

(AAA

MANGANESE/ALKALINE

BATTERY

CASE)

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

82

BC-10

(COMPACT

CHARGER).........cccscsesessssescesssssessesssees

83

cis

i

BC-11

(RAPID

CHARGER)

.........cccccscsscsosecsescssesceccucsseereees

84

wu

DC-4/5

(MOBILE

CHARGER)............ccscsceccscssesseceueeseesseres

89

BC-12

(WALL

CHARGER)........cccscsssssccsesesesssssessesssessseenees

89

HMC-2

(HEAD

SET

WITH

VOX

&

PTT)

...scscsssessssessesssees

90

Battery

ass’y

HS-7/8/9

(EAR

PHONE)

............::cccsccsecceeeeesecssteeneenseeesenens

92

PB-5/6/7/8

(Ni-Cd

BATTERY)

.....sccsscsscesecsssccctsesssssseessses

93

PB-9/10

(Ni-Cd

BATTERY)

....c.ccssccoscssecesecseecssscasssccsseeseess

94

PG-2W

(DC

CORD)/PG-3F

(CORD

WITH

PLUG)............

95

SC-28/29

(SOFT

CASE)

...cccccessscsessssssscececsessscsesseecasessecesess

96

WR-1

(WATERPROOF

CASE)

.......cccscscececesssssccseecesecsesssees

96

SMC-31/32

(SPEAKER

MICROPHONE)

...........:++e-02e000++-

97

Photo

is

TH-77A.

SMC-33

(SPEAKER

MICROPHONE).........0...ccssecsssssseesoee

98

eter

to

parts

list

on

page

29.

TSU-7

(CTCSS

UNIT)

cesccssccsssssccssssssssessssccsssesscsssseeeeveee

99

SPECIFICATIONS.

.........ccsssessssssseeeetessseeeceees

BACK

COVER

IA-ffA/E

DISASSEMBLY

FOR

REPAIR

1.

Removing

the

case

1)

Remove

the

three

screws

from

the

side

faces

of

the

case

@).

2)

Remove

the

four

screws

holding

the

bottom

plate

(@)

.

3)

Remove

the

cap

from

the

panel

(@).

4)

Pull

up

the

front

case

off

the

panel

side

(@).

NOTE:

This

should

be

done

carefully

so

that

the

FPC

cabling

in-

side

the

case

is

not

accidentally

cut.

2.

Removing

the

control

unit

1)

Pull

out

the

connector

(@).

2)

Remove

the

five

knobs

and

three

nuts

(@)

.

3)

Detach

the

clamp

by

removing

the

two

screws

(@)

.

4)

Remove

the

two

screws

holding

the

printed

board

(Q).

5)

Raise

the

contro!

board

by

inserting

a

slotted

screwdriver

between

its

underside

and

the

front

case.

NOTE:

The

FPC

should

not

be

pulled.

TH-77A/E

DISASSEMBLY

FOR

REPAIR

3.

Disassembling

the

control

unit

1)

The

panel

is

fastened

by

the

claws

of

the

sub-panel.

Raise

3)

Remove

the

volume

encoder

from

the

panel

by

holding

its

the

sub-panel

by

bending

the

two

claws

(@).

rear

edge.

2)

Turn

down

the

board

by

bending

another

two

claws

(@).

General

exploded

view

of

control

unit

4)

Overall

disassembly

should

be

made

by

following

the

order

@-~6@

as

illustrated

on

the

right.

4.

Assembling

the

control

unit

1)

Hold

the

sub-panel

as

shown

on

the

right

and

fit

it

inside

the

panel!

by

aligning

the

heads

of

MIC/SP

jacks

to

the

holes

in

the

panel.

2)

Push

the

PTT

knob

and

control

board

into

position.

3)

Screw

down

the

control

unit,

but

after

tightening

the

round

nuts

of

the

volume

encoder

(for

positioning

purpose).

TH-77A/E

CIRCUIT

DESCRIPTION

(1)

Frequency

Configuration

The

TH-77

has

independent

PLL

circuits

and

intermediate-fre-

quency

amplifiers

for

the

VHF

and

UHF

bands.

A

VHF

signal

and

a

UHF

signal

can

thus

be

received

at

the

sz.1e

time.

The

UHF

signal

can

be

received

at

the

same

time

as

the

VHF

signal

by

doubling

the

local

oscillation

frequency

for

the

VHF

band.

(See

Figure

1.)

The

received

VHF

single

is

converted

to

the

first

intermediate

frequency

(IF)

of

45.05

MHz

using

the

first

local

oscillator,

fre-

quency

of

181.05

to

219.05

MHz,

and

is

mixed

with

the

second

local

oscillator

frequency

of

45.505

MHz

to

produce

the

second

IF

of

455

kHz.

The

received

UHF

signal

band

is

converted

to

the

first

IF

of

58.525

MHz

using

the

first

local

oscillator

frequency

of

371.475

to

391.475

MHz,

and

is

mixed

with

the

second

local

oscillator

136-174

MHz

(E2)

144~148

MHz

(K,

P,

M,

X)

144~146

MHz

(T,

E1)

430-440

MHz

(M,

T,

X,

E1,

£2)

438~450

MHz

(K,

P)

|44MHz

BAND

136~174

MHz

('st

MIX

45.05MHz

136-174

MHz

192.475

MHz

202.475

MHz

384.95

MHz~404.95

MHz

430MHz

BAND

371.4

MHz

$

391.4

MHz

VHF

PLL

frequency

of

58.070

MHz

to

produce

the

second

IF

of

455

kHz.

The

local

oscillator

frequency

for

the

VHF

band

is

doubled,

when

the

UHF

signal

is

received

at

the

same

time.

The

UHF

signal

is

converted

to

the

first

IF

of

45.05

MHz

for

the

VHF

band

using

a

frequency

of

384.95

to

404.95

MHz

obtained

when

the

first

loca!

oscillator

frequency

of

192.475

to

202.475

MHz

for

the

VHF

band

is

doubled.

The

resulting

frequency

is

mixed

with

the

second

local

oscillation

frequency

of

45.505

MHz

to

pro-

duce

the

second

IF

of

455

kHz.

As

described

above,

signal

reception

for

the

VHF,

UHF,

or

sub-

UHF

band

is

based

on

a

double-conversion

system.

In

the

transmit

signal

channel,

a

directly

oscillated

voltage-controlled

oscillator

(VCO)

signal

for

the

VHF

and

UHF

bands

is

sent

to

the

reactance

modulator,

amplified

to

the

required

level

by

a

linear

amplifier,

and

transmitted.

455

KHz

455

KHz

12.8

MHz

REF

OSC

ae

MIC

AMP

(2.8MHz

Fig.

1

Circuit

configuration

by

frequency

In-//A/C

CIRCUIT

DESCRIPTION

(2)

Receive

Signal

Channel

The

TH-77

uses

common

antenna

for

the

VHF

and

UHF

bands,

so

it

has

an

internal

duplexer.

The

TH-77

also

incorporates

two

audio

amplifiers

for

internal

and

external

speakers.

(See

Figure

2.)

[

Item

Rating

Nominal

center

frequency

(fo)

45.050

MHz

Pass

bandwidth

fo

+7.5

kHz

or

more

at

3

dB

Attenuation

bandwidth

fo

+22

kHz

or

less

at

25

dB

Guaranteed

attenuation

80

dB

or

more

within

fo

+910

kHz

Spurious:

40

dB

or

more

Ripple

1.0

dB

or

less

Insertion

loss

4.0

dB

or

less

Terminal

impedance

8002/2

pF

Table

1

MCF

(L71-0409-05)

(TX-RX

unit

XF1)

—s

Item

Rating

Nominal

center

frequency

(fo)

Pass

bandwidth

58.525

MHz

fo

+8.5

kHz

or

more

at

3

dB

Attenuation

bandwidth

fo

+25

kHz

or

less

at

25

dB

fo

+70

kHz

or

less

at

60

dB

Guaranteed

attenuation

80

dB

or

more

at

fo

+910

kHz

Ripple

Insertion

loss

Terminal

impedance

Center

frequency

of

6

dB

bandwidth

(fo}

6

dB

bandwidth

40

dB

bandwidth

1.0

dB

or

less

4.0

dB

or

less

3802/3.5

pF

Table

2

MCF

(L71-0410-05)

(TX-RX

unit

XF201)

455

kHz+1.5

kHz

+7.5

kHz

or

more

+15

kHz

or

less

Ripple

Guaranteed

attenuation

1.5

dB

or

less

(455

kHz+1.5

kHz)

27

dB

or

more

within

fo

+100

kHz

Insertion

loss

6

dB

or

less

Terminal

impedance

Table

3

Ceramic

filter

(L72-0362-05)

(IF

unit

CF1,

CF2)

1.5

kQ

2-1

VHF

Receiving

Block

The

signal

from

the

antenna

is

passed

through

a

low-pass

fil-

ter,

a

duplexer,

and

antenna

switches

D4

(M1808)

and

D5

{MA77),

and

amplified

by

Q7

(2SK360).

The

unwanted

band

components

of

the

signal

are

eliminated

by

a

bandpass

filter.

The

resulting

signal

is

mixed

with

the

first

local

oscillator

fre-

quency

by

first

mixer

Q6

(2SC4083),

and

converted

to

the

first

IF.

The

unwanted

components

of

the

converted

first

IF

signal

are

attenuated

by

a

pair

of

MCFs

and

amplified

by

IF

amplifier

Q5

(2SC4619).

The

signal

is

then

input

to

1C2

(MC3372D).

The

input

signal

of

IC2

is

mixed

with

the

second

local

oscillator

fre-

quency,

and

converted

to

the

second

IF.

The

unwanted

com-

ponents

of

the

converted

signal

are

attenuated

by

a

ceramic

fil-

ter.

The

resulting

signal

is

amplified,

then

detected

by

a

quad-

rature

detector

to

produce

an

AF

signal.

2-2

UHF

Receiving

Block

The

signal

from

the

antenna

is

passed

through

a

low-pass

fil-

ter,

a

duplexer,

and

antenna

switches

D204,

D205

(M1808),

and

D206

(MA77),

then

amplified

by

Q207

(2SC4226).

The

sig-

nal

is

then

split

into

the

main

UHF

and

sub-UHF

bands

by

a

power

divider.

The

unwanted

band

components

of

the

signal

are

attenuated

by

a helical

filter.

The

resulting

signal

is

amplifi-

ed

by

0206.

The

signal

is

mixed

with

the

first

local

oscillator

fre-

quency

by

first

mixer

Q205

and

converted

to

the

first

IF,

and

the

unwanted

components

are

attenuated

by

a

pair

of

MCFs.

The

signal

is

then

amplified

by

IF

amplifier

Q210

(2SC4215),

and

in-

put

to

IC202

(MC3372D).

The

resulting

signal

is

detected

by

a

quadrature

detector

to

produce

an

AF

signal

in

the

same

way

as

in

the

VHF

receiving

block.

2-3

Sub-UHF

Receiving

Block

The

signal

from

the

antenna

is

input

to

the

UHF

receiving

block.

The

input

signal

of

the

UHF

receiving

block

is

amplified

by

Q207,

split

by

a

power

divider,

and

input

to

the

sub-UHF

receiv-

ing

block.

The

signal

amplified

by

Q201

(2SC4226)

is

passed

through

a

bandpass

filter

to

attenuate

unwanted

signal

compo-

nents.

The

signal

is

then

mixed

with

a

frequency

twice

the

first

local

oscillator

frequency

for

the

VHF

band

by

first

mixer

Q202

(2SC

4083),

then

converted

to

the

first

IF

for

the

VHF

band.

The

VHF

receiving

block

is

used

for

the

signal

flow

following

the

first

IF

signal.

The

collectors

of

the

first

mixers

for

the

sub-UHF

and

VHF

bands

are

placed

facing

each

other

to

prevent

the

first

mixers

being

influenced

by

other

bands

when

the

bias

is

turned

on

or

off.

IFI-/

(AE

CIRCUIT

DESCRIPTION

XX-XEEE-ESX

LINN

TOHLNOD

Mages

a

oso

(1907

puz

aun

eso

Se

SS

==

|

oso]

|

moves

|

r

71

|

Gus

Fs

xn

:

I

10249

eee

i

Zozol

ee

$020

01z0

102

4X

9020

9227

280

1v907

48,1

4HN

980

W907

ae

uz

(]

JHA

280

1v907

4,1

4HA

ae

|

[oso

sears

90

KHL

eH

a

HdWa

-

30

|

1495

|

eee

ren

so

(4x

2SO

W907

16.1

4HA

g929

eo7e2u

e227

42271

para

dA

ms

du

ANV

ad

|

W3LSAS

¥3AI3934

4HN

(nau)

Xx-0€9e-25X

ozo

eS

Spt

=

pape

ee

ey

ewe

Tsay

NT

gee

<

oee

|

(

!

|

West

SO

a

eee

(9)

XX-0226-89x

WALSAS

U3AIZ03H

JHA

ans

4ga

PPT

Ms

ANY

array

6

W3LSAS

43AI393Y

SHA

(Adu)

XX-O€9E-LSK

Hd

Fig.

2

RX

section

block

diagram

IA-f

fA/E

CIRCUIT

DESCRIPTION

2-4

Audio

Circuit

®

Outline

The

AFV

and

AFU

signals

that

are

deemphasized

in

the

trans-

mitting-receiving

unit

are

input

to

control

unit

IC3

(TC4066BF)

and

separated

into

the

main

signal

and

subsignal.

The

separat-

ed

signals

are

passed

through

high-pass

filters

and

input

to

IC4,

which

performs

speaker

selection

and

mix/separate

se-

lection.

The

resulting

signals

are

amplified

by

IC5

and

IC6

(NJM386BM)},

then

output.

2-4-1

CTCSS

and

DTSS

selection

Input

of

the

AFV

and

AFU

signals

to

the

CTCSS

unit

and

DTMF

decoder

is

switched

by

the

CBC

and

DTB

signals.

The

CBC

and

DTB

signals

are

unstable

when

the

CTCSS,

DTSS,

and

paging

functions

are

off.

Figure

3

shows

the

port

status.

2-4-2

Received

audio

signal

selection

The

audio

signals

for

the

VHF

and

UHF

bands

are

separated

in-

to

the

main

signal

and

subsignal

by

IC3.

IC3

opens

all

switches

for

muting

when

it

outputs

a

BEEP

pulse.

IC4

performs

speaker

selection

and

mix/separate

selection.

Figure

4

shows

the

port

status.

AFV

(VHF

AF)O

AFU

(UHF

AF}

O

ane

a

Fig.

4

RX

audio

switching

circuit

Sub

VOL

Main

VOL

CBC

DTB

(CTCSS

SW)

(DTSS

SW)

CTCSS

Unit

AFV

Decode

input

(VHF

AFIO

To

DTMF

Decode

IC

AFU

(UHF

AFIO

DTB

Fig.

3

CTCSS,

DTSS

switching

circuit

AF

CONTROL

Ic

4

©

EXT.

SP

*

When

the

normal

separate

mode

is

set,

the

subband

is

heard

on

the

internal

speaker

and

the

main

band,

on

the

external

speaker.

In-//A/CO

CIRCUIT

DESCRIPTION

2-4-3

External

speaker

detection

The

microcomputer

detects

that

the

REM

of

the

speaker

jack

is

zero

or

the

remote

switch

voltage

when

the

speaker

plug

is

inserted.

The

audio

input

is

then

switched

from

IC6

to

IC5

by

IC3.

2-4-4

Audio

amplifier

Amplifier

IC6

(NJM386BM)

is

used

for

the

internal

speaker,

and

amplifier

C5,

for

the

external

speaker.

The

power

for

IC6

and

IC5

is

produced

by

016

(2SB1182)

and

Q17

(2SC4617).

D4

(MA110)

and

O18

(DTA144WE)

are

a

power

on/off

control

cir-

cuit.

2-4-5

Squelch

circuit

Since

the

squelch

circuit

for

the

UHF

band

is

configured

identi-

cally

to

that

for

the

VHF

band,

only

the

squelch

circuit

operation

for

the

VHF

band

is

described

below.

The

detection

output

sig-

nal

of

C2

is

filtered

by

an

internal

amplifier

in

IC2.

The

noise

components

of

the

signal

are

amplified

by

013.

The

resulting

signal

is

rectified

by

D16

to

produce

a

squelch

signal.

The

volt-

age

at

the

input

of

Q11

is

turned

on

or

off

by

the

squeich

var-

iable

resistor.

The

SCV

signal

and

hysteresis

switches

are

acti-

vated

by

Q12.

2-4-6

Signal-strength

meter

circuit

The

TH-77

employs

signal-strength

meter

circuits

|C2

and

1C202

(MC3377D)

for

the

transmitting-receiving

unit.

For

the

VHF

band,

the

microcomputer

input

voltage

is

adjusted

by

VR1

of

the

transmitting-receiving

unit.

For

the

UHF

band,

it

is

ad-

justed

by

VR6

of

the

control

unit.

The

liquid-crystal

display

for

the

VHF

and

UHF

bands

appears

at

the

same

time.

Each

signal-

strength

meter

signal

is

thus

added

to

the

input

pins

of

differ-

ent

analog-to-digital

converters.

The

liquid-crystal

display

con-

sists

of

five

steps

in

a

pair

for

the

VHF

and

UHF

bands.

TH-77A/E

CIRCUIT

DESCRIPTION

(3)

Transmit

Signal

Channel

3-2

Drive

Circuit

and

Final-Stage

Amplifier

In

the

transmit

signal

channel,

a

directly

oscillated

voltage-con-

The

voltage-controlled

OUTBUTS

for

the

VHF

and

CHE

pends

ale

trolled

oscillator

(VCO)

signal

for

the

VHF

and

UHF

bands

is

sent

to

two-stage

amplifiers,

then

amplified

to

the

reaniied

sent

to

the

reactance

modulator.

The

output

levels

of

the

mi-

level

by

the

RF

power

amplifier

module.

The

amplified

output

crophone

amplifiers

for

the

VHF

and

UHF

bands

can

be

adjust-

signals

are

passed

through

the

antenna

switches

for

the

VHF

ed

independently.

(See

Figure

5.)

and

UHF

bands,

and

sent

through

a

duplexer

and

lowpass

filter

3-1

Modulator

Circuit

to

the

antenna.

The

audio

signal

from

the

microphone

is

sent

to

control

unit

!C1

(NJM4560M),

then

a

preemphasis

circuit,

amplifier,

limiter

am-

plifier,

and

splatter

filter.

The

signal

is

then

selected

for

the

VHF

and

UHF

bands

by

Q12.

The

frequency

deviation

can

be

adjust-

ed

by

VR3

and

VR4.

The

modulation

signal

is

applied

to

a

vari-

cap

diode

for

voltage-controlled

oscillator

modulation

for

the

VHF

and

UHF

bands,

then

sent

to

the

reactance

modulator.

The

input

pins

are

jumpered

by

Q11

when

a

dual-tone

multifre-

quency

(DTMF)

is

used.

144

MHz

band

430

MHz

band

Low

frequency

VCO

(VHF)

Buffer Buffer

Excitation

esis

25238

(KI)

rae

oe

sao

(ee

SAva24

NJM4560M

284083

28C4083

2SCA215

2SC3356

S-AV22A

Buffer

amplifier

2S8C4215

PLL

eu

amplifier

M56760FP

2SC4116

CPU

#PD751

|6GF

HD404608

PLL

M56760FP

Buffer

amplifier

28C4226

REF

OSC

2804116

UH

Buffer Buffer

Excitation

Power

VCO(UHF)

amplifier

amnpihe

2SKSOBNV

(K52)

2804226

284226 284226

2sc4093

§-AU26

Fig.

5

Transmitter

system

block

diagram

T

10

H-77A/E

CIRCUIT

DESCRIPTION

3-3

APC

Circuit

The

automatic

phase

control

(APC)

circuit

produces

attain

a

stable

transmission

output.

This

circuit

also

detects

the

current

of

the

final-stage

amplifier

and

controls

the

input

power

level

of

the

amplifier.

ee

L

Table

4

The

APC

circuit

operation

for

the

UHF

band

is

explained

below

(Figure

6).

During

transmission,

04

is

turned

on

by

the

5TV

and

5TU

signals,

and

IC1

is

activated.

The

output

power

of

IC101

is

detected

as

the

voltage

drop

across

R4

and

R5.

The

voltage

at

both

ends

of

D1,

whichis

completely

stabilized

by

the

constant

current

source

of

01,

is

compared

with

the

voltage

divided

by

VR1,

R11,

and

VR2.

The

current

flowing

through

D101

is

con-

trolled

so

that

no

voltage

difference

occurs.

Consequently,

the

drive

input

power

of

|C101

decreases

when

the

power

amplifi-

er

module

current

increases,

and

the

drive

power

increases

when

the

module

current

decreases.

For

high-,

middle-,

and

low-level

selection,

Q2

and

Q3

are

turned

on

then

off

when

the

H/L1

and

H/L2

ports

are

con-

trolled.

The

reference

voltage

for

!C1

is

then

switched.

(See

Table

4.)

O

HA2

H/LI

STV

Fig.

6

APC

circuit

O

STU

Ic

101

Q2,93

Q7,Q98

Ql

Q4

1cl

R4,R5

UHF

Power

Amplifier

BAND

SW

UHF

POWER

SW

VHF

POWER

SW

CONSTANT

CURRENT

SOURCE

APC

AMP

SW

OC

ERROR

AMP

CURRENT

DETECT

IH-//A/E

CIRCUIT

DESCRIPTION

(4)

Power

Supply

Circuit

External

power

is

always

supplied

to

1C8

and

IC13.

The

[C8

out-

put

is

sent

to

1C10

and

IC12.

Therefore,

the

current

for

IC8

and

1C13

and

the

microcomputer

backup

current

flow

when

the

power

is

turned

off

with

the

battery

connected.

The

PW

port

of

IC10

is

made

low

when

the

power

is

turned

on.

Q20

(1/2)

is

then

turned

on.

As

a

result,

a

reference

voltage

is

applied

to

each

regulator.

Power

is

supplied

to

the

CTCSS

unit

when

Q20

(2/2)

is

turned

on.

(See

Figure

7.)

The

5C

and

5R

signals

are

produced

by

Q5

and

Q6.

A5T

signal

is

produced

by

Q8

and

Q9.

The

5C,

5R,

and

5T

signals

are

dis-

tributed

by

each

switch.

The

reference

OSC

power

for

the

phase-locked

loop

(PLL)

circuit

is

supplied

from

the

5C

signal.

The

5RV,

SRVC,

and

5CV

signals

are

turned

on

during

VHF

re-

ception.

The

5RU, 5CU,

and

5RU

signals

are

turned

on

during

UHF

reception.

The

5TV

and

5TU

signals

are

turned

on

accord-

ing

to

the

band

in

use

during

transmission.

(5)

Save

Circuit

Q7

is

controlled

by

the

SAVE

of

1C10.

The

5C

and

5R

regula-

tors

of

Q5

are

then

turned

on

or

off

to

reduce

the

mean

current

consumption.

The

automatic

power-off

(APO)

function

inter-

rupts

all

power

supplies

to

circuits

except

the

microcomputer

by

turning

off

Q20.

APO

operation

thus

results

in

the

much

the

same

current

consumption

as

when

the

power

is

off.

d

SRUC

SRV

SCV

SRVC

sRU

ice

scuU

S-

812506

STV

Ic10,

1c

12

Q20

2/2

Fig.

7

Power

supply

circuit

11

IA-/7A/E

12

CIRCUIT

DESCRIPTION

(6)

PLL

Circuit

The

oscillator

circuit

consists

of

reference

oscillators

with

inde-

pendent

phase-locked

loop

(PLL)

and

voltage-controlled

oscil-

lator

(VCO)

circuits

for

both

the

VHF

and

UHF

bands.

The

oscil-

lator

frequency

is

sent

to

the

V/U

PLL

IC.

6-1

PLL

The

12.8-MHz

crystal

oscillator,

X202,

is

oscillated

by

Q211.

The

oscillation

output

is

sent

to

1C201

and

Q212,

and

the

out-

put

signal

of

212

is

sent

to

C1.

The

reference

oscillation

fre-

quency

is

divided

by

IC1

(VHF)

and

IC201

(UHF)

to

produce

a

reference

frequency

of

5

kHz

or

6.25

kHz.

The

VCO

output

of

the

comparison

frequency

is

amplified

by

Q2

(VHF)

and

Q202

(UHF),

then

divided

by

pulse

swallow

PLL

circuits

IC1

and

IC2.

PLL

synthesizers

with

5-,

10-,

12.5-,

15-,

20-,

and

25-kHz

steps

are

established

by

comparing

the

phase

of

the

X201

crystal

oscillator

frequency

with

that

of

the

divided

reference

frequency.

6-2

VCO

The

desired

frequency

is

produced

by

direct

oscillation

by

a

Colpitts

oscillator

circuit

consisting

of

VCO-V

(X58-3740-00),

VCO-U

(X58-3760-00),

and

field-effect

transistor

(FET)

02.

The

VCO

control

voltage

is

applied

to

varicap

diodes

D1

and

D2

to

change

the

oscillation

frequency.

During

reception,

the

T/R

is

made

high,

and

Q1

and

D4

are

turned

on.

The

oscillation

fre-

quency

is

then

switched.

VCO-U

makes

the

T/R

low

during

reception

and

turns

Q1

and

D3

off

to

select

the

range

of

the

os-

cillation

frequency.

+5V

5CU

|

x58-3760

Q3

RF

Amp

RF

Amp

Q208

Switching

6-3

Unlock

Detector

Circuit

When

the

PLL

circuit

is

in

the

unlock

mode,

the

pulses

output

to

the

LOCK

pins

(pin

13)

of

IC1

andiC201

are

waveform-shaped

by

R6

and

C7

for

the

VHF

band

and

R205

and

C208

for

the

UHF

band.

The

UL

is

then

amde

high.

The

voltage

at

the

UL

is

detected

by

the

microcomputer

to

select

the

transmitter

or

the

receiver

and

contro!

the

timing.

R6/R205

to

p-com

ULU

C7/C

208

a].f

Fig.

9

Uniock

Detector

Circuit

fi

fl

a

uy,

-#—-

VHF

12.8MHz

to

Xin

12.8

|

2]

CPS

12.}8MHz

date

RST

;

XOUT

|

14

H

Q202

OUT

P

OO)

RF

'

Amp

13

Unlock

OUT

Driver

Detection

or

Mixer

1c201

M56760FP

MOD

OD

MIC

Amp

12

O

TXU

Sscu-6

Fig.

8

PLL

circuit

(UHF)

TH-77A/E

CIRCUIT

DESCRIPTION

(7)

Microcomputer

and

Peripheral

Circuits

7-1

Reset

and

Backup

Circuits

changes

the

output

signal

from

high

to

low.

The

microcomput-

Alow

pulse

of

approximately

1

ms

duration

is

output

from

reset

er

enters

the

backup

mode

when

microcomputer

port

INT4

is

circuits

C76

and

Q19

when

the

B

power

is

turned

on.

Micro-

made

low.

Microcomputer

[C12

is

reset

by

microcomputer

computer

|C10

is

then

reset.

When

the

B

power

is

turned

off,

IC10.

voltage

detector

circuit

C9

detects

the

5-V

line

drop

and

Power

SW

Power

SW

ON

OFF

SV

B

0

!

0

t

INT

4]

5VF

fees

Voltage

fo)

Timing

chart

Ic9

VOLTAGE

DETECTOR

Fig.

10

Reset

and

backup

circuit

13

IA-ff7A/E

14

CIRCUIT

DESCRIPTION

7-2

DTMF

and

DTSS/PAGING

7-2-1

DTMF

encode

A

DTMF

signal

is

directly

produced

using

the

TOR

and

TOC

signals

of

IC12.

The

frequency-response

characteristic

of

the

DTMF

signal

is

compensated

for

by

C58,

R48,

and

VR5.

The

re-

sultant

DTMF

signal

is

level-adjusted,

then

input

to

3

of

C1.

The

DTMF

monitor

signal

is

sent

to

the

input

pins

of

the

main

and

sub

high-pass

filters.

The

audio

frequency

is

muted

by

IC3.

7-2-2

DTMF

decode

The

AFV

and

AFU

signals

are

split

up

and

sent

to

the

CTCSS

unit

and

DTMF

decoder

by

IC2,

then

sent

to

C11.

C11

outputs

the

code

corresponding

to

the

DTMF

signal

from

pins

11

through

14.

The

output

code

is

compared

with

the

DTSS

and

PAGING

codes

by

IC10,

which

determines

whether

they

match.

7-2-3

DTMF

decode

timing

The

main

band

and

sub-band

are

activated

by

one

DTMF

de-

coder.

For

a

single

band,

only

the

main

band

is

checked.

For

a

dual

band,

the

DTMF

decoder

is

switched

into

the

band

carry-

ing

a

BUSY

signal

to

check

the

band.

The

other

band

may

not

be

checked

when

a

BUSY

signal

is

carried

in

the

main

band

and

sub-band

at

the

same

time.

5M

ENCODER

ENDP

ENCP

MPU

IC10

DTMF

DECODE

Fig.

11

Key,

Encode

input

circuit

7-3

LED

Drive

Circuit

The

LMP

of

IC12

is

made

high

when

the

lamp

switch

is

pressed.

The

constant-current

circuit

consisting

of

D7,

Q21,

and

R116

is

then

turned

on.

As

a

result,

a

constant

current

(40

mA)

flows

through

the

LED

even

if

the

supply

voltage

fluctu-

ates.

Fig.

12

Lamp

circuit

MPU

!C305

IA-/7A/E

CIRCUIT

DESCRIPTION

7-4

Remote

Control

Microphone

Circuit

The

remote

control

microphone

circuit

has

two

internal

audio

amplifiers.

The

external

speaker

is

directly

connected

to

IC5

via

the

AFO

pin.

The

speaker

microphone

and

speaker

plug

con-

nections

are

detected

using

the

REM

and

MDT

signals.

The

ICS(CONTROL

UNIT)

AFO

sp

MIC

AMP

REM

and

MDT

signals

are

made

high

when

the

speaker

micro-

phone

and

speaker

plug

are

not

connected.

The

REM

and

MDT

signals

are

then

output

from

IC6

to

the

internal

speaker.

An

au-

dio

signal

is

output

to

the

external

speaker

when

the

MDT

or

REM

signal

is

set

low.

EXTERNAL

SPEAKER

EXTERNAL

MIC

tOpF

(32)

(*1)

Voltage

appears

from

the

internal

M5

line

(5

V)

via

R2.

(*2)

In

the

capacitor

is

not

required.

Make

the

connection

directly.

@

|n

the

case

when

a

capacitor

to

cut

DC

voltage

is

con-

nected

to

the

external

device

@

In

the

case

when

a

two-terminal

condenser

micro-

phone

is

used

as

the

external

microphone

Fig.

13

Speaker,

Microphone,

Remote

circuit

7-5

CTCSS

Operation

The

CTCSS

in

the

main

band

and

sub-band

is

checked

by

the

CTCSS

timing

unit.

Only

the

main

band

is

checked

when

a

single

band

is

used.

The

band

carrying

a

BUSY

signal

is

checked

when

a

dual

bandis

used

with

the

main band

and

sub-

band

CTCSS

set

on.

The

main band

and

sub-band

are

checked

every

500

ms

when

they

carry

a

BUSY

signal.

During

full-du-

CTCSS

CHECK

TIMING

(MAIN,

SUB

CTCSS

ON)

plex

operation,

the

CTCSS

in

the

main

band

outputs

a

subtone

when

the

TONE

and

CTCSS

signals

are

on.

Turns

the

CTCSS

in

the

subband

cannot

be

checked.

In

that

case,

the

squelch

in

the

subband

is

opened

or

closed

using

only

the

BUSY

signal.

For

the

band

in

which

the

CTCSS

cannot

be

checked,

the

“CT”

display

disappears

only

during

transmission.

i

OFF

|

| |

|

(iT

(CLOSE)

ON

|

S.

BUSY

OFF

ctcss

MAIN

UNIT

yp

—

L_Y

U

J

500ms

Fig.

14

CTCSS

timing

chart

15

IA-/fA/E

1.

Control

Unit

(X53-333X-XX)

Reference

No.

Function

Q1

5RUC/S5RUOM

switch

Q2

5RV/5CV

switch

5RVC/5RU

switch

5RVOM/5CU

switch

5C/5R

AVR

Device

Functions

Description

5RUC:

Power

switch

in

the

stage

after

the

UHF

receiver

mixer

5RV:

VHF

receiver

RF

amplifier/mixer

power

switch

5CV:

VHF

PLL

power

switch

5RVC:

Power

switch

in

the

stage

after

the

VHF

receiver

mixer

5RU:

UHF

receiver

RF

amplifier

power

switch

5RVOM:

Subband

UHF

receiver

power

switch

5CU:

UHF

PLL

power

switch

5C/5R

AVR

error

amplifier

Save

operation

switch

5T

AVR

5T

AVR

error

amplifier

5TV

switch

Microphone

input

shorting

switch

The

amplifier

is

turned

on

when

Q7

is

turned

on

or

off.

1/2:

Off

during

save

operation.

2/3:

On

during

transmission.

The

amplifier

is

turned

on

when

Q7

is

turned

on

or

off.

On

during

VHF

transmission.

On

while

DTMF

signa!

is

modulated.

Modulation

output

band

switch

CTCSS

input

selection

control

Main

audio

high-pass

filter

Sub-audio

high-pass

filter

AF

amplifier

regulator

AF

amplifier

regulator

AF

regulator

switch

On

when

AF

signal

is

output.

Microcomputer

reset

switch

5M/CTCSS

power

switch

Lamp

LED

constant-current

source

foa2

|

aatswitch

|

On

when

lamplights

[023

|

DTM

decoder

input

selection

control

|

[01

|

Power

reverse-connection

protection

diode

|

[02

|

AFIC

BY

pinvottage

drop

prevention

|

[03

|

AFIC

BY

voltage

drop

prevention

|

[D4

|

AFICAVR

time-constantcontrol

[05

|

AFICBY

pinreverse-tiow

prevention

|

Df

ee

Dae

age

re

ee

Pi

Oe

ee

Low

for

1

ms

when

external

power

is

supplied.

1/2:

Power

circuit

reference

voltage

on/off

2/2:

On

during

CTCSS

operation.

|

Ds_____|

Microcomputer

backup

battery

selection

[D8

|

BacklightteD

D9

Backlight

LED

Backlight

LED

Backlight

LED

Backlight

LED

Backlight

LED

—

Electrostatic

surge

absorption

Microphone

amplifier

DTMF/CTCSS

decode

selection

Selection

of

AF

signal

to

main

band

and

sub-band

Selection

of

AF

signal

to

internal/external

AF

amplifier

External

audio

power

amplifier

Connected

to

external

speaker

socket.

Internal

audio

power

amplifier

Connected

to interna!

speaker.

16

IH-77A/E

Device

Functions

Reference

No.

Function

Description

Cross-band

repeater

AF

switch

AF

output

signal

in

sub-band

is

input

to

microphone

amplifier.

5-V

regulator

Used

for

microcomputer

and

power

circuit

reference

voltages.

Backup

detection

Microcomputer

Power

and

signaling

control

DTMF

decoder

IC

Microcomputer

Display,

key

entry,

and

DTMF

signal

generation

CTCSS

unit

power

17

IH-77A/E

18

Device

Functions

2.

TX-RX

Unit

(X57-3630-XX)

Reference

No.

Function

Description

VCO

ripple

filter

amplifier

PLL

buffer

amplifier

VHF

driver

initial

stage

VHF

driver

final

stage

Output

level:

14

to

15

dBm

(typical)

IF

post-amoplifier

VHF

receiver

mixer

VHF

receiver

amplifier

Power

switch

Air

band

is

on.

AMR

band

is

off

Power

switch

Power

switch

Sub-UHF

power

Squelch

switch

Turned

on

or

off

using

noise

detection

output

signal.

1

Squeich

and

hysteresis

switches

Turned

on

or

off

using

output

signal

of

Q11.

Q13

Noise

amplifier

VCO

ripple

filter

amplifier

PLL

buffer

amplifier

UHF

driver

initial

stage

Q204

UHF

driver

final

stage

Output

level:

12

to

13

dBm

(typical)

UHF

receiver

mixer

UHF

receiver

amplifier

second

stage

Q207

pertsc,

eamaniieie

ee

Poon

|

Pil

releonee

ont

Sd

oat

|

Pt

retenco

ouput

viF

buferergii

[|

___—

Se

ee

a

foe)

vetonttesbebanaeh

=k

:

ee

Peo

ee

a

ee

fos

|

Amternaswiten

Pd

Dg

UHF

receiver

amplifier

initial

stage

360/800

daughter

power

switch

360/800

daughter

power

switch

2

6

AGC

control

diode

D10

Receiver

filter

band

shift

Receiver

filter

band

shift

D12

Receiver

filter

band

shift

D13

D16

D1i5

Power

switch

reverse-current

prevention

D201

Ripple

filter

speed-up

IC2

input

voltage

control

(for

air

band)

Sub-UHF

power

reverse-current

prevention

Squelch/noise

detection

VCO

output

selection

switch

Driver

final-stage

bias

D207

D208

D209

D202

D203

D204

Antenna

switch

D205

Antenna

switch

D206

Antenna

switch

VCO

output

selection

360/800

power

line

reverse-current

prevention

D210

Mixer

input

selection

switch

UHF

power

line

reverse-current

prevention

0211

TH-77A/E

Device

Functions

Function

Mixer

input

selection

switch

D212

Sub-UHF

power

line

reverse-current

prevention

D213

Receiver

block

high-input

protection

D214

VCO

output

selection

switch

360

input

selection

switch

VCO

output

selection

switch

VHF

PLL

circuit

VHF

FM

IF

system

circuit

VHF

RF

power

amplifier

module

UHF

PLL

circuit

Daughter

Reference

No.

Description

UHF

FM

IF

system

circuit

1

Unit

(X58-3770-00)

Function

APC

constant-current

source

UHF

mid-power

setting

voltage

switch

Jumpers

VR1.

Jumpers

R11

and

VR1.

Turned

on

using

5TV

and

5TU

signals.

UHF

low-power

setting

voltage

switch

APC

error

amplifier

power

switch

Band

selection

switch

(UHF)

Turns

the

setting

voltage

on

or

off

with

a

variable

resistor.

Band

selection

switch

(VHF)

Turns

the

setting

voltage

on

or

off

with

a

variable

resistor.

Q?

VHF

mid-power

setting

voltage

switch

Jumpers

VR3.

Q

VHF

low-power

setting

voltage

switch

Jumpers

R19

and

VR3.

Q201

Q202

Sub-UHF

RF

amplifier

Sub-UHF

mixer

;

a

D

High/Middle/Low

selection

a301

UHF

squelch

noise

amplifier

(7a

ere

eared

Eee

5TV/STU

reverse-current

prevention

UHF

APC

ATT

diode

Amplifier

high-input

signal

protection

Daughter

UHF

noise

detection

UHF

power

amplifier

module

APC

error

amplifier

2

Unit

(X59-3810-00)

Description

Reference

No.

Function

Qi

800

RF

amplifier

Q2

Local

oscillator

doubler

Mixer

AGC

level

shift

Air

band

AF

amplifier

FM

discrete

short-circuit

AM

receiver

circuit

19

TH-77A/E

SEMICONDUCTOR

DATA

Microcomputer

HD404608A71H

(Control

Unit

IC12)

@Pin

Functions

|

ow

wi

co

+tONe

Ne

B99

e886.

555808

SSSSLOOSELESSS5O550RH

TET

TTT

te

a

th

gee2fe2rereeRRreresssesssesas

Da}

|}

so|

|

SEG30

Ds

{_|2

ss|_|

SEG29

De|

|3

s8{_

|

SEG28

D7[

|4

87}

|

SEG27

De|

{5

se{

|

SEG26

Ds|

|6

OS

55]

|

SEG25

Dio{

|7

s4|

|

SEG24

VC

ret/Dii

|_|]

8

s3|_|

SEG23

COMPO/Di2

|_|

s2|_|

SEG22

COMP1/Di3

[

_|

10

51|

|

SEG21

TEST

HD404608A71H

so]

SEG20

X1

[

]

12

49|_

|

SEG19

X2]

|

13

48{

|

SEG18

GND

14

47{_|

SEG17

SCK/ROo

[_|

4s{_|

SEG16

SV/RO1

|_|

16

45}

|

SEG15

SO/RO2

|_|

17

4s{

|

SEG14

ROs

[_|

18

«||

SEG13

Rio

|

19

42{_|

SEG12

R11

|

20

a1{

|

SEG11

aNSRSZ&RRBRRBSRSEBRBKBSKBBSE

BBS

TLELLELLCELE

LLL

LL

LLL

LL

Lg

nO

oOo

=

iy]

-

WN

v

SEGARA

ABSSBSRRKRTOSHRRRS

GkEeceee

eee

ogee

ooo

CIEE

VHHHHNHDOU

=|z\z

e

20

Kenwood TH-77A User manual

Popular Transceiver manuals by other brands