Onkyo TX-7230 Manuale utente

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SERVICE

MANUAL

QUARTZ

SYNTHESIZED

|

TUNER

AMPLIFIER

MODEL

TX~7230

Silver

and

b:

SAFETY-RELATED

COMPONENT

WARNING!!

COMPONENTS

IDENTIFIED

BY

MARK

Z\

ON

THE

SCHEMATIC

DIAGRAM

AND

IN

THE

PARTS

LIST

ARE

CRITICAL

FOR

RiSK

OF

FIRE

AND

ELECTRIC

SHOCK.

REPLACE

THESE

COMPO-

NENTS

WITH

ONKYO

PARTS

WHOSE

PARTS

NUMBERS

APPEAR

AS

SHOWN

IN

THIS

MANUAL.

MAKE

LEAKAGE-CURRENT

OR

RESISTANCE

MEASUREMENTS

TO

DETERMINE

THAT

EX-

POSED PARTS

ARE

ACCEPTABLY

INSULATED

FROM

THE

SUPPLY

CIRCUIT

BEFORE

RETURN.

ING

THE

APPLIANCE

TO

THE

CUSTOMER.

i

mocels

TABLE

OF

CONTENTS

Spectiications

.

00

ce

ee

oe

2

Service

procédures...

2s

ee

poe

ee

3

Biock

diagrani

Amplifier

section.

«2.

ee

eee

4

Power

supply

section.

2...

0.

ee

4

Dynaznic

bass

ciretitusc0..

oo

oe

oe

4

Pune?

section)

oe

ee

5

Exploded

view.

2.22

ee

ee

6

Paris

list.

0

ee

ee,

Gy

ees

7

Circuit

description.

oe

ee

oe

8

Adjustment

procedures...

65.

oe

13

Pcb

view/list

Tuner

section

2

0.

ee

ee

ee,

15

Digital

section.

6.

ee

bye

ee

17

Aimplifier

section...

oe

21

Control

section...

ee

ee

25

Senematic

diagram

Jumer

section

3.

2k

eee

oe

19

AMD,

section

4.

lee

ee

ee,

2.

Block

diaprani

of

1Co

0

ee,

head

Packing

View.

2.

0

See

ee

ee.

2

TX~7230

SPECIFICATIONS

AMPLIFIER

SECTION

Power

Output:

Musical

Power

Output:

Continuous

Power

Output:

Total

Harmonic

Distortion:

IM

Distortion:

Damping

Factor:

Frequency

Response:

RIAA

Deviation:

Sensitivity

and

Impedance:

Phono

Overload:

Signal-to-Noise

Ratio:

Tone

Controls:

Loudness

(—30dB):

Subsonic:

TUNER

SECTION

FM:

Tuning

Range:

Usable

Sensitivity:

50dB

Quieting

Sensitivity:

Capture

Ratio:

Image

Rejection

Ratio:

IF

Rejection

Ratio:

Signal-to-Noisc

Ratio:

Selectivity:

AM

Suppression

Ratio:

Harmonic

Distortion:

Frequency

Response:

Stereo

Separation:

Tuning

Level(Hi/Lo):

Muting

Level:

Stereo

Threshold:

AM:

Tuning

Range:

Usable

Sensitivity:

Image

Rejection

Ratio:

IF

Rejection

Ratio:

Signal-to-Noise

Ratio:

Harmonic

Distortion:

GENERAL

Semiconductors:

Dimensions

(WX

HXD):

Weight:

40

watts

per

channel,

min

RMS,

at

8

ohms,

both

channels

driven,

from

20Hz

to

20kHz,

with

no

more

than

0.04%

THD.

2

x

85

watts

at

4

ohms,

1kHz

(DIN)

2

X

55

watts

at

8

ohms,

1kHz

(DIN)

2

x

55

watts

at

4

ohms,

1kHz

(DIN)

2

x

40

atwatts

ato

at

8

ohms,

1kHz

(DIN)

0.08%

at

rated

power

0.08%

at

1

watt

output

0.08%

at

rated

power

0.08%

at

1

watt

output

35

at

8

ohms

20

—

30,000

Hz

+

1

dB

20

—

20,000

Hz

+

0.8dB

Phono:

2.5mV/50

kohms

CD/Tape

Play:

150mV/50

kohms

Tape

Rec:

150mV/3.5

kohms

(phono)

180mV

RMS

at

1

kHz,

0.04%

THD

Phono:

85dB

(at

10mV

input,

A

weighted)

76dB

({HF

A-202)

CD/Tape:

95dB

(A

weighted)

80dB

(IHF

A-202)

Bass:

+

10dB

at

100Hz

Treble:

+

10dB

at

10kHz

+7

dB

at

70

Hz,

+5

dB

at

10kHz

~—6

dB

at

15

Hz

87.5

—

108.0

MHz

(SOkHz

steps)

Mono:

12.8dBf,

1.2uV,

75

ohms

1.0uzV

(S/N

26dB,

40kHz

Devi.)

75

ohms

DIN

Stereo:

18.0dBf,

2.2uV,

75

ohms

23uV

(S/N

46dB,

40kHz

Devi.)

75

ohms

DIN

Mono:

18.0dBf,

2.2uV

75

ohms

Stereo:

37.2dBf,

20uV,

75

ohms

1.5dB

85dB

90dB

Mono:

71dB

Stereo:

66dB

50dB

DIN

(+300kHz,

40kHz

dev.)

50dB

Mono:

0.15%

Stereo:

0.3%

30

—

15,000Hz

+

1.5dB

40dB

at

1kHz

30dB

at

100

—

10,000Hz

17.2dBf,

2uV

17.2dBf,

2uV

§22

—

1611kHz

(9kHz

steps)

30uV

40dB

40dB

40dB

0.8%

FETs:

7

TR:

37

ICs:

10

Diodes:

54

LEDs:

28

435

x

112

X

343

mm

17-1/8”

x

4-7/16”

X

13-1/2”

7.8

kg

17.2

Ibs.

Specifications

and

features

are

subject

to

change

without

notice.

SERVICE

PROCEDURES

1.

Replacing

the

fuses

For

continued

protection

against

fire

hazard,

replace

only

with

same

type

and

same

rating

fuse.

Circuit

no.

Partsno.

Description

F501,

F601

252076

3.15A-SE-EAK,

Primary

F902

252074

2A-SE-EAK,

Primary

F903,

F904

252078

5A-SE-EAK,

Secondary

F905

252070

1A-SE-EAK,

Secondary

‘2.

Replacing

the

lamp

This

unit

uses

the

lamp

listed

below.

Circuit

no.

Partsno.

Desciption

PL901

210064A

PL

6.3V,

250mA,

Dial

plate

illumination

3.

Removement

of

display

pc

board

@.

Remove

the

five

screws

holding

the

top

cover

and

chassis

(side

bracket:4

back

panel:

1),

and

remove

the

top

cover.

Remove

the

five

screws

holding

the

front

panel

and

front

bracket,

and

remove

the

front

panel.

Remove

the

two

screws

holding

the

switch

pc

board

and

front

bracket,

and

remove

the

switch

pc

board

of

U4.

Remove

the

four

screws

holding

the

holder

and

front

bracket.

Remove

the

display

pc

board

ass’y

from

the

four

nails

of

holder,

and

remove

the

holder.

Remove

the

two

knobs

(A805).

Remove

the

two

screws

holing

the

NAAF—2306

pc

Board

ass’y

and

center

bracket,

and

remove

the

NAAF—2306.

©

e

SO:

2.

@

dynamic

bass

expander

and

front

bracket,

and

remove

the

display

pce

board.

4.

Memory

Preservation

This

unit

does

not

require

memory

preservation

bat-

teries.

A

built-in

memory

power

back-up

system

preser-

ves

contents

of

the

memory

during

power

failures

and

even

when

the

unit

is

unplugged.

The

unit

must

be

plug-

ged

in

and

the

power

switch

turned

on

and

off

once

in

order

to

charge

the

back-up

system.

Note

that

since

this

is

not

a

permanent

memory,

the

power

switch

must

be

turned

on

and

off

a

few

times

each

month

to

keep

the

back-up

system

operable.

The

period

of

time

during

witch

memory

contents

are

preserved

after

power

has

last

been

turned

off

varies

depending

on

climate

and

the

location

and

placement

of

the

unit.

On

the

average,

memory

contents

are

protected

over

a

period

of

3

to

4

weeks

(a

minimum

of

2

weeks)

after

the

last

time

power

has

been

turned

off.

This

period

is

shorter

when

the

unit

is

exposed

to

very

high

humidity

or

used

in

an

area

with

an

extremely

humid

climate.

Remove

the

two

screws

holding

the

switch

of

F501

F601

Speaker

protection

fuse

F902

F904

F903

:

<G/W>

Pri.

=

TES

il

il

<G>

F901

<pjw>

F905

<G>

Second.

-

a7

A16

“n805)i

\

A805)ago6)

Jt

—

(ur

27

G28)

TX-7230

BLOCK

DIAGRAM

—AMPLIFIER

SECTION—

TUNER

o

BASS

TREBLE

VOLUME

Sel}

pal

S2

BALANCE

RS)

LOUDNESS

Q301

EQUALIZER

AMP

~

2301

$303

SELECTOR

PHONOO)

SOURCE

INDICATOR

»

To.Rch

co.

POWER

SPEAKER:

mReC

QO——+~—____}_

pre

t_-

AMP

PROTECTION

TAPE-1

aaa

PB

HE

ADPHONE

p-REC

TAPE-2

tpa

O—

Q9210922

SPEAKER

A

QS23

DY

NAMIC

BASS

€

XPANDER

owt

LEVEL

°

*

SPEAKER

B

—POWER

SUPPLY

SECTION—

To

FLUORESCENT

INDICATOR

TUBE

—DYNAMIC

BASS

EXPANDER—

OUTPUT

D521,

D522

RECTIFIER

FILTER

other

channel

i.

other

channel

In

earlier

super

base

systems,

only

the

frequencies

about

70Hz

were

boosted

by

about

4dB

to

expand

the

playback

frequ-

ency

response

to

enable

playback

of

the

super

low

region.

However,

when

there

was

no

input

signal,

the

above

frequency

response

resulted

in

deterioration

in

the

S/N

ration

in

the

70Hz

region.

This

problem

has

been

overcome

by

the

dynamic

bass

expander

where

the

70Hz

boosted

level

is

varied

according

to

the

input

signal

level.

That

is,

the

frequency

response

remains

flat

when

no

input

signalis

applied,

but

is

boosted

at

the

70Hz

region

to

the

specified

level

when

the

input

signal

exceeds

a

certain

level.

The

left

and

right

channel

input

signals

from

the

INPUT

terminals

are

mixed

by

Q523

and

pass

through

the

level

volume

and

filter

amplifier.

The

signal

is

rectified

by

D551

and

D552,

and

the

resultant

DC

component

control

signal

is

applied

to

the

gate

of

Q525.

When

the

input

signal

is

at

a

adequate

level,

Q525

is

turned

on

and

the

super

base

circuit

of

power

amplifier

is

controlled

by

the

input

signal.

BLOCK

DIAGRAM

—TUNER

SECTION—

NARF

-

23020!

L302

8

CT

+

SR

|

:

LET

H

|

JFeceu23

|

gt.

a

ASENNA

i

j .

x101

@101-x102,

Q102,—Ssx103

hee

L201

:

1p.

TERMINAL

RF

FM

iF

FM

tf

FM

IF

FM

IF

EM

IF

2

DIROIE

a

4

MIXER

IFT

FILTER

AMP

FILTER

AMP

FILTER FILTER

Q20)

STEREO

CECQDER

FM

IF

SYSTEM

(AMP.,MUTING,

METER

&

DET.

}

150|

=

yw

=

=

So

ira

a

z

<

=

re)

z

zr

2

<

=

3

to)

=]

AMP

ANTENNA

TUNED TUNED

CIRCUIT

2

CIRCUIT

CIRCUIT

£103,107

NOISE

DETECTOR

BUFFER

zg

(76KHz)

I

R203

SEPARATION

L203

202

F

GATE

cirRcult

&

IF

AMP.

OFF

AM

LOOP

ANTENNA

Q1s1

AM

RADIO

SYSTEM

aiss

106

GATE

CIRCUIT

Q205

GATE

ciRcult

X1S)

AM

IF

FILTER

GATE

CIRCUIT

TUNED

CIRCUIT

B

g=8

Os:

2

on

zz

3

Q208

MUTING

C)

C

)

Swi

TCH

Q706

AUTO-STOP

SWITCH

Q701

@

l-Our

PRESCALER

Q704,0708

LOW

PASS

FILTER

ey

R-OUT

Q703

STATIC

FREQUENCY

ORIVER

Q702

PLL

SYNTHESIZER

&

CONTROLLER

id,

daeadecedes

i

:

42

STEREO

@)

AUTO

SwiTCH

SWITCH

ons

merce

—

@avze

FaSPeseR”

zj)=z

INOICATOI

a

a

=

2

Stale

SWITCH

pert

&

6

=

2

s

3

lo716

INDICATO!

2

PS

Fe

2

SWITCH

—

—

Fees

2

FA

<

EM

+8

FM

MH

fia

=

2

=

SWITCH

z

AM

PETA

LAT

se

8

0723

soe

7

ae

tures

NADG-23030

CRCUIT

L

fio

:

:

{nicaroal

SWITCH

Q709

GATE

CIRCUIT

GATE

CIRCUIT

+

Q710

5OKHz

.

Inpicaror”

)

SWITCH

TX-7230

EXPLODED

VIEW

PARTS

LIST

REF.

NO.

PART

NO.

DESCRIPTION

REF.

NO.

PART

NO.

DESCRIPTION

REF.

NO.

PART

NO.

DESCRIPTION

Al

27110243

‘Front

bracket

ASOle

28322012A

Selector

knob

ass’y

Ul

18454502D

NARF-2302D,

Tuner

circuit

pc

board

A2

27190198A

Holder,

lamp

ASOIf

28322018A

Knob

ass’y

ass’y

A4

28133132A

Back

plate

A511

838430068

3TTB+6B(BC),

Tapping

screw

U2

18454503D

NADG,

2303D,

Digital

circuit

pc

board

AS

28130225B

Dial

plate

A601

27170198A

Bottom

board

ass’y

A6

27190358A

Holder

A602

27175009A

Leg

U4

18408505

NASW-2305,

Operation

switch

pc

board

AT

27260171B

Shaft

A603

834430068

3TTS+6B(BC),

Tapping

screw

ass’y

A8

27220032A

Slider

A604

834430128

3TTS+12B(BC),

Tapping

screw

US

18448506A

NAAF-2306A,

Dynamic

bass

circuit

A9

27190359A

Holder,

dial

A701

27267402A

Guide,

decoration

pe

board

ass’y

Al0

28198632

Facet

A803

28321928

Knob,

power

<S)

U6

18414507A

NAEQ-2307A,

Equalizer

amplifier

pc

Al2

27115180

Side

bracket

R

28321905B

Knob,

power

(B)

board

ass’y

Al4

27130388

Bracket,

power

transformer

A804

28321886

Knob,

speaker

(S)

U7

18414508A

NASW-2308A,

Source

selector

switch

pc

Al6

27130390

Bracket,

center

28321894

Knob,

speaker

(B)

board

ass’y

Al7

27190011

Holder

A805

28322005A

Knob,

expander

U8

18454509D

NAAF-2309D,

Power

amplifier

and

power

Al9

27160174

Radiator

A806

28322006

Knob,

slide

power

supply

pc

board

ass’y

A21

27260172

Shaft

A807

28322007A

Knob,

loudness

(S)

.

U9

18408510

NATC-2310,

Tone

control

circuit

pc

A22

28320135

Connector

28322020A

Knob,

loudness

(B)

board

ass’y

A24

27120684

Back

panel

A808

28321887A

Knob,

volume

<S)

U10

18448511A

NASW-23114A,

Switch

pc

board

ass’y

A25

27130389B

Bracket

B

28321895

Knob,

volume

(B)

Uil

18408512

NASW-2312,

Speaker

switch

pc

board

A26

A

27300750

—

Strainrelief

A809

28322008

Knob,

balance

(S)

ass‘y

A28

27273030C

Joint

L

28322021A

Knob,

balance

(B)

U12

18408513.

NAHP-2313,

Headphone

terminal

pc

A30

27150202

Shielded

plate

A810

28322009A

Knob,

shift

<S)

board

ass’y

A38

834430068

3TTS+6B(BC),

Tapping

screw

28322022A

Knob,

shift

(B)

U13

18408514

NAVR-2314,

Volume

control

pc

board

A40

:

831130088

3TTW+8B,

Tapping

screw

F501

252076

3.15A-SE-EAK,

Speaker

protecion

ass’y

A41

838440089

4TTB+8C(BC),

Tapping

screw

F601

fuse

u14

18414516

NAPL-2316,

Edge

light

pc

board

ass’y

A42

834430168

3TTS+16B(BC),

Tapping

screw

F902

A,

252074

2A-SE-EAK,

Primary

fuse

A44

834430108

3TTS+10B(BC),

Tapping

screw

F903

A\

252078

5A-SE-EAK,

Secondary

fuse

A46

82142003

2P+3F(BC),

Pan

head

screw

F904

A47

82143006

3P+6FN(BC),

Pan

head

screw

F905

A

252070

1A-SE-EAK,

Secondary

fuse

ASO

880004

Rivert

P904

25060044

Terminal

GND

A301

28184271

Top

cover

(S)

P906

253128

AS

AS-CEE,

Power

supply

cord

28184272

Top

cover

<B>

Q501

222041

STK4843,

Power

amplifier

IC

A302

834430068

3TTS+6B(BC),

Tapping

screw

Q901

222780122

78M12,

Constant

voltage

IC

A501

18452121

Front

panel

ass’y

(S)

T901

232085

NMA-3034,

AM

loop

antenna

A5Ola

27267387

Guide,

speaker

T901la

27190105

Holder,

antenna

A501b

27267386B

Guide,

power

T902

Z\

230870A

NPT-875G,

Power

transformer

A501c

27267398

Guide,

loudness

ASOid

28191293B

Clear

plate

ASOle

28321992A°

Selector

knob

ass’y

ASOILf

28321998A

Knob

ass’y

A501

18472121

Front

panel

ass’y

(B)

ASOla

27267390

Guide,

speaker

A5S01b

27267389B

Guide,

power

AS01c

27267399

Guide,

loudness

A50ld

28191295C

Clear

plate

NOTE:

THE

COMPONENTS

IDENTIFIED

BY

MARK

NOTE:

|

#.

ARE

CRITICAL

FOR

RISK

OF

FIRE

AND

{S):

Only

silver

model

ELECTRIC

SHOCK.

REPLACE

ONLY

WITH

<B):

Only

black

model

PARTS

NUMBER

SPECIFIED.

TX-7230

CIRCUIT

DESCRIPTIONS

1.

Synthesizer

and

controller

operation

Pin

No.

{|

Symbol

Terminal

Description

1

GND

Ground

2

XT

X’tal

Connected

to

the

7.2MHz

crystal

oscillator

for

the

reference

frequency.

FM

band

specification

input

MW

band

specification

input

LW

band

specification

input

Mutual

reset

type,

performs

switching

of

each

band,

FM/MW/LW.

Manual

tuning

mode

specification

input

MANUAL

—-|-__—

8

AUTO

specification

input

Auto

search

tuning

mode

Mutual

reset

type,

performs

auto

search

and

manual

operation

mode

switching

during

UP/DOWN

tuning.

p10

DOWN DOWN

tuning

key

input

Memory

store

command

input

Preset

memory

channel

a

a

a

specification

input

Connect

the

push

key

and

perform

UP/DOWN

tuning.

The

preset

memory

is

set

to

the

write

mode

when

the

key

is

pressed.

Controls

the

write

and

read

out

of

the

internal

16-station

preset

memory

along

with

the

MC]

and

MC2

input.

MC-1

Set the

16-station

preset

memory

to

the

8

FM/8

AM

station

mode

or

Memory

control

input

the

FM/MW/LW

3-band

16-station

random

mode.

The

8

FM/8

AM

MC-2

mode

is

used

in

this

unit.

Osc?

AM

oeallaton

eaaninal

CR

connection

terminal

for

the

oscillator

that

determines

the

scan

speed

during

the

AM

search

mode.

—t

al

2

:

:

CR

connection

terminal

for

the

oscillator

that

determines

the

scan

os!

le

oscillator

terminal

speed

during

the

FM

search

mode.

Output

that

represents

the

SOkHz

FM

band

tuning

step

for

European

o/s

EM

SORHE

output

models.

Goes

to

the

high

level

for

the

50

kHz

setting.

7

CK2

CK

Tuned

frequency

Outputs

the

serial

data

and

timing

clock

to

the

tuned

frequency

display

data

output

driver.

28

MUTE

Muting

signal

output

Goes

to

the

high

level

during

muting

output.

Regin

specification

input

29 E2

30

El

See

table

1.

AM

IF

signal

input

ae

|

31

STOP

3

During

AM

reception,

this

counts

the

IF

signal

and

stops

auto

search.

ae

;

3

STOP

2

Auto

search

stop

When

the

stop

|

input

(pin

33)

is

at

the

high

level

and

this

terminal

2

signal

input

goes

to

the

high

level,

auto

search

is

stopped.

|

=,

: .

. .

*

d

.

33

STOP

1

Scan

speed

slow

input

When

the

high

level

is

input

at

this

terminal,

the

auto

search

speed

is

cut

in

half.

Pin

No.

|

Symbol

Terminal

Description

bs

{

fe

Charge

pump

output

of

the

phase

detector

which

constitutes

the

PLL.

34

DOI

High

level

is

output

when

the

divided

oscillation

frequency

is

high

than

:

the

reference

frequency.

In

the

opposite

case,

low

level

is

output.

{—

—}

Error

output

Floating

occurs

when

the

frequencies

match.

The

output

is

applied

to

the

variable

capacitor

diode

in

the

front

end

through

low

pass

filter

35

DO2

Q704

and

Q705.

The

output

from

both

terminals

is

the

same,

but

only

DOI

is

used.

{

36

TEST

Test

terminal

Test

mode

at

the

high

level.

+}

}..__-_-—

-

7

FM

programmable

“

37

FM

IN

counter

input

Connect

to

the

prescaler

output

(Pin3

of

Q701)

|

38

PSC

ra

a

control

Output

to

the

control

the

division

ratio

of

the

prescaler.

ie

AM

local

oscillator

:

‘ :

39

AM

IN

signal

input

Terminal

for

input

of

AM

broadcast

signal.

40

INH

Inhibit

input

Operates

normally

at

the

high

level.

Inhibit

status

at

the

low

level.

_.

4

1

..

int

idsialigetasat

Operates

normally

at

the

high

level.

At

the

low

level,

the

internal

status

a

a

is

initialized.

ea?

Mog

eee

le

|

‘Pewee

power

terminal;

:

supplies

5V

during

the

normal

operation

and

42

Yee

Power

stply

2.5V

from

the

super

capacitor

(C712)

for

memory

preservation.

be

table

|.

E]

E2

ei

Bane

i

Frequency

Intermediate

Reference

(Pin

30)

(Pin

29)

pa

a

range

frequency

step

frequency

-+—--_—_—___--—_}.

fp

—

FM

87.5

~

108.0

MHz

+10.7

MHz

100

kHz

25

kHz

0

l

foes

ht

ong

SO

U.S.A

AMI

520

~

1

710

kHz

+450

kHz

10kHz

10

kHz

ak

eles

|

eeeseen

|

l

AM2

522

~

1710

kHz

+450

kHz

9kHz

9kHz

|

FM

+10.7MHz

|

SO

kHz

25

kHz

fe

a

ee

]

0

Europe

|

MW

522

~

1611

kHz

+450

kHz

9

kHz

9

kHz

LM

153

~

360

kHz

+450

kHz

1

kHz

_t

FM

76.0

~

90.0

MHz

-

10.7

MHz

100

kHz

0 0

Japan

i.

AM

522

~

1611

kHz

+450

kHz

9

kHz

2.

Auto

Hi-blend

switch

circuit

The

Q103

FM

IF

system

incorporates

IC’s

with

a

built-in

IF

level

detector

with

a

13

pin

output.

If

an

input

above

38dB

enters

the

antenna,

Q205

is

turned

on,

and

Q721

is

turned

on,

the

Q722

and

Q202

are

turned

off

and

the

high

blend

function

is

turned

off.

—9—

TX-7230

3.

Auto

search

tuning

circuit

Q103

FM

IF

SYSTEM

TO

STEREO

DECODER

D811

Ww

WwW

0702

CONTROLLER

Q806

NOISE

DETECTOR

From

AM

IC

To

:

Signal

indicator

circuit

Maximum

frequency

Station

B

Station

A

Start

Minimum

frequenc

=

a

(fig.

4)

4.

FM/AM

switch

circuit

+B

Q702

Q155

Q709

(ON

The

FM/AM

selector

circuit

is

shown

in

the

diagram.

fig.5.

Pins

4

and

5

of

Q702

are

of

the

mutual

reset

type.

For

FM,

pin

4

is

high

and

pin

5

is

low;

for

AM,

pin

4

is

low and

pin

5

is

high.

Because

pin

5

is

high

and

pin

4

is

low

during

AM

reception,

Q709

is

off,

the

AM,

kHz

segments

of

the

fluores-

cent

display

are

turned

on.

Also,

since

Q708

goes

to

on

and

Q714

is

turned

off,

and

the

FM

indicators

are

turned

off.

At

the

same

time,

Q155

is

turned

off

and

Q154

turned

on,

so

+B

is

supplied

to

the

power

source

terminal

of

the

radio

Q154

To

AM/kHz

segment

To

FM/MHz

segment

During

FM

reception,

this

is

operated

by

the

IF

level

detec-

tion

and

zero

point

detection

circuits

included

in

the

FM

IF

system

IC

of

Q103

and

by

the

noise

component

detection

circuit

of

Q806.

When

a

station

is

tuned,

the

output

of

all

outputs

go

to

the

low

level

so

Q843

goes

from

on

to

off,

causing

pins

32

and

33

of

the

controller

IC

to

go

to

the

high

level

to

complete

auto

search

tuning.

During

AM

reception,

this

is

operated

by

the

IF

level

detec-

tion

included

in

the

AM

radio

system

IC

of

Q151.

When

a

station

is

turned,

Q152

goes

from

off

to

on

and

Q706

goes

to

off,

causing

pins

32

and

33

of

the

controller

IC

to

go

to

the

high

level

to

complete

auto

search

tuning.

@

Manual

Tuning

When

the

UP

or

DOWN

key

is

pressed,

the

frequency

goes

up

or

down

by

one

step.

When

either

key

is

held

down,

the

frequency

rapidly

increases

or

decreases

(scans)

and

stops

when

the

key

is

released.

When

either

end

of

the

turning

range

is

reached,

key

input

will

no

longer

be

received

and

the

frequency

will

stop

at

the

highest

or

lowest

frequency.

e@

Auto

Tuning

When

the

UP

or

DOWN

key

is

pressed,

scanning

begins

in

the

up

or

down

direction,

stopping

where

there

is

a

radio

station.

Since

auto

scan

is

operated

by

a

trian-

gular

wave,

scanning

is

begun

in

the

opposite

direction

the

instant

either

end

of

the

tuning

range

is

roached.

Also,

if

the

UP

or

DOWN

key

is

pressed

when

the

tuned

frequency

is

not

at

either

end

of

the

range,

up

or

down

scanning

will

begin.

Pin

16

of

Q201

VCO

stop

terminal

of

stereo

decoder

Pin

2

of

Q103

FM

IF

Amp,

stop

inpu

Muting

circuit

———

-

D119

Q108

Pins

8

&

14

AM

B+

Terminals

(

):

FM

reception

from

A.

G.

C

detector

circuit

(fig.

5}

system

pins

8

&

14

of

QIS].

Pin

16

of

Q201

goes

to

the

high

level,

the

VCO

oscillator

stops,

and

pin

2

of

Q103

gose

to

the

high

level

so

the

FM

IF

amp

is

also

switched

off.

Also,

during

AM

reception,

Q108

is

turned

on

so

the

muting

circuit

is

off.

During

FM

reception,

all

of

the

switching

transistors

mentioned

above

perform

the

opposite

operations

to

switch

to

the

FM

mode.

Figures

in

parenthese

indicate

transistor

Operation

during

FM

reception.

—10—