Pioneer TX-6800 User manual

AM/FM

STEREO

TUNER

x<-6800

TX-60S

PIONEER

Both

Model

TX-6800

and

TX-608

have

the

same

basic

performance.

The

major

difference

appear-

ance,

Model

TX-6800

being

fitted

with

wooden

side

and

top

panels,

while

Model

TX-608

employs

metal.

MODEL

TX-6800

COMES

TWO

VERSIONS

DISTINGUISHED

FOLLOWS.

Voltage

Remarks

120V

only

U.S.A.

model

120V

only

Canada

model

Voltage

Remarks

120V

only

U.S.A.

model

220V

and

240V

(Switchable)

Europe

mode!

220V

and

240V

(Switchable)

United

Kingdom

model

220V

and

240V

(Switchable)

Oceania

model

110V,

120V,

220V

and

240V

(Switchable)

General

export

model

110V,

120V,

220V

and

240V

(Switchable)

U.S.

military

model

This

service

manual

applicable

the

TX-6800/KU.

When

repairing

the

TX-608/KU,

please

see

page

23,

and

for

the

other

types,

please

refer

the

additional

service

manuals.

CONTENTS

SPECIFICATIONS

..........

0.0.0.0

eae

EXPLODED

VIEW

FRONT

PANEL

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

9.1

Exterior

Components

...........0005

BLOCK

DIAGRAM

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

00005

9.2

Interior

Components............-00%

CIRCUIT

DESCRIPTIONS

;

10.

SCHEMATIC

DIAGRAM,

P.C.

BOARD

4.1

AMTuner....

0...

eee

eee)

RSME

EARS

RD?

SENNCE

wee

sas

bogs

tala

10.1

Miscellanea

...........

00.0002

eee

DISASSEMBLY

...............-

10.2

Schematic

Diagram

......

0...

eee

PARTSLOCATION

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

2...

ee.

10.3

P.C.

Boards

Connection

Diagram

........

DIALCORDSTRINGING................

10.4

Parts

List

P.C.

Board

Assemblies

......

ADJUSTMENTS

Vt.

PACKING

is.

cee

elle

eee

«22

Bar)

PNP

Raner

tns

ubetanin:

Tic

12.

SUPPLEMENTS

FOR

MODEL

TX-608/KU.....

8.2

AMTuner...

2...

0.2...

cee

eee

SPECIFICATIONS

Semiconductors

Section

Usable

Sensitivity

.......

50dB

Quieting

Sensitivity

Signal-to-Noise

Ratio

65dBf

...........

Distortion

6S5dBf......

Capture

Ratio

Alternate

Channel

Selectivity

Stereo

Separation

.......

30Hz

15kHz:

Frequency

Response

.....

Spurious

Response

Ratio

Image

Response

Ratio

....

Response

Ratio

......

Suppression

Ratio...

Subcarrier

Product

Ratio

Muting

Threshold

.......

De-Emphasis

Switch

(Switchable)

Antenna

Input

.........

MONO:

10.8dBf

(1.9uV)

MONO:

15dBf

STEREO:

38dBf

MONO:

80dB

STEREO:

74dB

MONO:

100Hz

0.1%

1kHz

0.1%

6kHz

0.15%

STEREO:

100Hz

0.2%

1kHz

0.2%

6kHz

0.25%

exces

Tice

1.0dB

eon

60dB

1kHz:

40dB

35dB

20Hz

15kHz

*9:8

70dB

60dB

80dB

55dB

50dB

17.2dBF

(4.0uV)

25us

75us

300ohms

balanced

75o0hms

unbalanced

Section

Sensitivity

IHF,

ferrite

antenna

{HF,

external

antenna

Selectivity

2.0...

en55

Signal-to-Noise

Ratio.

....

Image

Response

Ratio

Response

Ratio

......

Antenna

.......0.0005

Audio

Section

Output

Level

Miscellaneous

Power

Requirements

.....

Power

Consumption

.....

Dimensions

...........

Weight

(Without

Package)

Furnished

Parts

T-type

Antenna

......

Connection

Cord

with

Plugs

Operating

Instructions

.....

NOTE:

TX-6800

300unV/m

15yuV

35dB

50dB

40dB

70dB

Built-in

Ferrite

Antenna

650mV/4.3kQ

(FM

100%

MOD.)

120V

60Hz

14W

451(W)

x151(H)

284(D)

17-3/4(W)x

5-15/16(H)

x11-3/16(D)

5.3

(111b

110z)

Specifications

and

the

design

subject

possible

modifica-

tion

without

notice

due

improvements.

FRONT

PANEL

FACILITIES

ARPPER

FPP

100

ADK

@PIONEER

STEREO

TUNER

TX-6800

POWER

SWITCH

Set

this

switch

supply

power

the

tuner.

SIGNAL

METER

This

meter

indicates

the

antenna

input

level

the

and

broadcasting

waves.

The

higher

the

input

level,

the

meter

deflects

to-

ward

right.

When

selecting

the

desired

station,

find

the

position

the

tuning

knob

which

effects

the

maximum

deflection

the

meter

pointer.

When

selecting

station,

also

observe

the

tuning

meter

determine

the

optimum

tuning

point.

@®

TUNING

METER

This

meter

indicates

the

optimum

tuning

point

irrespective

the

field

strength

when

selecting

station.

With

signal,

the

pointer

remains

the

center;

signal

tuned

in,

deflects

the

right

left;

when

the

signal

tuned

accurate-

ly,

the

pointer

will

correctly

move

the

center

the

scale.

the

tuning

knob

adjusted

fur-

ther,

the

pointer

deflects

the

right

left;

the

signal

moves

off

completely,

the

pointer

re-

turns

the

center

position

again.

FUNCTION

INDICATORS

These

indicators

light

during

re-

ception,

respectively.

@®

STEREO

INDICATOR

This

indicator

lights

when

the

tuner

receiv-

ing

stereo

program

the

muting/mode

switch

set

ON.

DIAL

POINTER

This

pointer

indicates

the

broadcasting

stations.

FUNCTION

SWITCH

This

switch

used

select

the

type

broad-

casting

waves.

.......

For

reception

broadcasting

.......

For

reception

broadcasting

MUTING/MODE

SWITCH

When

this

switch

set

ON,

unpleasant

intersta-

tion

noise

eliminated,

which

makes

selection

stations

easier.

However,

the

muting

switch

set

areas

where

the

field

strength

ex-

tremely

weak,

the

station

being

received

may

also

disappear.

such

areas,

therefore,

the

muting

switch

should

turned

(MONO).

When

this

switch

set

OFF

(MONO),

monaural

recep-

tion

will

obtained

even

though

the

station

broadcasting

stereo

program.

TUNING

KNOB

This

knob

used

for

selecting

station.

When

selecting

station,

observe

the

signal

meter,

and

when

selecting

station,

observe

both

the

signal

meter

and

the

tuning

meter.

TX-GS00

BLOCK

DIAGRAM

DEMODULATOR

MIXER

SCOR

esate

@®®

hive

CERAMIC

FILTER

AMO—

rae

|LOCAL

DE-EMPHASIS

TUNE|

OSC.

SIGNAL

TUNING

}

rene

TUNING

(STEREO/MONO)

75/25us

‘@

Lo]

STEREO

BAR-

ANT.

--——-JLC

TUNE

TRANSFORMER

abl

FUNCTION

RECTI~

oy,

V.R.

Ord

OS)

(AM

OSC)

CONTROL

FIER

‘@

ILLUMINATION

eee

OS)

FUNCTION

(6)

(©)

(C)

LAMPS

HNVULEYUOUAUUVTQQUDUANIQUEDLUUOUUCUQUDULTUUUUTVOCUALLSTHUOOUTTUUUEOOEUCOOU

QUAN

UTOOEUUPEG

TAO

EAOT

VCORE

CIRCUIT

DESCRIPTIONS

4.1

TUNER

The

tuner

employs

2-ganged

tuning

capaci-

tor,

single-element

ceramic

filter,

and

(HA1138)

consisting

amplifier,

mixer,

2-stage

amplifier,

detector

and

AGC

amplifier.

See

Fig.

4-1

for

the

block

diagram.

When

the

FUNCTION

switch

(S3)

the

position,

applied

the

emitter

Qi:

via

Rs2,

Re2

and

Res.

Qii

will

turn

off,

and

the

local

oscillator

circuit

will

opened.

Fig.

4-1

tuner

4.2

TUNER

Front-End

frequency

linear

3-gang

variable

capacitor

used

with

single

stage

FET

amplifier.

The

FET

possesses

high

input

impedance

com-

pared

with

transistor,

and

allows

simple

coupling

with

the

input

tuning

circuit,

plus

significant

ad-

vantage

terms

noise.

The

local

oscillator,

employs

modified

Clapp

circuit,

thereby

reducing

the

amount

drift

caused

changes

time,

ambient

tempera-

ture,

and

power

supply

voltage.

Also

since

the

oscillator

signal

obtained

from

the

tuning

circuit,

there

are

far

fewer

higher

harmonics,

resulting

much

cleaner

waveform

with

less

spurious

inter-

ference.

The

oscillator

signal

applied

the

base

the

mixer

transistor

Q2.via

low

capacity

capacitor.

When

the

FUNCTION

switch

(S3)

the

position,

applied

the

cathode

via

R34.

will

cut-off

and

will

turn

off.

AMP.

MIXER

IFT

Fig.

4-2

front

end

Amplifier

and

Detector

This

stage

includes

dual-element

ceramic

fil-

ters,

transistor

and

(PA3001-A)

with

high

ratio

and

very

little

distortion.

The

transistor

inserted

between

the

two

ceramic

filters

employ-

for

impedance

matching

purposes

well

increase

the

gain.

PA3001-A

includes

the

limiter

amplifier,

detector

(quadrature

detector),

amplifier,

muting

circuit

and

the

meter.

drive

circuit.

The

muting

circuit

turned

when

pins

and

are

connected

means

the

MUTING

switch.

the

dial

pointer

moved

approx.

+70kHz

away

from

station,

and

the

input

level

very

low

(equivalent

antenna

input

less

than

4uV),

signal

generated

12,

and

applied

thereby

activating

the

muting

circuit

within

the

IC.

MPX

Stereo

Demodulator

The

(PA1001-A)

employed

the

multi-

plex

stereo

demodulator

stage

also

features

high

SN:

ratio

and

reduced

distortion.

Due

the

in-

corporation

pilot

auto-canceller

circuit,

very

good

frequency

characteristics

are

obtained.

Un-

the

conventional

pilot

signal

(19kHz)

canceller

circuits,

which

fail

completely

remove

the

pilot

signal

not

standard

level,

PA1001-A

pilot

auto-canceller

circuit

also

includes

pilot

signal

level

detector

circuit.

Changes

pilot

signal

level

are

consequently

responded

immediately,

resulting

very

effective

suppression

the

pilot

signal

leak

level.

Filter

Circuit

Besides

eliminating

the

sub-carrier

signals

(more

than

23kHz),

this

PNP

transistor

18dB/oct.

active

filter

also

serves

amplifier

for

the

low-pass

region,

and

crosstalk

canceller.

TX-6800

DISASSEMBLY

Side

Panels

and

Top

Panel

Remove

the

four

screws

(A),

and

remove

the

side

panels.

Bottom

Plate

Remove

the

screw

(B).

Front

Panel

Pull

off

all

the

knobs,

and

remove

the

four

screws

(C).

Top

panel

Side

panel

CG.

wAanmal

panel

Front

panel

Bottom

plate

n¢a—

PARTS

LOCATION

The

mark

found

some

component

parts

indicates

the

importance

the

safety

factor

the

part.

There-

fore,

when

replacing,

sure

use

parts

identical

designation.

Front

Panel

View

Side

panel

Side

panel

AMS-033

AMS-034

Front

panel

ANB-721

Knob

(TUNING)

AAA-058

Knob

(POWER,

FUNCTION,

MUTING)

AAD-183

Front

View

with

Panel

Removed

LED

(AM,

FM)

AEL-319

TUNING

Taytee

eieueree

LED

(STEREO)

AEL-315

A\Lever

switch

(POWER)

ASK-514

Tuning

shaft

assembly

AXA-228

Lever

switch

(FUNCTION)

Lever

switch

(FM

MUTING)

ASK-155

ASK-157

’

De-emphasis

assembly

Top

View

GWS-188

Tuner

assembly

Fuse

assembly

GWM-135

AWR-200

Power

transformer

ATT612

Fuse

(1A)

Switch

assembiy

AEK-106

GWS-187

Lamp

(wedge

type)

Rear

Panel

View

AEL-029

Top

panel

Bar-antenna

AMS-035

ATB-505

Antenna

holder

AXB-012

Terminal

(OUTPUT)

AKB-062

power

cord

ADG-023

Terminal

(ANTENNA)

Slide

switch

(DE-EMPHASIS)

AKA-014

ASH-015

DIAL

CORD

STRINGING

Remove

the

wooden

case

and

front

panel

described

the

‘Disassembly’?

section

page

Turn

the

tuning

capacitor

shaft

fully

clockwise.

Fix

the

tuning

drum

the

tuning

capacitor

shaft

that

the

set-screw

uppermost.

Tie

end

the

dial

cord

the

hook

the

tuning

drum.

Pass

the

cord

through

the

cut-out

section

the

tuning

drum,

and

then

take

over

pulleys

and

that

sequence.

Wind

the

cord

around

the

tuning

shaft

times.

Pass

over

pulley

wind

around

the

tuning

drum

times,

and

finally

tie

the

spring

hook

that

tensioned.

Tuning

drum

11.

12.

138.

TX-6GS00

Turn

the

tuning

shaft,

and

check

that

the

cord

moves

smoothly.

Cut

off

any

excess

cord.

Turn

the

tuning

shaft

counter-clockwise

far

will

go.

Align

the

dial

pointer

with

the

starting

point

the

dial

scale

(second

division

from

the

left),

and

then

pass

the

cord

over

it.

Check

that

the

dial

pointer

line

with

the

starting

point

the

dial

scale.

Finally

apply

the

locking

paint

the

cord

securing

positions

(tuning

drum

hook

and

spring

hook)

and

the

dial

pointer

connection.

Tuning

shaft

AAA

ADJUSTMENTS

8.1

TUNER

Connect

the

(FM

signal

generator)

the

ANTENNA

30002

terminals

via

3000

dummy

antenna.

Switch

the

FUNCTION

selector

the

position,

the

MUTING

switch

the

OFF

position.

The

tuning

coils

the

front

end

dose

not

have

adjusting

core.

Consequently,

tracking

adjustments

90OMHz

are

performed

regulating

the

gap

between

rotor

and

stator

the

tuning

capacitors

(VC1,

VC3

and

VCs).

The

expression

“adjust

(VC:i,

VC3,

VCs)

found

the

text

means

that

the

two

outer

rotor

blades

each

these

tuning

capacitors

are

extended

out-

wards

with

spatula

(Part

No.

GGK-066)

shown

Fig.

8-1.

Stator

Rotor

blade

Stator

Rotor

blade

Spatula

(GGK-066)

Fig.

8-1

Adjustment

tuning

capacitor

Set

the

TX-6800

dial

point

frequency

the

106MHz

region

that

there

will

input

signal.

Rotate

the

core

bring

the

TUNING

meter

indicator

dead

center.

tune

accurately

1O6MHz,

and

set

the

output

106MHz,

80dB

(modulation—400Hz,

+75kHz

deviation).

Adjust

TCs

obtain

maximum

deflection

the

SIGNAL

meter

indicator,

and

dead

center

reading

the

TUNING

meter.

Then

tune

the

dial

pointer

90MHz,

and

set

the

output

frequency

90MHz.

Adjust

the

VCs

obtain

maximum

deflection

the

SIGNAL

meter,

and

dead

center

read-

ing

the

TUNING

meter.

Repeat

steps

above.

Reset

the

output

level

20—30dB,

and

adjust

TC:

and

TCs

106MHz,

‘and

VC:

and

VCs

90MHz

the

same

manner

described

above

steps

These

ad-

justments

will

ensure

optimum

sensitivity

the

106MHz

range,

and

minimum

dif-

ference

sensitivity

between

the

two

extreme

frequencies.

Retum

position

with

input

signal.

10.

Rotate

the

core

again

set

the

TUNING

meter

indicator

dead

center.

11.

Set

the

output

98MHz

and

66dB

(modulation—400Hz,

+75kHz

deviation),

and

tune

the

TX-6800

this

position.

12.

Then

rotate

the

core

reduce

dis-

tortion

the

demodulator

output

(OUTPUT

terminal)

minimum.

18.

Repeat

steps

above

until

both

specifi-

cations

(center

TUNING

meter

reading

the

absence

input

signal,

and

minimum

dis-

tortion

demodulator

output)

are

satisfacto-

rily

met.

Multiplex

Decoder

Connect

the

MPX

(FM

multiplex

generator)

the

external

modulator

terminal.

Set

the

MUTING

switch

the

position.

14.

Set

the

output

98MHz

and

66dB

(unmodulated),

and

tune

the

TX-6800

this

position.

15.

Adjust

VR:

obtain

76kHz

signal

terminal,

16.

Then

set

the

output

level

86dB,

and

the

modulation

mode

external.

Then

with

the

MPX

SG,

set

Main

1kHz,

L+R

+67.5kHz

deviation,

and

pilot

signal

+7.5kHz

deviation.

17.

Rotate

the

core

around

90°

either

direction

reduce

the

demodulator

output

(OUTPUT

terminal)

distortion

minimum,

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