Pioneer SX-3900 Service manual

$eftice

nual

FM

€Iuartz

STEREO RECEIVER

Locked

six-3s|oo

()proNEER'

MODEL SX.3gOO

Type

KU

COMES

120V

only

IN

VERSIONS

TWO

Voltage

DISTINGUISHED

U.S.A.

AS

model

FOLLOWS:

Remarks

5/U

This service

additional

service

I 10V,

manual

manual

CONTENTS

1.

spECtFtcATtoNS

FRoNr

2'

BLocK DIAGRAM

3'

PANEL

4. clRCUlr

FM Tuner

4.1
AM Tuner Section

4.2

4.3 Audio Section
DisplayCircuits

4.4
Protection Circuit

4.5

4'6 Surge

DISASSEMBLY

5'

PARTS LOCATION

6.

7. DIAL
g.

9, SCHEMATIC

10.
I1.PARTSLIST.

12.

13.

ADDTTTONAL

CORD STRINGING

ADJUSTMENTS

Audio Section

8.1

Tuner Section.

8.2

p.c.

BoARDS

EXpLoDED

PACK|NG....

FACILTTIES

DESCRIPTIoNS

Section

current suppressor

' '

DIAGRAM

coNNECTToN

vtEW

SERVTCE

22O and

120V,

is applicable

(see

pages

.

DTAGRAM

MANUAL

FOR

240V

to

47

.......

" " "

S/G

(Switchable)

the KU

type.

-56l..

'

TYPE 41

2

a
7

8
9

9
11
13

l5

1E

15
16
18

1e

20
24
29
35
41
46

model

Military

U.S.

please

When

1.

repairing

the

SPECIFICATIONS

S/G

type,

Power Amplifier Section

Continuous

nel, min.,

Hertz

diStOftiOn.

niC

Harmonic

To,rl

g

ohms)

continuousratedpoweroutput..

watts

60

Power

at

0utput

8ohms

with n0 m.re than 0.005% tolal

Distortion

per

channel

power

,",1r',jlltr,r.ion oirioriion

power

continuous

watts

60

output

Frequency

rated

per

channel

Response

power

0f

from 20Hertz to 20,000

(20

Hertz

rrrrrltrl;f

iuo

output

. . . ' No more than 0.005%

'

rnpr.s.nriiiui,vli,.np.oun..t,i;ff

. . . . .

OUtPUt

-speaker
Damping

Hr..;;

Preamplifier

(Sensitivity/lmpedance)

I

nput

PHONO
AUX, TAPE

ADAPTORIN

Phono

Overload

PHONO

(

OutPut

Total Harmonic

Level/l

REC 1,

TAPE

PREAMP

PHONO

Factor

rtr.ir.

iiHi,

Section

. .

1,2.

PLAY

1.2...
mPedance)

2.

OUT

(REC

1.2

(20

...

Level

ADAPTOR

(RL:

Distortion

Hertz

1,

OUT) . . .

' ' ' '

to 20,000

...60

rrrortcircuiteo,

""'

2,

... 150mV/50kilohms

(T.H.D.

50

. . .

0.005%,

OUT

kilohms)

1Vl1

.

(20

Hertz to

. . .

the

see

120

wattsxper

chan-

harmo-

to 20,000

Nomorethan0.005%

Hertz,

;::ltjT:"fl

No more than

. .

iorTln?,t'.2

T

'l

V/50

A' B' A+B

'

Hertz, 8 ohms)

network)

A

115d8

2.5mV/50

1,000

300mV

150mV

kilohms

(Volume:

20.000
No more than 0.005%
(10V

output)

0.005%

kilohms

kilohms

Hertz)

Hertz)

*!

aa

max.)

sx-3900

AUX, TAPE

PLAY

1,

ADAPTOR

2.

IN

No more
(10V

output)

Frequency Response

(R

PHONO

AUX, TAPE

Ton.

contror

BASS .

TREBLE

Equalization)

IAA

.

PLAY

1,2, ADAPTOR OUT

' ' ' ' ' 7 Hertz to

. . 20 Hertz

to 20,000 Hertz

80 000

!4dB/!7dB (100H2)

f u rnover F requency

+gdB/t7dB

:

Tu rnover Frequencv

Filter

LOW. .

HIGH

.

Loudness Contour

Hum and Noise

PHONO

AUX,TAPE

(Volume

. . . .

(lH

F,

PLAY

control set

(100H2),

+6dB

short-circuited,

. .. . .. 86dB

1,2,

ADAPTORIN...

Attenuator.
FM

Tuner

Usable
50dB Ouieting

Section

Sensitivity

(lH

Sensitivity

F

)

MONO

STEREO

Signal-to-Noise

Ratio

MONO

EO

STE R

Distortion

MONO

(at

65dBf

100H2.

)

lkHz .

6kHz '

STEREO 100H2.

ikHz .

6kHz

Capture Ratio. . 1.0d8
Alternate Channel

400kHz

Stereo Separation

1kHz.

3OHzto15kllz.

Frequency Response

Selectivity

......80dB

......50d8

...... 35dB

(-6dB/oct.)

15Hz

(-6dB/oct.)

8kHz

-40dB

at

+3dB

A network)

1 05dB

-20d8

(1.7pV)

9.8dBf

14.2dBf
(34.7pV)

36dBf

(at

83dB

(at

78dB

0.1o/o

o.o7%
oJ%

O.27o

o.15%
O.2To

....2OHzto15kHz1!jaa

Spurious Response Ratio . .

lmageResponseRatio ... 90dB

lFResponseRatio.. .... 100d8

AMSuppressionRatio
SubcarrierProduct

SCARejectionRatio .... 64dB

Muting Threshold 19.2dBf
Antenna Input

Ratio

. 300 ohms balanced,

. . . . .

. . . . . . . 64dB

100dB

... 60dB

75 ohms unbalanced.

than

0.005%

t0.2dB

+9

Hertz

dB

2OOHz/ 400H2

(10kHz)

:

2kHz I

4k{z

position)

(10

000H2)

(2.8pV)

65dBf)
80dBf)

(SgV)

AM Tuner

Sensitivity

Selectivity
Signal-to-Noise

lmage
lF Response Ratio.

Antenna

Audio

Output ( Level/l

FM

AM

Section

(lH
(lHF,

Response

Section

(100%

Mod.).

(30%

Mod.)

F, Ferrite

Ext.

antenna)

Ratio

Ratio

.

mpedance)

.

Semiconductors
lCs...

FETs.

Tra nsistors

Diodes
M

iscellaneous

Power

Requirements

Power

Consumption

Dimensions

Weight

(without package)

Furnished Parts

Operating instructions

FM

T-type

antenna

*

Measured
Regulation rule

NOTE:
Specifications and the design
without notice due

pursuant

on

to

the

Power

to improvements.

antenna)

Federal

Output

Claims for

subject to

. .

300sV/m

.

1

SpV

"

30dB
50d
40dB

40dB

Ferrite

a ntenna

650mV/2.4
20OmV

t5

o

89

62

AC

120V.60H2
350W
526(W)
452(D)
20-11/16(wl

(H)

x
2Okg

1
1

Trade

Commission's Trade

Amplifiers.

possible

B

loopstick

kilohms
kilohms

/2.4

(UL)

x

176(H) x

mm

x6-1 5/16

17-14/16(Dl in

(441b

2ozl

modifications

2.FRONT

PANEL

FACILITIES

POWER

O

SetthisswitchtooNtosupp|ypowertothereceiver.
There

the

unpleasant
Power

BASS

@

Use
the
to

withthecharacterlstics'ofyourIisteningroomandof
your

EASS

@

Use
lf
controItotherightfromitscenterposition,youwi||be

ab|etoemphasizethesoundinafrequencyrangewhich
is
Conversely,

to
You

frequency
over

TONE

@

Set

controls.
circuitsaredisengagedandfrequencyresponseisf|at.
Thisfunctionisconvenientforcheckingphonocartridge

and

SWITCH

a

be

will

muting

circuit

noise

is switched

TURNOVER

switch

this

adlustment

sound

effect.

take

speakers,

AND

controls

these

set

than

left

use

can

switch.

the

turning

will

the

higher

you

lower

the

SWITCH

switch

this

When

speaker

delay

short

been

has

is

that

and

on

change

to

with

200H2

Select

your

with

and

TREBLE

to adiust

switch

tone

selected

that

this

attenuate

treble

than

when

to ON

the

to

set

quality and

tone

is set

it

when

actuated

sometimes

'

off

generated

SWITCH

frequency

the

over

bass

the

400H2

or

general

preference'

CONTROLS

bass

the

ON

to

bass

the

by

sound'

the

selected

adjusting

OFF

from

adjust

to

position' the

listening

control

control
that

ON'

to

suppress

to

control

in

and

turn

and

turnover

center

the

the

by the

bass

the

room

because

the
the

when

which

in

starting

is

accordance

treble'

the

bass

the

switch'

position

in

sound

turn-

treble

treble

and

control

tone

acoustics'

TREBLE

O

this

Use

sound

the

take

to
withthecharacteristicsofyourIisteningroomandof

your

noRProR

@

TURNOVER

switch

adjustment

effect'

speakers,

and

change

to

Select

with

swlrcH

SetthisswitchtooNwhenreproducingsoundfroman
optional
TOR

not

@

Set
edit

@

Employ
progress.

1:

a

SOURCE:

2:

component

iacks.

using

TAPE

switch

this

pre-recorded

a

TAPE

NOTE:
When
switch

set

is

if it

Always

component

a

set

DUPLICATE

ON

to

MONITOR

playback

tape

for

Playback

to

nected

sure

Be

the

using

ng '

tori

Playback

to

nected

records

listening
to

to

SOURCE'

2.

or

1

to

SWITCH

over

the

with

2k{z

general

your

is

which

the

to

it

these

with

SWITCH

when

using

tape

SWITCH

or

monitoring

or

TAPE

the

set

to

deck

tape

monitoring

or

TAPE

the

or
witt

Sound

frequency

the

control

treble

4kHz

or

preference'

connected

position

upper

terminals'

you

want

tape

two

monitor

to

of

jacks'

1

position when

this

to

playback

for

of

jacks'

2

broadcasts'

obtained

be

not

is starting

accordance

in

the

to

duplicate

to

decks'

recording

a

tape

a

tape

a

sure

be

from

which

in

ADAP-

you

if

deck

and

deck

to

are

or

in

con-

not

moni-

con-

this

set

speakers

six-39cl(f

BALANCE CONTROL

€)

Use

this control to balance
right channels.
MONO. lf
means that the volume

the

Turn
versely,
means that the volume
Therefore.
ad
STEREO.

@

Use this
a nces .
STEREO: Set to this
MONO:

o

Use

speakers and headphones. Turn
the output level. No

-.
attenuation when

€)

Set this switch
audio
There is no
this
porarily

G)

Plug
listen
Release both speaker
the sound

(E

Depress the switch corresponding
nected
panel.
You
sound
time.

if

just.

After

MODE

voLUME CONTROL

this control

The

MUTING

output indicated by

switch when

and when

HEADPHONE

the

through

SPEAKER SWITCHES

to the SPEAKERS

can

from two

First,

however,

the sound

balance control to
the

turn the balance

appears to be louder

of the right

appears

sound

of the left channel is

adjusting, return

SWTTCH

for

switch

When
channel
duced monophonically from
systems.

scale

selecting mono or stereo

position

set to this

signals will be mixed

to adjust the

sound will be heard if

graduated

is

the maximum

SWITCH

*20d8

to the

the volume

need to adjust

turning down
changing

the volume

over records

JACK

headphones

your

through

depress

into this

headphones.

stereo

switches

your

headphones

terminals

both of

pairs

these

of speaker systems

the volume of

set the mode

left

the

to be louder

control to the right

the mode switch to

for

position,

output level to the

it clockwlse to increase

in dB which indicate

output

position

the audio output

jack

when

you

if

only.

to the speakers

(A

buttons to

the left

switch to

on the right,

channel is higher.

and adjust.

the left,

on

higher.

perform-

normal

operations.

the left

control

control

want

and right

and

both speaker

you

set it to

level

is 0dB.

to attenuate

by 20dB.

you

if

or tapes.

you

want to

to listen

B)

or

on

listen to the
at the same

repro-

the

and

Con-

and

the

the

use

tem-

to

con-

rear

LOW FILTER

@

Depress this
recording

it

it

becomes objectionable. Attenuation in
band

HIGH FILTER

G)

Depress
frequency
the

POWER

€)

This meter allows
on

nominal impedance

speaker

DrAL

@

This

rnn

@

cutting noise or

below

this

noise

frequency

fluorescent

the

terminals.

POTNTER

pointer

STEREo

SWITCH

switch in the event that turntable rumble,

15Hz is 6dB/octave.

SWITCH

if record

switch

becomes objectionable. Attenuation in

band

above

METER

you

display

of 8 ohms are connected

indicates

the broadcasting

rNDrcAToR

This indicator lights up when receiving
program

@

This indicator lights up
has been obtained and displays
stabilized

SIGNAL

€D

This indicator lights in
during
ance with the strength of
The optimum tuning
number of indicators

rururNG

@

When tuning in
point

When

knob

on,

@

This indicates the
With FM reception,
of
tion,
These change
cha nged.

if

FM

the

oUARTZ

by

muting off

LOCKED

built-in

the

INDICATOR

the tuning of an AM or

light.

rNDrcAToR

FM

an

is indicated

left indicator has

the

slightly clockwise. When the right indicator comes

rotate the

FREOUENCY

the display and

"AM"

when

knob

slightly

DISPLAY

frequency

the

"MHz"

appears on the

when

the

(15H2)

low frequency noise

other

frequency

the

(8kHz)

scratch noise or other high

is

SkHz

to read out

tube

switch

6dB/octave.

rated

the

when

speakers

stations.

an

is released.

power

FM

|ND|CATOR

after the optimum tuning

that the receiving state is

quartz

lock

circuit.

sequence

point

station, the optimum

the

letters

from

left through

FM

broadcast

the signals

is where

center

come on,

counter-clockwise.

which is tuned.

"FM"

on the

left

and

function

being received.

the maximum

indicator lights

rotate

appear on the

right. With AM recep-

"kHz"

on the

selector

in

reception

the

position

level
with a
to the

stereo

point

right

accord-

up.

tuning

left

right.

is

TUNING KNOB

@

Use this

knob

to

tune

broadcasting

in to

stations.

5

MUTING

FM

@

this

When

muting

the

in,
annoying
frequencies

station

ing

area,

fringe

lf there

in.

tune

level

signal
you

want

satisfactorily

stronger

the

by
MUTING

The

in.

tune

receiving

is

tuner

performed

depressed

circuit

indicator

@

Depress

broadcast;
position.

@)

is

does

25PS

FM

BRIGHTNESS

this

Use

and

meter
BRIGHT:

DIM:

*Theword,,Dolby''isatrademarkofDoIbyLaboratoriesInc.

OFF

released

is

switch

is activated

circuit

interstation

for noise-free

far away

is

switch

tne

set

broadcasting

a

is

air

the

on

signals'

switch

AM

the

station

a

the

to

light.

not

you may

FM

receive,

to

because

OFF

muting

after
and

set

SWITCH

switch

this

otherwise

SELECTOR

select

to

switch

frequencY

the

using

When

locations'

bright

night

At

brightness

ing

SWITCH

and

between

noise

reception'

when

or

the

to

a

to

next

sound

the

cases

In

(depressed

OFF

to

circuit

when

or

does

broadcasts'

MUTING

selected.

mode

F

OF

listening

this

keep

the

disPlaY'

receiver

the

dark

in

is too

FM broadcast

an

to

inside

the

the

When

position

station

whose

able

be

be

this'

like

work

not

tuning

lf

switch

OFF

the
and

to

daylight

in

a

with

drowned

quartz locked

the

a

at

when

receiving

OFF

station

not

will

switch

brightness

locations

high'

tuned

suppress

broadcasting

station

set

position) and

of

the

broadcast-

in a

then

and

strong

a

program

tune

to

out

FM

the

the

when

been

has

been

has

LOCKED

released

power

the

or

the

FM

other

exist-

Dolby*

the

in

FUNCTION

@

Deoress
program source.

before
sound

the

selecting

from one

FM:

AM:

AUX:

PHONO

PHONO

@

When
control

When

2:

1:

NOTE:

one

OnlY

LOUDNESS

listening

turned

treble

and

the

the

hear

loudness

The

iciency.

def

this

come

treble

on

takes

down.

turned

SELECTOR

function

Turn

different

a

program

Depress
Deoress

Depress
audio
iacks.

Depress

the

jac

function

this

this

component

this

turntable

k

s.

Depress

turntable

the

acks.

i

switch

SWlrcH

to

down,

accentuated'

be

will

and

switch

through

puncn

a

is

By

volume

bass

which

switch

volume

the

function

source

switch

switch

switch

this

switch

connected

switch

this

connected

should

performance

a

depress

human

the

low,

than

treble

designed

is thus

depressing

more

much

when

even

corresponds
control

switch

reproduced'

being

is

FM broadcasts'

for

broadcasts

AM

for

listening

when

connected

playing a

when

the

to

playing

when

the

to

depressed

be

with

switch

this

f

inds

ear

the

when

to

switch'

this

strongly

volume

the

the

to

first

down

the

while

to

AUX

the

to

record

PHONO

record

a

PHONO

ilme'

a

at

volume

the

bass

the

and

it harder

high'

the

and

is

bass

sound

the

control

volume

compensate

an

on

2

on

1

to

for

and

is

sx-39clcl

BLOCK

3.

Tuner

Section

AMO

AM TUNER

DIAGRAM

(

HAl2010

rc

5-POINT
INDICATOR

CoUNTER
TIME
7­ROM

)

SIGNAL

ORIVE

DIVISION

SE6M€NT

s1 s2 s3 s4

Oi - D5

OECOD€R

rUN]NG INDICATOR

FREOUINCY

OISPLAY

FM MHz

,ODDD

t_,

,

t_t.t_t t_t

AM

KHT

OUARIZ

LOCKEO

Audio

Section

IAPE 1

REC PLAY

.":-

ADAPrcR

_-. ^

IN

OUT

R CnANNE- . IHL SAME

A5

FREA!ENCY

IHF

L CHAN\EL

ar

lr

)

FL TUSE

'UIER

SECTION

CIRCUIT

4.

TUNER

FM

4.1
End

Front

front

FM

The
ganged
Eo"Too"A

ai;;

uoiiug"

(varia'ble
,yrt"..t
operution,

tuning

l-slage

circuit

controled

capacitance

(refer

a

diode.

Amplifier

lF

These
filters.
stitutes
ii-lti.rg

stage,
liigool

quadrature

cuits.
ratio,

,ho*,
the

employ

lC

fne

single-stage

a

limitet.

improvement

an

ai,

detector,

Performance

delay

marked

a

PA3001-A.

Ouartz-Lock

quartz-lock

The

stereo

employing
i.r
DC

receiver

a

itt"-lntlrmediate

voltage

crystal

resonator)'
ir"qt"r-r"y
locked.

trol
remain

This

system

tuned

When

the

FM

DESCRIPTIONS

SECTION

SX-3900

of

end

dual-gate

capacitor,

RF

llcal

oscillator

to

"Quartz-lock

constant

Detector

and

ICs

3

(HA1201)

The

includes

characteristics,

improvement

SYstem

a

is

crystal

the

by

being

extremely

thus

securely

signal

IF

END

FRONT

a

amplifier'

oscillator'

diode)'

voltage

3

and

of

differential

(PA300?-A)-in

IC

the

on

an

meter

terms

in

system

featured

frequency

resonator'

frequency
discriminator
resulting

corrected

stable

for

that

as

ensures

appears

includes

MOS

modified

a

and

oscillator

This
employing
When

a

the.quartz-lock

system")

applied

is

dual-element

stage

2

first

the

amplifier

former

iF

drive'

and

serl/o

iF system

iimiter

and

distortion'

of

other

comparison

in

the

in

control

displacement

Any

detected

is

(IF)

parameters'

(equipped

local

the

in

subsequently

and

frequency

tuned

long

at

frequencies

required'

as

pin no'17

4

a

FET-

a

is

vari-cap

to

in

the

is not

ceramic

con-

current-

third

the

IC

amplifier'

other

cir-

S/N

to

SX-3900

system

as

with

oscillator

con-

servo

the

of

IF system
ptiei to
sists
resonance
i.r.

fr"qr".r"y

it

at
fut

iruq.r"rr"y

tanie

ir"rar"tun"u
Jetection

the

of

L stage
tance
which
it'r"

degree
in&eased,
the

characteristics,

Since
tiorl-a""
about

equal
o,rt
displacement

deviation
aryrrr-utri"a1,

"liiug".

(IF filter)

a
a

iion
tancediodeinthelocaloscillator,therebycorrect­ing

tn'
tor

frequencies
tained.

IC

crystal

a

diodes

of

circuit

resonance

irt"

(10'?MHz),

time

ls

reduced

being

increases-

(C) is

stage

by

IF signal.

reactance

increased,

leaves

t stage

oidetuning

resulting

detector

IF signal

the

to

central

a

the

to

level

OC

in

This

voltage

oscillator

the

constant

(i.e.

a

the

Since

regulated

is

(PA300?-A),

detector

connected

equipped

frequency

which

minimal,

be

will

a

to

the

reduced,

stage

(L) increased,

which

D2

If the

decreased

is

resulting

negative

the

C stage

and

in

in

output.

detection

FM

is an

iodulation,

And

axis.

resonance

zero.

be

will

central

the

in

respect

resulting

voitage

DC

LPF2

and

which

is applied

frequency

tuned

central

frequency

by

exiremely

of

is amplified

it

Fig'

(see

parallel

in

with

is

means

resulting

minimum

reactance

the

and

leaves
input

the

frequency

AM

in

portion

reactances

respective

the

subsequent

a

thus

By

signal

FM

will

it
the

if

frequency,

however,

If,

frequency,

detector

the

to

the

in

passed

is

filter)

(AC

to

to

frequency)'

crystal

the

high

lc

and

which

4-1)

a series

in

crystal

a

as the

same

the

impedance

the

the

in

If the

level'

the

of

reactance

resulting

positive

decreases'

C stage

and

detection

IF signal'

the

of

inctease

directions

increase

attaining

becomes

frequency

be symmetrical

central

frequency

detector

the

there

frequency

will

generation

through

form

to

variable

the

the

a

crystal

obtain

of

resonator'

stability

(

PA 5007-A

)

ap-

con-

resona-

IF

out-

input

capaci-

the

of

AM

in

portion

reac-

D1

by

the

as

is

in

S-curve

possible'

devia-

is

out-

is any

become

DC

a

of

LPF1

correc-

a

capaci-

constant

detec-

tuned

ob-

are

CRYSTAL

| ----, I
:(L) 13

IT

C IRCU

SYstem

Ouartz

4-1

Fig.

a

Lock

DETECTOR

+i

sx-39clo

o

Limiting the
If

the

overlap with strong adjacent

quencies
culties.
limiter
which restricts the
capacitance diode, thereby
range.

system
ievel drops below 5pV, or when the

quency

This

the
ing in

Iock
Multiplex

(PA4006-A)
functions in
functions
(PA1001

further improved by incorporating a chopper
MPX
(see
either to
eliminating the
distortion.
tures
tor, there
Iow frequency end.

PA4006-.4

ler, stereo auto selector, VCO killer circuit,

amplifier. and

Inprt

A DC

(limiter

A DC voltage

IC

has

DC voltage

gate

of

the

circuit being turned off.

The

recently developed multiplex

Distortion

decoder. The chopper type switching circuit

Fig.

DC

Besides the decoder and muting circuits, the

switchins

Fig.4-2

Locking Range

quartzJock

and result

amplifier

action

(PA3007-A)

been detuned by

(FET)

Q2

FET

Decoder

combines

a single

of the more conventional

A)

and

ratings and S/N ratio have been

4-2) operates by switching the signal

ground

generation

Furthermore,

direct-coupled switching with the detec-

is

no deterioration in separation at the

also incorporates the

MUT control

Composite

s ignal

JUIIUUUIJUIJU'

,in"r'r

Chopper Type Switching Circuit

range is

in considerable

by NFB circuit

voltage

appears at

when

(FM

muting signal) is applied to

via a Schmitt

being turned on, and the

MPX

IC,

AF MUTING

or to the through circuit, thereby

since the

S/

too wide, it will

broadcasting fre-

tuning diffi-

is

therefore used as a

zener

diodes)

applied to the

limiting

decoding with muting
thereby

of unwanted noise or

circuit.

.}. I

nL

the

pin

no.13 of the

antenna input

the

more

than

(PA1002-A).

IC

PA4006--4

pilot

--'I

variable

quartz-lock

tuned

t100kHz.

circuit,

quartz-

decoder

handling

MPX IC

signal cancel-

Output

IF

fre-

result-

IC

the

type

fea-

MU'l

4.3 AUDIO
Phono Equalizer

Fig.
circuit. An S-N ratio
IHF-A)

PNP

noise

and reducing the
equalizer
provided
cuit. The
metrical SEPP
factor
mum output voltage. Dynamic
equalizer
input

level

lkHz).

tNHMrl

SECTION

Amplif

4-3 shows

has been achieved by using

transistor

element

in the following

output stage is a complementary

circuit.

of the

SEPP circuit

amplifier

at 0.005% distortion

Fig.

4-3 Phono

ier

basic

the

of 86dB

(2SA978)

signal source

impedance. High

is

therefore wide and overload

configuration of the

(at

at the first stage,

resistance

stage by a bootstrap cir-

The

high voltage utility

provides

is

300mV

Equalizer

Amplif

2.5mV input,

voltage

range of the

Tone Control

Fig.

4-4 shows the

circuit. This circuit is an

(HA12017P).

IC

with

Tone control

providing

by

(BASS,

the tone amplifier

basic configuration of the

NFB

type

TREBLE) is accomplished

NFB
a frequency selective characteristic.
tance
switches

to

The NFB

C7-C4 are changed

of

(by

provide

adding

another capacitors in

selection of

circuit

is changed to a

characteristic when the

the frequency.

by

the

flat frequency

TONE switch

oosition.

a ultra-low-

and

gain

sym-

a high

ier

maxi-

(rms

at

tone control

circuit with

The capaci-

TURNOVER

parallel)

in

the OFF

is

4.2 AM TUNER

The AM
tuning capacitor
tains a 1-stage RF
amplifier,

The AM
panel

decoder
minal is
(emitter-follower)

detector, and

for

is

adaptor.

the converter output

SECTION

tuner

plus

STEREO OUT terminal

connecting

section

amplifier,

The

stage.

consists

IC

an

AGC

to an

signal appearing

of a 2-ganged

(HA1197)

converter, 2-stage

circuit.

AM

passed

which con-

on the rear

stereo

at this ter-

via a buffer

broadcast

IF

Tone

Control

Section

Power
o

AmPlif
Amplifier
The

"-pilii"t

aiti*""ti"f
i.t

te2l,

;*;;
Thecurrentmirrorprovidespush-pulloperationin

stage,

this

further

and

-­in

Qf

current

voltage.

DC

in

drift
voltage

The

**g"-".rt,

ier

Circuit

circuit

basic

shown

it

amplifier

load

the

employing

which

increase

input

the

from

Q2,

Because

temperature

Q2,

is

Prevented.

pre-driver

the

arrangement

Fig'

in

comprising

circuit

NPN

an

serves

to

gain'

&cuit

prevents

and

follows

Q1

(Q4,

stage

circuit

load

The

4-5'

PNP

which

of

twin

cancel

absorbs

the

of

drift

Q5)

of

the

of

stage

-first
twin

a current

is

transis-

transistor

harmonics

even

outflow

generation

temperature

any

center

the

Darlington

a

is.

which

employs

power

is

(QB)'

base

of

of

point

constant-currentsource(Q6)resultingahighvolt-

gain.

age

"

power

Tite

spe"a

high

speea
,^*it"t

;'High

ton

circuit.
NFB

cation

bias

ing

Speea

power stage

The

arrangement,

Bicause

circuit

is

however,
""l.it,
o

active

mum
circuit

tortion

is
almost
uoitug"

these

Speed

High

operating

By

region

idle

prevents
and

circuit

This

signal

no

iut

transistors

across

disregarded.

stage

sewocontrol

bias

servocontrol

operation

Servocontrol

Bias

(Q7

tite

there

the

in

possible

down

by

Servocontrol

Bias

the

possible

1no

current,'the

the

reduces

outlined

is

applied

while

off'

the

(Q3 and

Consequently,

voltage

bias

the

in

-

Q12)

tinat

no

is

frequency

low

to

input

the

power

high

generation

loss'

heat

the

to

Q3

collector

Q4)

supplied

is

circuit'

circuit

power

provides

stage

Circuit")'

a.2-stage

is

parallel

is

stage

constant

time

region'

inputs

(DC

DC

coupling

Circuit

stage.only

cut-off).and

bias

speed

switching

of

4-6'

Fig'

in

circuit'

and

with

Q4

and

at

Q1

will

base

this

the

capacitor)'

servocontrol

When

time

power

by

The

(refer

Darling-

SEPP

in

amplifi-

will

within

with

and

Q2

on'

be

both

of

may

the

high

non-

the

mini-

there

The

stage

a

a

a

to

be

the

dis-

are

of

be

flow

may

(level

is

X

signal

signal

emitter-

by

of
be

in-

ap-

AC

Y

of

the

be

th.e

formed

X

basis

considered

resistance'

and

input

the

circuit

bias

D3

Q3,

--Witft

current,
brought

consisting

and

Q4,

and

R1

the

the

to

base

fluctuationsduetothesignal)byasimpleshiftin

level.

DC

-

"-iti"t-toffower

When

creased

;i*i-;"
it-trri,

Furthermore,

voltage

the

the

by

cirluit,

itrls

emitter_follower

of

VR1'

and

ensuring

D1

of

same

R3

with

across

positive

and

Q1

level

Q1

the

as
portion

becomel.

it

(Q1).

constart

a

point

an

on

may

emitter

points

since

junctions

PN

4

followervoltagegainispracticallyl,avoltage
moreorlessequaltothatoftheinputsignal

R5.

part of

amou"i

(by

Y

and

points

without

VER

I

OR

"easi"

Clrc,itrv

increase

the

And

base

the

power

the

applied

voltage

ttt"

positive

when

level

the

cancels

X

and

X

of

to

cutiing

the

it,

iirr"i

ir^*"J"""a

applied

age
which
il;h"
by

and
above

forms

bias

the

increased

X

the
applied.
lii"t.

o.i"ts

same

Consequently,

toii"g"'u"t"ss

current

idle

the

PRE-

d-d

t'n.

voltage

at

across

voltage

voltage

points

across

voltage

R3

collector

and

jt"g:

will

Q3

portion.

no

increase

Z't}r,ereby

Non-switching

is the

Pi"t

be

across

of

signal

1" l:]1"?:

decrease

the

maintaining

PNP

the

Y

the

X)

and

volt-

of

Q3

circuit'

excess

in
points

signal)

being

is

power

Amplifier

Y

rn

*l

||'.l

I

nl

F

is.

4-5

Power

AmPlifier

Circuit

sx-39ocl

stage

crease in current). For
signal,
ner, thereby
being cut

4.4 DISPLAY
Power

The
fluorescent
thermionic emissions from the cathode
celerated into the fluorescent substance
segmental anodes, resulting in the
This
other symbols.

An

Fig.

in
through a low-pass filter
before being applied to
(TA7318P-A).
of the non-linearity
Vd-Id
ic

range by
cuit, compressor
both left
of the signal is
a "peak held" DC

The
tube are driven by the
channel) equipped

parators.

ing
operate separately
And
the
sive segment

rises.

(noting

off

and

Q2

off.

lndicator Circuit

SX-3900

tube is used

outline of

4-7

.'lhe output

characteristics

and right channels. The

output

These

levels,

output

so each

since these comparators

power

that there actually

the negative

are operated in

Q4

preventing

CIRCUIT

output

indicator tube

the

The

20dB. The

(40dB),

thus contracted by

power

comparators are biased

light

will

the

power

indicate numerals,

to

FL

tube drive circuit is shown

circuit

compressor circuit makes

rising

of

contract

to

IC

and

voltage.

indicator

HA12010

with 12

comparator

as the input level increases.

indicator

up in tum

is a

portions

the same

power

NPN

indicators

(FL

tube).

signal is first

and a

pin

no.6

portion

contains a

peak

segments

pairs

apply the voltages

segments, each

5;6141+O---1-t!rr-f{

In

emission of light.

compressor

(4)

of the diode's

the signal dynam-

detector cir-

hold circuit for

dynamic range

6OdB to obtairr

(one

ICs

of voltage com-

will commence

as the input level

'|N++

7r7

stage from

this tube,

letters

of the

of the

at increas-

tm

slight

of

man-

feature

are

of the

passed
circuit

for

succes-

LPF

de­the

ac-

and

IC

use

FL

each

to

to

Frequency

Frequencies

played
tube
ments
from

Display

received by

in digital form by fluorescent

(FL

tube).

(a - g) (see

0 to

9

Each

digit employs up

Fig.

4-8) to display

(with

the exception of the left hand

digit which employs only 2

o

F

Fig.4-8

The

signal source
tion is the local
buffer

(M54451P)
sion
applied
This IC

7-segment
on according to

amplifier

where it is

(1/8

for AM

to the frequency

is responsible

5-digit display

AM LOCAL

AL

OSC,S I GN

FM LOCAL

IG NA L

OSC,S

FM-AM

Fig.

(fA7318P-At

tc

7-Segment Digit Display

during both AM

oscillator. The

(FET)

subjected to frequency

and 1/80 for FM)

for

time-shared

(M54451P)

rc

SELECTION

SIGNAL

4-9 Frequency

1/2

SX-3900

the

indicator

to

all numerals

segments b and c).

FM

and

signal is

to the

counter

the dynamic drive

(each

digit being tumed

sequential

(P05009)

rc

FL

Display

passed

prescalar

before

IC

scanning).

TUBE

Circuit

(PD5009).

are dis-

7 seg-

recep-

via

a

IC

divi-

being

of the

fltl E- -fl

I

w(8rl

)

I

o.oo1

tc ( HAi2oro

--

--

tll

O.O1

FL

TUEE

Fig.4-7 Power

)

trn

Dtr !! !I

O.1

1

Indicator Circuit

EE trn

10

Dt]

pO

outline

An

given in

FL

nected

;i;"dr
G;J""i

being

nacf,"
tul.
terminal.

;00u;
L Ievel
tube

block

-

a

tube

parallel,

in

(rel

grid ior
up

Iit

aigit

Pin"no.?

The

for

signals,

brightness

"Note

is

H

perioa).

driven

is

iune

be

rrruy

,r"rr

ZUHz

f.f

ffre

signal

basic
aiuirlon.-p.tlse
control

signal.

--

FROM
PR ESCAL

the

of

diagram

g

segments

the

4-11)

nig.

each

succession

in

for

up

lit

PD500g

of

time

input

level

therety

(by varying

that

static

by

varied

by

crystal

in

used

signal

F ig.

A R

composition

in

form

(anode)

-

D5

D1

applied

digit)

result

from

during

1ms

the

is

division

pulse

signals,

varying

the

the

since

the

drive,

changing

oscillator

preparation

the

the

and

Signal

isit

D

1

4-1

NESS

IGHT

R

B

LECTION

SE

GNO

Vcc

Fio.4-10

PD5009

of
4-10'

Fig'

each

for

division

time

grid

each

to

in

left

the

each

brightness

width

to

and

degree

the

segment

power

indicator

degree

grid voltage'

the

generates

of

counter

gate circuit

D5

coNTROL

GATE

DECI

COUNTER

Block

With

digit

pulse

(inde-

digits
.the
hand

5ms

selector

set

is

200ps

of

lighting

bright-

of

the

03

D4

DRIVER

DIGIT

CIRCUITLATCH

M AL

Diagram

is

the

con-

side'

inter-

to

for

FL

FL

the

time

MULTIPLEXER

LOAD

5'DIGI'T

COUNTER

ROM

16

x

(pin

54

mode'

the

in

the

-rri"
coping

in
stage,
acc-ording

SX-3900

locking

of

10kHz

lntermediate

10.67MH2
'10.70MH2

10.73MH2

nos'3

The

SX-3900

combination

different

s

witir
and

53

to

FM

any

(digit

digit

f

requencY

-

6)^are
reception

2

Table

(see

of

during

IFs

offset

]f

being

54

ceramic

the

stage

quartz-lock

frequency

the

in

used

1)

in
preset

within

second

Counter

of

Table

lC

1

Terminals
d"i;;;tt";
;;d"t

emptoved

;;;;;;J

;;;i;

iH

)re

;.;;

ceramic

IF

arrring
characteristics.

"^'Aftfto.,gft

.Vrt"­;ir;FM

PRESETAALE

DECIMAL

22-BlT

(PD5009)

S1

reception

varving

bv

l;'

uni

required

filter

mode

FM

the

"capable

is

the

bani,

-

decimalplace)intheFMfrequencydisplaywill

0'

or

5

as

appear

.*htu

ttre
though

ur"
",ritr,

liilit"
;;J",

indicatorsinthelrequencydisplaysectionarelit

according
MHz

onlY
fr"qrrerr"y

iUNf-fqC

segments

the

tf,"

driven

grid

,iuti"

pu"lse

djnamic

to

indicators

display

^SiCXaL

ana

uy
driven

is

timing,

a'iul'

OS

the

lit

are

tube-also

FL

inclicators'

(anode)

itre

for

corresponding

according

thereby

placing

ttt addition'

timing'

while

according

incorporates

these

to

the

the

the

the

to

And

indicators

drive

D3

the

segments

and

AM

kHz

timing'

D1

in

are

input

FM

the

filter

al-

cir-

time

FM
and

sx-39ocl

TUNING

The TUNING
tuning
casting station
2 detuning
direction
from.
lined in

The
station
center
on and
differential
off and
signal

(PA3007-A)
(Q17

more than

The DC voltage on
describes

particular

a
pin

voltage is amplified

(Q19
tor switch

When

quency

higher frequency), the

a
be higher than that

voltage will thus be

tor
on,
detuning
When,
quency
(or
pin
being tumed on to
(left
either

high, resulting in

be
turned off, which means
indicator will not be lit up.

Once

properly,

equal.
turned
ing direction

And

creased

the center tuning

C77 is charged

turned

indicator

lndicator Circuit

indicator

indicator

in wnich

The corresponding

Fig.4-72.
TUNING indicator
has

frequency.

Q21

Q24

appearing at

&

Q18)

t100kHz.

an S curve when

no.2 serving as the

&

Q20)

circuit

tuning

side

voltage raised,

and the

direction

on the

is approached

when tuning away

no.4 voltage

hand

side) detuning

Q22

the broadcasting

the voltages on

Consequently,

off, which

since

base voltage,

on, thereby

LED.

(which lights up when

frequency

direction

been tuned to

turned

amplifier

being turned

and

when

broadcasting

and

(or

higher frequency

or

Q23

indicators

Q24

indicators which

the station

This is because

off

[Q19

pin

passed

the station

by the differential

then applied

(Q22

frequency

to a

tuning away

on

lowered and the

resulting

indicator also being turned on.

other

up via

hand,

from the

will

light up the

is on, the

Q24

means

is

turned

Q25

indicator

R99, resulting

lighting

no.13

&

pin

to a lower

be lower, resulting

Q22

consists

properly

is

has been

drive

is activated

within

(resulting

&

Q20]

on) by the

of the

via the

pin

no.4 of

tuning to and
frequency, the voltage on
reference

to a

Q23).

from the

voltage

no.2.

in

the

direction

Q24

being tumed

that the center tuning

frequency

pin

and

that neither

will be on

because

off
will

light

up the

of a center

a broad-

tuned) and

indicate the

tuned away

circuits are out-

once the

t100kHz

Q16

in the detector

being turned

IF

Schmitt circuit

is tuned away by

level.

polarity

from

frequency to

pin

on

The

Q20

being turned

Q23

(right

broadcasting

low frequency

frequency)

lower frequency

indicator. Wherl

base voltage will

has been

nos.2 & 4 will be

will both be

Q23

of the

in this

be turned

Furthermore,

up.

in

Quartz

of the

is turned

FM

muting

system

PA3007-A

away from

This

amplifier

detec-

high fre-

the

no.4 will

collector

collec-

Q19

hand side)

in

on and

tuned

detun-

of the de-

on, and

being

Q26

Locked

DC

fre-

side

the

Q22

Q25

case.

IC

SCHl,llTT
C IRCUIT

Fig.4-12

SIGNAL

The

FL

Indicator Circuit

SX-3900 SIGNAL indicator consists of an

tube 5-point indicator display.

drive signal obtained

(PA3007-A)

Tuning Indicator

from the

and AM tuner

FM IF

(HA1197)

IC

amplified and then applied to the

(HA12010).

IC

comparators similar to those
power

indicator circuit, 5 of these

to drive the SIGNAL indicator

PROTECTION CIRCUIT

4.5
purpose

The
speakers
output
the

1.

2. Upon

and the

circuit

following

cases:

During the

power

supply

detection of

circuit,

caused by

IC

This

contains 12

(Fig.

this

of

power

circuit

is to

amplifiers.

is automatically

"transient

is tumed

operations"

on and off.

DC voltage

a
component

employed in the

opened

dent.

an overload,

Upon detection

3.
circuit

short

Muting Operation

of

in the load.

Power

when

Supply

On and Off

With reference

is

supply

turned on,

time constant

If

there is no

be

off,

through

conducts, the

Q6

input

and the timing

R8

and

muting on the

When the

power

Fig, 4-74

to

Q5

of the

-B

(DC)

R7, and

relay operates,

power

amplifier

supply

turns

on

capacitor

thus

when the

off

circuit

and

Q3

Q6

will be

is turned off,

Circuit

The

signal

meter

system

is first

indicator drive

pairs

of voltage

pairs

-13).

protect

The relay

being

both the

used

in the

in any of
when

the

in the output

failure or acci-

caused

is

by a

Turned

power

-B

due to

(The

is very small.).

they will

Q4,

C4 charges

turns on.

When

and the output

removed.

-B

will

IC

up

(

HA12010

lc

)

abruptly
residui
rapidly

upon
restore

DC

ter
Any
the
emitter

turns
is
As
will
circuit

decay,

component

discharge,

the

muting.

Voltage

output

The

and

DC

qa

voltages

power amplifier,

and

C4 will

on.

negative,

consequence,

become

oPen.

to

and

Q5

of

will

Q6

relay

will

Detector

via

is

a

circuit

trase

appearing

it
If

base.

Q4

rapidly

QB

Q6

will

on'

tums

de-energized,

conduct

will

+B.

As

to

cease

become

connected

low-pass

the

be

will

voltage

the

discharge'

will

C4

turn

causing

thus

Fig. 4-13

owing

result,

a

conduct,

to

C4

where-

de-energized

the

to

filter

output

applied

rapidly

off

(R5, C2)'

circuit

to

positive,

is

If the

discharge'

the

and

the

Q3

the
voltage

output

Signal

the

will
and

emit-

of

Q3
Q4

relay

Indicator

Overload

The

load

Fig.
tra'nsistor
corners

become
scribed
discharge.

relay

the

output

the

Circuit

Detection

overload

(RL) in

4-15).

(Q2) are

ttre

of

forward

value,

As

will

circuit

one

The

detector

side

base

of

and

circuit

a

connected

if

bridge,

Q2

so

biased.

will

If RL

turn

consequence, Q6

become

4-15

Fig.

de-energized,

oPen.

to

Overload

incorporates

Wheatstone

emitter

RL

on'

of

the

to

decreases,

below

falls

will

C4

tum

will

thus

Detector

bridge

sensing

a

opposite

Q2

a

rapidly

off

causing

the

(see

will

pre-

and

Fiq.

4-14

Protection

Circuit

DISASSEMBLY

5.

sx-39ocl

Wooden

Remove

wooden

the

Bottom

Remove

bottom

Cover

the two screws

cover.

Plate

the thirteen screws Q to detach the

plate.

panel

Front

(O

o.r each

S

side of

Front

Panel

Remove
two screws
Remove

the two nuts @ from

all the knobs

from

@

the top edge of the front

'-

.tt

\--

'-=.::att/7

\ )rt"

pulling.

by

the control

\

7

liemove

panel.

shafts.

the

4.6

SURGE CURRENT SUPPRESSOR

Since
power
in

the
current
reach several hundred
suppressor circuit used to reduce this sudden
surge is

When the

supply of

open.

the sudden surge

thereby
When the output DC voltage
circuit
close,
required for
shorter
circuit

the SX-3900 employs a large toroidal

transformer and two 15,0009F capacitors

power

shown

But

reaches a certain

and R1 consequently be by-passed. The time

to operate when the

supply circuit, the sudden surge of

when the

AC

when this switch

greatly

than the time

power

Fig. 4-16.

in

POWER

power),

of
reducing the flow of current.

this to occur, however, is considerably

supply

amperes.

switch

the relay contact

current is

prescribed

required for

is

The

(S1)

(S1)

passed

of the

power

turned on

surge

is OFF

is tumed

through R1-,

power

level,

the

supply

current

(i.e.

(S2)

supply

52 will

muting

is

tumed

may

no

ON,

is

on,

so there is no undue

tion

of the receiver.

Microtemp
coupled
abnormality in
the heat
below,

When
the relay driving
52

thereby

and

the

Fig.4-16

to R1.

generated

POWER

the

primary

Bottom

is

If

the

opening the

circuit is

Surge

plate

effect upon normal

a temperature-sensitive

52 fails

power

in R1 will cause Microtemp

switch

circuit.

Current Suppressor

to close

supply
primary

opened, thereby

RELAY

circuit

circuit.

(S1)

is tumed OFF,

Circuit

opera-

due

or relay,

opening

fuse

to an

to