Pioneer Tx-9800 User manual

etvice

c

/Vlanual

AM/FM

STEREO

TUNER

TX=-93800

Y

PIONEER’

i

a

MODEL

TX-9800

COMES

IN

FOUR

VERSIONS

DISTINGUISHED

AS

FOLLOWS:

Voltage

Remarks

120V

U.S.A.

model

110V,

120V,

220V

and

240V

(Switchabie)

General

export

mode!

110V,

120V,

220V

and

240V

(Switchable)

U.S.

Military

model

220V

and

240V

(Switchable)

Europe

or

Oceania

mode!

©

Although

the

basic

features

of

KU,

S,

S/G

and

HG

types

are

the

same.

The

major

difference

is

in

appearance,

KU,

and

S/G

types

being

fitted

with

wooden

case,

while

S

and

HG

types

employ

metal

cover.

@

This

service

manual

is

applicable

to

the

KU

type.

When

repairing

the

S

and

S/G

types,

please

see

the

additional

in

this

service

manual

(p37

—

p43).

When

repairing

the

HG

type,

please

see

the

additional

service

manual

(ART-347-0).

CONTENTS

1.

SPECIFICATIONS

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

000002

eee

3

Additional

Service

Manual

2.

FRONT

PANEL

FACILITIES..............

4

1.

SPECIFICATIONS

...........

2.000880

3.

BLOCK

DIAGRAM............0.

0000

enue

5

2.

CONTRAST

OF

MISCELLANEOUS

PARTS

....

4.

CIRCUIT

DESCRIPTIONS

3.

SUPPLEMENTS

FOR

S

AND

S/G

TYPES

4.1

Signal

Circuit...

2.2.2.0...

ee

eee

5

3.1.

Schematic

Diagram

.......

602?

AD

SWAPO

CHOU

uns

ea

won

amstettn

eee

7

3.2

Tuner

Assembly

(GWE-116)

..

-

+--+

>>

4.3.

Control

Circuit...

0.0.0.0...

00.000

ae

9

3.3

LED

Assembly

1

(GWX-252).

.

-

sss

44

AMTuner......

0.2.20

eee

ee

11

3.4

LED

Assembly

2

(GWX-253).

. -

+--+

+++:

DISASSEMBLY

sc3cuacde

venues

vous

Mawes

12

3.5

Switch

Assembly

(AWX-113)

. -

+--+

=

6.

DIALCORDSTRINGING

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

13

3.6

Power

Supply

Assembly

(AWR-190)

7.

ADJUSTMENTS

7.10

AMTuner

....

2.

eee

14

FZ”

EM

Tune

on

eae

eee

oh

ee

a

aes

ke

15

8.

PARTS

LOCATION

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

00000

18

9.

EXPLODED

VIEW

................000.

20

10.

SCHEMATIC

DIAGRAM

P.C.

BOARD

PATTERNS

AND

PARTS

LIST

10.1.

Miscellanea...

...

ee

23

10.2

Schematic

Diagram

..............0.0.

25

10.3.

P.C.

Board

Connection

Diagram.........

28

10.4

Parts

List

of

P.C.

Board

Assemblies.......

31

TA

PACKING

2...

ods

ctotnd

selene

a

halw

aes

34

1.

SPECIFICATIONS

Semiconductors

FM

Section

Usable

Sensitivity

.......

50dB

Quieting

Sensitivity

.

Signal-to-Noise

Ratio

at

85dBf

...........

Distortion

at

85dBf......

Capture

Ratio...........

Alternate

Channel

Selectivity

Stereo

Separation

........

MONO:

8.8dBf

(1.5uV)

MONO:

=

13.2dBf

(2.5uV)

STEREO:

36.1dBf

(35uV)

MONO:

=

83dB

STEREO:

80dB

MONO:

100Hz

0.05%

1kHz

0.04%

10kHz

0.06%

STEREO:

100Hz

0.1%

1kHz

0.07%

10kHz

0.2%

WIDE

NARROW

eteNaege

ye

0.8dB

2.0dB

puede

ane

et

30dB

85dB

TkHz:

55dB

20Hz

to

10kHz:

40dB

Frequency

Response

.....

Spurious

Response

Ratio

.

Image

Response

Ratio

....

IF

Response

Ratio.......

AM

Suppression

Ratio

....

Subcarrier

Product

Ratio

..

Muting

Threshold

.......

De-Emphasis

Switch

(Switchable).........

Antenna

Input

.........

AM

Section

Sensitivity

IHF,

ferrite

antenna.

...

IHF,

external

antenna

.

Selectivity

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

Signal-to-Noise

Ratio...

..

Image

Response

Ratio

....

IF

Response

Ratio.......

Antenna

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

Audio

Section

Output

(Level/Impedance)

FM

(100%

MOD.)

.....

20Hz

to

10kHz

£0.2dB

20Hz

to

15kHz

+92

dB

110dB

120dB

110dB

65dB

70dB

19.2dBf(5uV)

25us

~

75ys

300ohms

balanced

75ohms

unbalanced

300uV/m

15yuV

WIDE;

20dB

NARROW;

50dB

55dB

70dB

65dB

Ferrite

Loopstick

Antenna

FIXED:

650mV/4.2kQ

VARIABLE:

S0mV

to

1.3V/3.6kQ

AM

(30%

MOD.)......

FIXED:

200mV/4.2kQ

~

VARIABLE:

15mV

to

400mV/3.6kQ

Multipath

V

(Vertical).........

300mV/10kQ

(AM

1kHz

30%

MOD)

H

(Horizontal)

.......

400mV/7kQ.

(FM

1kHz

100%

MOD)

Miscellaneous

Power

Requirements

.....

120V

60Hz

only.

Power

Consumption

.....

28W

Dimensions

...........

453(W)

x

155(H)

x390(D)

mm

17-11/16

x

6-1/8

x

15-3/8in

Weight)

so.

..005.

25003

29

Without

Package:

9.3kg

(20Ib

802)

With

Package:

10.7kg

(23lb

90z)

Furnished

Parts

FM

T-typeantenna................0002

cee

eee

1

Connection

Cord

with

Plugs..................

1

Operating

Instructions

................0...000-

1

NOTE:

Specifications

and

the

design

subject

to

possible

modifica-

tion

without

notice

due

to

improvements.

POWER

SWITCH

Set

to

ON

position

to

turn

on

power.

Pilot

lamp

will

light

up.

SIGNAL

METER

This

meter

indicates

the

antenna

input

level

of

the

AM

and

FM

broadcasting

waves.

The

higher

the

input

level,

the

more

the

meter

deflects

toward

right.

When

selecting

the

desired

station,

find

the

position

of

the

tuning

knob

which

effects

the

maximum

deflection

of

the

meter

pointer.

When

selecting

an

FM

station,

also

observe

the

tuning

meter

to

determine

the

optimum

tuning

point.

TUNING

METER

This

meter

indicates

the

optimum

tuning

point

irrespec-

tive

of

the

field

strength

when

selecting

an

FM

station.

With

no

signal,

the

pointer

remains

at

the

center;

as

a

signal

is

tuned

in,

it

deflects

to

the

right

or

left;

when

the

signal

is

tuned

in

accurately,

the

pointer

will

correctly

move

to

the

center

of

the

scale.

If

the

tuning

knob

is

ad-

justed

further,

the

pointer

deflects

to

the

right

or

left;

as

the

signal

moves

off

completely,

the

pointer

returns

to

the

center

position

again.

MEMORY

MARKERS

Convenient

for

designating

most

often

tuned

in

stations.

Slide

markers

with

fingertip

to

desired

positions.

2.

FRONT

PANEL

FACILITIES

FM/AM

INDICATORS

These

indicators

light

up

during

an

FM

or

AM

reception,

respectively.

FM-LOCKED

INDICATOR

With

the

function

switch

set

to

FM

and

the

FM

muting/

mode

switch

set

to

ON,

this

indicator

lights

up

when

you

take

your

hand

off

the

tuning

knob

at

the

optimum

tuning

point.

This

light

indicates

that

the

quartz

locking

circuit

has

been

activated

by

the

built-in

touch

sensor

de-

tector

circuit

and

the

frequency

of

the

circuit

is

locked

to

the

frequency

of

the

station.

FM-TUNE

INDICATOR

This

indicator

lights

up

when

the

optimum

tuning

point

is

obtained.

FM-STEREO

INDICATOR:

This

indicator

lights

up

when

‘the

tuner

is

receiving

a

stereo

program

if

the

FM

MUTING/MODE

switch

is

set

to

AUTO.

Pilot

lamp

isle

=|

OUTPUT

LEVEL

KNOB—

This

knob

is

used

to

adjust

the

output

level

of

the

variable

output

jacks.

When

it is

rotated

in

the

direction

of

MAX,

the

output

level

is

increased.

TUNING

KNOB

This

knob

is

used

for

selecting

stations.

When

selecting

an

AM

station,

observe

the

signal

meter,

and

when

selecting

an

FM

station,

observe

both

the

signal

meter

and

the

tuning

meter.

FUNCTION

SWITCH

This

switch

is

used

to

select

the

type

of

broadcasting

waves.

FM....

Forreception

of

FM

broadcasting

AM....

For

reception

of

AM

broadcasting

=i

Tx-9SsoO

MPX

NOISE

FILTER

SWITCH

If

a

comparatively

high

frequency

noise

is

noticed

during

reception

of

a

stereo

program,

this

switch

is

set

to

ON.

Stereo

separation

will

thereby

somewhat

deteriorate.

This

switch

should

normally

be

kept

OFF.

FM

MUTING/MODE

SWITCH

When

this

switch

is

set

to

ON,

unpleasant

interstation

noise

is

eliminated,

which

makes

selection

of

stations

easier.

However,

if

the

muting

switch

is

set

to

ON

in

areas

where

the

field

strength

is

extremely

weak,

the

station

be-

ing

received

may

also

disappear.

In

such

areas,

therefore,

the

muting

switch

should

be

turned

OFF.

When

this

switch

is

set

to

OFF,

monaural

reception

will

be

obtained

even

though

the

station

is

broadcasting

a

stereo

program.

FM-AM

IF

BAND

SWITCH

FM

and

AM

IF

(intermediate

frequency)

passband

can

be

set

to

for

wide

or

narrow.

This

switch

is

used

to

select

between

NARROW

(narrow

band)

and

WIDE

(wide

band).

In

this

way,

it

is

possible

to

change

over

the

pass

bandwidth

of

the

intermediate

frequency

signals.

NARROW

...

When

tuning

in

the

desired

station,

and

if

adjacent

station

interference

is

a

problem

at

the

WIDE

setting,

set

switch

to

this

position.

WIDE......

Set

the

switch

to

this

position

after

the

desired

station

was

received

without

ad-

jacent

station

interference.

3.

BLOCK

DIAGRAM

[”

FM

FRONT

ENO

aae

ANTENNA

SINGLE

INGLE

DOUBLE

eae

TUNE

750

soon!

fea

|

Leo

pelea

eae

fi

/t

BUFFER

AMP

SAMPLING

|

[BUFFER

HOL

D

AMP

Xtal

PULSE

osc

[Jf

*

“64

Flrormine

APC

AM

apitenna!

[SINGLE

©

TUNE

°

(2)

{

SINGLE

|

TUNE

ee

a

AM

TUNER

—

4.

CIRCUIT

DESCRIPTIONS

4.1

SIGNAL

CIRCUIT

FM

Front-end

The

FM

front-end

of

this

set

uses

a

precision

frequency-linear

type

5-ganged

tuning

capacitor.

The

circuit

is

shown

in

Fig.

4-1.

The

antenna

input

is

made

an

unbalanced

(752)

by

an

M-

coupled

single-tuned

circuit.

The

RF

stage

uses

two

dual-gate

MOS

FETs

(Q,,

Q,)

having

superior

high-

frequency

characteristics.

The

interstage

tuning

circuits

are

C-coupled

double-tuned

for

improved

reception.

The

phase

characteristic,

spurious

interference

ratio,

and

IF

interference

ratio

are

especially

good.

A

dual-gate

MOS

FET

(Q;)

is

also

used

at

the

mixer

stage.

The

received

signal

is

applied

to

gate

1

and

the

local

oscillator

signal

is

input

at

gate

2.

The

converted

output

(10.7MHz)

is

taken

from

the

drain

and

applied

to

the

IF

amplifier

thru

an

IFT.

The

local

oscillator

(Q,)

is

modified

Clapp

circuit.

Its

output

is

fed

to

the

mixer.

D,

of

the

local

oscillator

is

a

vari-cap

diode

that

forms

part

of

the

tuning

capacitance.

A

vari-cap

diode

is

an

element

whose

capacitance

can

be

controlled

by

means

of

the

impressed

voltage,

and

is

designed

to

control

the

voltage

relative

to

local

oscillator

frequency

deviation

to

within

+100kHz.

This

control

voltage

is

obtained

from

an

APC

LOCAL

osc

(vco)

FM

IF

AMP

poe

roe

ir

DIODE

H

SWITCH

ii

TUNING

KNOB

\\

Z

J

ZA

Q

Touch

|

|RecTIFIER

|

[SCHMITT

SENSOR

|

}

\"§

SENSOR

GAIN

BUFFER

AMP

------------

------------5

ie;

=

(Automatic

Phase

Control)

circuit.

(See

the de-

scription

of

the

APC

circuit

on

page

7.)

IF

Amplifier

This

tuner

employs

a

dual

IF

amplifier

consist-

ing

of

a

wide

band

IF

amplifier

designed

for

high

separation,

low

distortion

reproduction,

and

a

narrow

band

IF

amplifier

used

for

rejection

of

interference

signals

(Fig.

4-2).

The

wide

band

IF

amplifier

has

been

designed

with

the

minimum

number

of

frequency

selective

elements,

with

emphasis

being

placed

on

linear

phase

characteristics.

The

narrow

band

IF

amplifier

on

the

other

band,

has

been

designed

with

em-

phasis

on

selectivity.

When

the

selector

switch

is

in

the

wide

position,

the

signal

path

is

FM

front-

end

>

Q,

>

F,

>

Q,>

T,

>

Ds,

Ds

>

PA8001-A,

while

in

the

narrow

position

it

is

FM

front-end

>

Q,

>

F,

>

Q,

>

T,

>

D,

>

narrow

IF

amp.

D,>

PA38001-A.

The

changeover

between

wide

and

narrow

is

performed

of

diode

switches

(D,

to

D,).

When

the

selector

switch

is

in

the

wide

position,

D,

and

D,

are

biased

in

the

forward

direction

and

D,

and

D,

are

biased

in

the

reverse

direction,

thus

bypassing

the

narrow

IF

amplifier.

When

the

selector

switch

is

in

the

narrow

position,

D,

and

D,-are

forward

biased

and

D,

and

Dg,

are

reverse

biased.

INDICATOR

@

©

@@

DIODE

q

é

lie

i

a

Soe

eee

ee

Ae

eet

=

(X)

®

(PA3OOI-

A)

FUNCTION

ANTENNA

{

——

oF!

75Q

1

Sat

FM

STEREO

DEMODULATOR

(PAIOOI

-

MPX

A)

ears

‘@

©

CERAMIC

FILTER

IF

AMP

MPX

NOISE

ta

MPX

NOISE

FILTER

rowan

EE

SEPARA-

aa

—

i

TION

fle

ricter

|JcontroiL

ta

@

®

6

fa

so,

IF

BAND

APC

+8

Function|

S

VOLTAGE

oo

7

|

REGULATOR

Oo

recririen|

CONSTANT

VOLTAGE

&)

DE-

MEHASIS

ouTPuT

Oi

FIXED

es

OUTPUT

LEVEL

&

aa

oa

sanikate

Aon

Dx5

MULTI

PATH

avs

POWER

SUPPLY

Ez!

FUNCTION

INDICATOR

BUFFER

AMP

ee

osc

to

APC

CIRCUIT

Fig.

4-1

FM

front-end

Q7

Fig.

4-2

FM

IF

amplifier

:

“ae

van:

CAP

towe

R

E

—=to

IF

AMP

—

AGC

from

f

CIRCUIT

NARROW

O

WIDE

\F

BAND

+B

Multiplex

Decoder

An

IC

(PA1001-A)

developed

by

Pioneer

is

used

in

the

stereo

demodulation

circuit.

PA1001-A

contains

a

PLL

system

VCO

(Voltage

Controlled

Oscillator),

NFB

demodulator,

automatic

pilot

conceller,

and

stereo/mono

automatic

switch.

The

NFB

demodulator

and

automatic

pilot

can-

celler

are

special

features

of

this

IC.

The

NFB

demodulator

suppresses

distortion

caused

by

the

non-linearity

of

the

demodulation

circuit.

The

automatic

pilot

canceller

cancels

the

pilot

signal

(19kHz)

in

the

stereo

demodulation

signal.

This

circuit

cancels

the

pilot

signal

(19kHz)

in

the

stereo

demodulated

signal

by

applying

the

19kHz

from

the

VCO

synchronized

with

the

pilot

signal

(19kHz)

in

the

composite

signal

to

the

stereo

demodulated

signal

thru

an

AGC

amp.

Moreover,

since

the

cancel

signal

level

tracks

the

input

pilot

signal

level

by

means

of

the

AGC

amp.,

the

re-

jection

ratio

remains

the

same

even

with

changes

in

input

pilot

signal

level.

Output

Amplifier

An

AF

MUTE

IC

(PA1002-A)

is

employed

in

the

final

stage

of

the

tuner.

This

IC

contains

two

AF

amplifiers

for

L

and

R

channels,

together

with

a

muting

gate

circuit.

These

AF

amplifiers

employ

time

constant

NFB

to

provide

de-emphasis

charac-

teristics.

The

muting

gate

circuit

is

electrically

connected

to

the

signal

circuit

when

a

DC

voltage

is

applied

to

no.8

of

the

PA1002-A

(Refer

to

muting

control

in

page

10).

4.2

APC

CIRCUIT

The

APC

circuit

stablizes

the

receiving

state

by

suppressing

changes

in

the

FM

front-end

local

oscillator

frequency.

This

circuit

is

a

PLL

circuit

that

controls

the

frequency

of

the

local

oscillator

(VCO;

Voltage

Controlled

Oscillator)

by

comparing

the

phase

of

a

reference

frequency

produced

by

a

crystal

oscillator

and

the

phase

of

the

local

oscillator

frequency,

and

then

using

the

DC

voltage

corre-

sponding

to

their

phase

difference

to

control

the

local

oscillator.

The

capture

range

(range

over

M5S003P

ft

XI/I6

MS3273P

M53293P

6.4MHz

Ar

{Ot

100k

Hz

TX-9800

which

circuit

is

locked)

of

this

APC

is

approxi-

mately

+12kHz,

and

its

lock

range

(range

which

can

be

controlled

by

APC)

is

+75kHz.

Fig.

4-3

is

the

block

diagram

of

this

circuit.

to

IF

AMP

LOCAL

OSCILLATION

SIGNAL

VOLTAGE

SAMPLING

CIRCUIT

SAMPLING

PULSE

GENERATOR

Fig.

4-3

Block

diagram

of

APC

circuit

HOLD

Sampling

Pulse

Generator

This

circuit

uses

3

digital

ICs

and

one

crystal

(Fig.

4-4).

The

crystal

and

two

NAND

gates

on

M5S008P

from

an

oscillator

circuit

that

oscillates

at

the

reference

frequency

(6.4MHz).

This

reference

frequency

is

converted

to

a

100kHz

square

wave

by

dividing

it

by

four with

M53273P

and

then

dividing

it

by

sixteen

with

M53298P.

This

100kHz

square

wave

is

applied

to

two

NAND

gates

on

M5S0038P

and

shaped

to

a

100kHz

sampling

pulse

(Fig.

4-5).

This

sampling

pulse

is

then

applied

to

the

sampling

hold

circuit.

|

©)

lOO

kHz

O°

to

SAMPLING

HOLD

CIRCUIT

Fig.

4-5

Sampling

pulse

generator

Sampling

Hold

Circuit

The

sampling

hold

circuit

compares

the

phases

of

the

local

oscillation

frequency

and

sampling

pulse,

and

generates

a

voltage

corresponding

to

their

phase

difference

(Fig.

4-6).

When

the

sampl-

ing

pulse

is

applied

to

the

base

of

Q;,

Q;

is

turned

on,

and

current

flows

thru

Q,.

When

the

pulse

is

removed,

Q,

is

turned

off,

and

a

flyback

pulse

is

generated

at

the

base

of

Q,

at

this

instant

by

the

inductance

component

of

the

circuit.

C,

is

charged

by

this

flyback

pulse

and

Q,

is

then

turned

off.

When

the

pulse

is

applied,

the

charge

across

C,

is

discharged

thru

Q,;

and

C;

is

recharged

by

the

flyback

pulse

generated

at

the

base

of

Q;

at

this

time.

The

voltage

waveforms

of

each

part

are

shown

in

Fig.

4-7.

This

becomes

as

shown

in

Fig.

4-8

when

the

local

oscillation

fre-

quency

is

applied

to

the

base

of

Q,.

Fig.

4-8a

is

the

waveform

when

the

sampling

pulse

and

local

oscillation

frequency

are

in

phase,

and

Fig.

4-8b

is

the

composite

waveform

when

there

is

a

phase

difference.

Therefore,

a

voltage

corresponding

to

the

phase

difference

between

the

sampling

pulse

and

local

oscillation

frequency

is

hold.

The

C,

hold

voltage

waveform

is

shown

in

Fig.

4-9.

+B

-~—_+>—

2

LOCAL

OSCILLATION

+

Pao’

to

LPF,

OC

AMP

™

SAMPLING

PULSE

ee

Fig.

4-6

Sampling

hold

circuit

SAMPLING

PULSE

i

ens

cee

FLYBACK

PULSE

FET

SWITCH

CONTROL

to

APC

BEAT

DETECTOR

Q2

BASE

!

'

Q2

EMITTER

|

(C5

HOLD

VOLTAGE)

DISCHARGED

BY

CHARGED

BY

SAMPLING

PULSE

FLYBACK

PULSE

Fig.

4-7

Voltage

waveforms

a

Local

osc.

signal

Flyback

pulse

Q2

base

biase

b

Local

osc.

signai

Flyback

pulse

~<—

Level

according

to

phase

of

local

osc.

signal

<—

Q)

base

biase

Y

Fig.

4-8

Q2

base

waveforms

a

When

tuned

at

center

of

hold

range

\

Standerd

voltage

{Cs

hold

voltage)

b

When

focal

osc.

has

attempted

to

move

to

a

lower

frequency

Standerd

SSS

ee

eer

tev

voltage

“Cs

hold

r

voltage

c¢

When

local

osc.

has

attempted

to

move

to

a

higher

frequency

“

Cs

hold

voltage

~~

Standerd

voltage

d

When

deviated

from

APC

lock

Cs

hold

o

voltage

Fig.

4-9

Cs

hold

voltage

waveforms

4.2

CONTROL

CIRCUIT

NOTE:

The

control

circuit

is

operated

digitally.

Consequently,

voltage

changes

are

represented

by

“‘H”’

(high

level

volt-

age)

and

“‘L”’

(low

level

voltage)

in

the

description.

APC

Operation

Control

The

FET

switch

(Q;)

in

the

APC

circuit

is

turned

off

when

the

tuning

knob

is

touched.

During

this

time,

a

reference

voltage

(+8V)

is

applied

to

the

variable

capacitance

diode

in

the

FM

front-end

local

oscillator

to

permit

station

tuning

operations

with

the

APC

turned

off.

When

an

input

signal

whose

antenna

input

level

is

at

least

20dBf

(5.5uV)

is

tuned,

the

TUNE

indicator

LED

is

turned

on.

And

when

the

tuning

knob

is

then

released,

the

FET

switch

(Q;)

is

turned

on,

thereby

completing

the

APC

circuit

loop

to

“lock”

the

local

oscillator

frequency.

The

TUNE

indicator

LED

subsequently

turns

off,

and

the

LOCKED

indicator

LED

turns

on

instead.

These

operations

are

all

controlled

by

the

touch

sensor,

APC

beat

detector,

and

the

output

from

no.12

of

the

IF

system

IC

(PA38001-A).

(See

Fig.

4-10).

When

the

tuning

knob

is

touched

by

hand,

noise

voltage

induced

by

the

human

body

is

detected

and

amplified

by

the

touch

sensor.

The

sensor

output

is

then

rectified

and

employed

as

the

Schmitt

A

control

voltage.

When

an

APC

beat

signal

of

at

least

7kHz

appears

at

the

output

of

the

sampling

hold

circuit,

it

is

detected,

and

then

amplified

by

the

APC

beat

detector.

(APC

beat

signals

are

generated

at

the

sampling

hold

circuit

output

if

the

FM

front-end

local

oscillator

fails

APC-—PLL

Tx-9800

to

remain

at

an

integer

multiple

of

100kHz.

The

frequency

of

this

beat

signal

lies

within

the

DC

~

50kHz

range,

and

is

determined

by

the

phase

dif-

ference

between

the

sampling

pulse

and

the

oscil-

lator

frequency).

The

output

of

the

APC

beat

detector

is

rectified,

and

employed

as

the

Schmitt

B

control

voltage.

When

a

station

is

tuned

away

by

more

than

+65kHz,

or

if

the

antenna

input

level

is

below

20dBf,

a

DC

voltage

appears

at

no.12

of

the

IF

system

IC

(PA3001-A),

this

also

being

used

to

control

Schmitt

B.

Consequently,

when

the

antenna

input

level

of

the

tuned

signal

exceeds

20dBf,

the

collector

volt-

age

of

Q;,

in

Schmitt

A

will

be

set

to

“‘L’’,

and

the

collector

voltage

of

Q33

set

to

‘‘H’’.

And

with

the

collector

voltage

of

Q3,

in

Schmitt

B

at

““H”’,

the

collector

voltage

of

Q3,

is

also

set

to

“H”

(by

the

Q3,.

collector

voltage).

The

base

voltage

of

Q3;

is

thereby

increased,

resulting

in

this

transistor

being

turned

on

to

light

up

the

TUNE

indicator.

Since

Q34

remains

off

because

of

a

low

base

voltage,

the

LOCKED

indicator

does

not

light

up

at

this

time.

And

since

Q3,

has

already

been

turned

on

by

the

collector

voltage

of

Q37,

the

gate

voltage

of

the

APC

circuit

FET

switch

(Q;)

will

be

low,

which

means

this

switch

will

also

remain

off.

When

the

tuning

knob

is

then

released,

the

col-

lector

voltages

of

Schmitt

A

Q3,

and

Qs3;,

and

Schmitt

B

Q3,

will

all

be

inverted,

resulting

in

Q3;

(TUNE

indicator

LED)

being

turned

off,

and

Q3,4

(LOCKED

indicator

LED)

being

turned

on.

Qa.

is

also

turned

off

to

turn

the

FET

switch

(Q;)

on.

BUFFER

vco

AMP

{LOCAL

OSC)

SAMPLING

HOLD

CIRCUIT

FET

?,.

SAMPLING

PULSE

GENERATOR

TOUCH

SENSOR

SCHMITT

A

TUNING

KNOB

Q30

Q31

POWER

TRANSFORMER

ac

Line

3

TIMING

TRIGGER

CIRCUIT

APC

BEAT

DETECTOR

FUNCTION

Fig.

4-10

APC

operation

control

circuit

F

[

!

Timing

Trigger

Circuit

This

circuit

is

designed

to

delay

the

lighting

up

of

the

indicator

LEDs

(TUNE,

LOCKED,

STE-

REO)

when

the

power

is

switched

on,

and

to

turn

them

off

immediately

when

the

power

is

switched

off

again.

(See

Fig.

4-10).

When

the

power

is

switched

on,

Q2.

is

turned

off

immediately

by

a

negative

voltage

applied

via

D,.-

The

base

voltage

of

Q,,

is

thereby

increased

gradually,

the

increase

being

controlled

by

the

Rii3/C1;3

time

constant.

Once

the

voltage

reaches

+1.2V

(approx.),

Q,7

and

Q.,

are

both

turned

on,

thereby

tuming

on

all

relevant

indicator

LEDs.

When

the

power

is

switched

off

again,

the

negative

voltage

applied

via

D,,

is

cut

immediately,

resulting

in

Q.,

being

turned

on.

C,,3;

therefore

discharges

directly

via

Q..

to

turn

Q,7

and

Q2,

off.

All

indicator

LEDs

will

consequently

turn

off

immediately.

This

same

result

is

also

achieved

when

the

FUNCTION

selector

is

in

the

AM

posi-

tion.

This

is

due

to

the

fact

that

the

base

of

Q,,

is

connected

to

ground

by

the

FUNCTION

selector,

thereby

turning

Q,7

and

Q»,

off.

Re-lock

Trigger

Circuit

When

the

power

is

switched

on,

this

re-lock

trigger

circuit

activates

a

sweep

of

the

local

oscil-

lator

frequency,

covering

a

range

of

up

to

100kHz

both

sides

of

the

frequency

indicated

by

the

dial

pointer

at

the

time.

If

a

signal

of

antenna

input

level

in

excess

of

20dBf

is

detected

in

this

range,

the

frequency

is

automatically

re-locked

by

the

APC

circuit.

(See

Fig.

4-11).

In

this

case,

when

the

power

is

switched

on

Q.3

is

turned

off

immediately

by

the

negative

volt-

age

applied

via

D,,,

resulting

in

the

voltage

changes

at

different

places

describing

different

curves

as

shown

in

Fig.

4-12.

The

voltage

applied

to

the

variable

capacitance

diode

in

the

local

oscillator

is

represented

by

curve

(e),

thereby

causing

the

local

oscillator

frequency

to

change,

or

‘“‘sweep”

within

a

limited

range.

If

an

input

signal

whose

antenna

input

level

exceeds

20dBf

is

detected

during

this

sweep,

the

APC

circuit

FET

switch

is

turned

on,

Fig.

4-11

Re-lock

trigger

circuit

10

resulting

in

the

frequency

of

that

input

signal

being

locked

by

the

APC

circuit.

Muting

Control

Circuits

This

tuner

features

3

major

muting

actions.

(1)

Inter-station

muting

in

the

FM

band

and

mut-

ing

of

weak

FM

stations.

(2)

Muting

of

switching

noises

when

FUNCTION

selector

and

IF

BAND

switch

are

operated.

(3)

Muting

when

POWER

switch

is

turned

on

and

off.

All

muting

action

is

controlled

by

the

muting

gate

included

in

the

AF

MUTE

IC

(PA1002-A).

(See

Fig.

4-13).

(1)

Inter-station

Muting

in

FM

Band

When

any

FM

input

signal

whose

antenna

input

level

is

below

20dBf

(5.5uV)

is

received

(which

also

covers

the

case

when

no

input

signal

is

re-

ceived),

a

DC

voltage

appears

at

no.12

of

the

IF

system

IC

(PA3001-A).

If

the

MUTING

switch

has

been

turned

on,

this

DC

voltage

is

applied

to

no.8

of

the

AF

MUTE

IC

(PA1002-A)

to

activate

the

muting

circuit.

(2)

Muting

of

Switching

Noises

(FUNCTION

Selector

and

IF

BAND

Switch)

When

either

the

FUNCTION

selector

or

the

IF

BAND

switch

is

switched

to

another

position,

the

Q,»

base

potential

is

dropped

momentarily,

result-

ing

in

Q.5

being

turned

on

during

the

same

brief

moment.

During

this

interval,

C,,,

is

charged

up,

the

charge

then

being

applied

to

no.8

of

PA1002-A.

The

muting

time

is

thus

determined

by

the

C,,4/Ri15

time

constant.

(3)

Power

Switch

Muting

The

muting

trigger

employed

when

the

POWER

7

res

ON

©

2

oe

@)

Cee

ee

ah

1

5

es

ee

ON

I

©

)

canter

oo

<

Fig.

4-12

Voltage

waveforms

switch

is

turned

on

and

off

is

formed

by

Q,;

and

Q.;.

When

the

POWER

switch

is

turned

on,

Q,;

is

tured

off

by

the

negative

voltage

applied

via

D,..

The

consequent

voltage

changes

at

points

(a)

and

(b)

are

shown

in

Fig.

4-14.

The

point

(b)

voltage

is

applied

to

no.8

of

PA1002-A.

When

the

POWER

switch

is

turned

off,

Q.3

is

turned

on

due

to

the

immediate

cut

off

of

the

negative

voltage

applied

via

D,,.

Q.,;5

is

then

turned

off

as

a

result

of

the

voltage

at

point

(a)

dropping

to

OV,

thereby

generating

a

muting

trigger

action

at

point

(b).

4.4

AMTUNER

The

AM

tuner

stage

is

equipped

with

a

3-ganged

tuning

capacitor

and

an

IC

(HA1197).

The

IF

amplifier

stage

includes

a

‘‘wide

IF

amplifier’

stage

(for

improved

quality

of

sound)

and

a

“nar-

row

IF

amplifier”

stage

(for

better

selectivity).

(See

Fig.

4-15).

The

WIDE

and

NARROW

positions

are

switched

by

switching

the

bias

of

D,,

and

D,;,

thereby

altering

the

signal

path.

In

the

NARROW

position,

D,s

is

turned

on,

resulting

in

the

inverse

biasing

of

D,,,

and

the

IF

signal

being

passed

via

F,

(narrow

band-pass

filter).

In

the

WIDE

position,

the

D,,

bias

is

removed,

resulting

in

D,,

being

biased

in

the

forward

direction,

and

the

IF

signal

being

bypassed

via

D,,.

ANTENNA

HAII97

O

TX-9800

AM

SIGNAL

(

PAIOOI~A)

(PAIO02~-A

)

MPX

OUTPUT

F

MUTE

IC

a

(PAZ00I—A)

FM

IF

SYSTEM

IC

DECORDER

1c

(8)

OFE

D8

+B=O

O

ON

|

MUTING

+B

POWER

TRANSFORMER

Ac

LINE

3}

Fig.

4-13

Muting

control

circuit

POWER

ON

POWER

OFF

oo

!

i

(0)

2

ae

|

v

|

025

ON

©

Ea

POWER

ON

MUTING

POWER

OFF

MUTING

TRIGGER

Fig.

4-14

Voltage

waveforms

a

ee

ep

SIGNAL

METER

PA3ZOOI-A

ARROW

KPA

IO0I-A

+B

AM

°

WIDE

+B

°

IF

BAND

FM

FUNCTION

Fig.

4-15

AM

tuner

11

Pea

SE

EPS

RAAT,

Sere

NR

PAY

PSA

CANT

oe

RR

te

NRA

ee

Pa

5.

DISASSEMBLY

Wooden

Case

Remove

the

two

screws

(A)

on

each

side

of

the

wooden

case.

Bottom

Plate

Remove

the

eight

screws

(B)

to

detach

the

bottom

plate.

Front

Panel

Remove

the

all

control

knobs.

Remove

the

five

screws

(C)

from

the

front

panel.

Wooden

case

Bottom

plate

12

Pioneer TX-9800 User manual

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