Pioneer SX-1250 Service manual

AM

/FTA

STEREO RECEIVER

sx-1e50

MODEL SX.125O

COMES

IN

THREE VERSIONS DISTINGUISHED

AS FOLLOWS:

Type Voltage

KCU

HG

120V only CSA

22OV and 24OV

(Switchable)

s 1IOV, 12OV,22OV

When repairing

1.

SPECIFICATIONS

2.

FRONT PANEL

3.

CONNECTION

4.

CIFCUIT DESCRIPTIONS

4,1

4.2

4.3 Protection

4.4 Power

S or HG type,

DIAGRAM

Tuner Section Audio

Section

Circuit

Supply

FACILITIES

please

.

Circuit

and 240V

see

{Switchable)

the

manual on

CONTENTS

Remarks

UL

{Canada}

with de'emphasis

SEMKO DEMKO

General export model with de-emphasis selector switch

page

101.

and

{U.S.A)

selector switch

{Sweden),

(Denmark)

{25pslsops/75psl

NEMKO

and

(Norwav),

(Finland)

El

.......,. 17

approved

(25psl75ps)

approv€d

4 6 I

11 14

....... 18

5.

LEVEL

6.

BLOCK DfAGRAM

7.

DlsAssEMBLY.

8.

PARTS

8.1 Front

4.2

8.3

8.4

8.5

9.

ADJUSTMENTS

9.1

9.2

9.3 Power

9.4

10.

DIALCORDSTRINGING

11.

EXPLODED

12.

SCHEMATIC DIAGRAMS, PARTS

12.1

DIAGRAM

LOCATION

Panel

View . .

Rear Panel

View Top View Bottom Front

View

AM Tuner

FM

Tuner

Amplifier

Stabilizer

VIEWS

LISTS

Miscellaneous-parts

.,..

. .. .

.

P.C.

BOARD PATTERNS

AND

.... .. ... 19

....... 20

........22

........ 25

.........,27

........29

.....,

.......33

...........36

...........38

... .. . ....

........

31

. .. .

3b

38 39

... . 40

51

I

i

I

'--

\o

12.2

12.3

12.4

12.5

12.6

12.7

12.8

12.9

12.10

12.11

12.12

12.13

12.14

12.15

12.16

12.17

12.18

Schematic Diagram

Internal The Tuner De+mphasis

Equalizer

Function

Flat Amplifier 5P Connector Control Amplif ier

Filter Microphone Pourer

Speakers Protection Stabilizer Power

Circuitry of Integrated

Circuit of

Assembly

Amplif

Amplif ier

Supply

FM Front End

(AWE-0681

Switch

Amplifier

Switch Assembly

Assembly

ier Assembly

Jack

Assembly

Switch Assembly

Circuit Assembly

Assembly

Assembty

Assembly

(AWS-094)

(AWG-042)

(AWX-062)

Assembly

(AWM-089)

(AWX-@71

(AWH-048)

(AWS-G}S)

(AWR-l

(AWR-I07)

Circuits

(AWB-023)

(AWX-099)

(AWF-021

(AWG-0411

(AWM-091)

06)

sx-1

25C,

s3

55 56 57

63

)

64 68 70 75 76 80 83 84 88 90 93 96

I

13.

PACKING

14.

PARTS

15.

SUPPLEMENTS

15.1

15.2

15.3

15.4

15.5

15.6 Poriver

Contrast Schematic Schematic Diagram De-emphasis

Speakers

LIST

EXPLODED

OF

FOR

SX-l250/HG

of Miscellaneous-parts

Diagram for

Switch Assembly

Supply Assembly

SX-1250/S

forSX-l2sOlHG.

(AWR-108,

VIEWS

(AWS.098,

.

AND SX-1250/5

..

(AWX-101,

for

S

for

HG type)

type)

..

........101

.....lO3

..... lOb

.....1O7

........

.........110

98 99

108

a

!

1. SPECIFICATIONS

Semiconductors

FETS....

|Cs.....

Transistors

Diodes Power Amplif ier Section C.ontinuous

Total

Intermodulation

Frequency Response Input Sensitivity/

Output

Damping Factor

Hum and Noise

Preamplif

Input Sensitivity/

PHONO Overload

Output Level/l

..

20 Hertz

Power Output

(Both

channels

Harmonic Distortion

AUX) Continuous Rated 80

watts

output,

per

watt

1

output,8 ohms . . . No more than

from

AUX)

Continuous

watt!

80

output,8

per

1 watt

output, S ohms

POWER

driven). .

per

channel

8 ohms . . . No more than 0.05%

channel

Distortion

Rated Power

per

channel ohms

channel

|

mpedan

|N.........

Ar\4P

Speaker.. Headphone

(20H2

20,000H2,8

to

(lHF,

from

watts

160 200 watts

(20

Hertz to

Power Output. . . No more than 0.1%

power

(50

Hertz : 7,000 Hertz = 4: l,

Output. .

power

. . .

power

. . No more

. .. ...

short-;ircuited,

. . .5H2to

ce

ohms) .

.......1V/50kohms

.

A,

......

to 20,000

per

channel

Per

20,000 Hertz,

. No more than

No more than

100,000H2ildB

B, C, A+8,

Low lmpedance

A Network)

ier Section

lmped ance PHONO I PHONO

2

t\4tc....

AUX,..,

TAPEPLAYI.....,

TAPLPLAY2......

(DlN

TAPE PLAY

PHONO PHONO

I

2

conne(lor). (T.H.D.

Level

0.1%)

. 2.5mV/50k

2.5mV/50k ohms

. . 6.5mV/50k .

1 50mV/50k . 1 50mV/50k . I 50mv/50k

.

. 150mV/50k

. .

500mV

. .

s00mV

mpedance

REC I ...,.

TAPL

,

TAPERLC2......

TAPE

REC 2

(DlN

connector)

........150mV

.

. .

30mV/80k

......

......6

......82

......60

Hertz

(8

ohms)

(4

ohms)

from

O.O7%

0 1%

0.05%

than

0.O1%

B+C, A+C

.......30

. .100d8

ohms

ohms ohms ohms

ohms ohms

(1

kHz)

(1kHz)

ohms

5

PRE

OUT

Total lllrmonic

(20Hr

Frcquency

PHONO

AUX,TAPE

Tone Control

BASS...

I'REBLE

Filter

LOW....

HIGH

Loudness

at 40dB

Hum

and Noise

Distortion

ot 20,000Hr,

Rcsponse

IAA equ,rlizrrion).

{R

PLAY

.

,..

Contour

position)

I V

.......

(Volume

. . . . .+6dB

(lHF,

short,circuited,

ourpur)

.30}12

. . [4AlN

. .

control

. . No more

tOHzto50,000H.,lldB

SUB l\4AlN 1'l0dB

SUB

set (100H2), +3dB

power)

PHONO........

AUX,

l\4uting

TAPE

..

PLAY

FM Section Usable

Sensitivity. . . l\40No

Usable

Sensitivity

50dB

Quieting

Signal-to-Noise

Sensitivity ....

Ratio at65dBf . .

STEREO..

(lHF'58)

l\40No . . STEREO..

..

l

.....

11.sdBf

.

36.0dBf

MONO.......

STEREO.....

Distortion

at 65dBf l00Hz.....

i\40No......

STEREO....

l kHz . . . . . .

MONO... . ..

STEREO....

.

6kHz

.. . l\40No . ......

STEREO .

Frequency

Capture AlternatcChannelSelectivity Spurious

lmage lF

Response AM Suppression /VlutingThreshold Stereo SubcarrierProductRatio SCA Rejection Antenna Input

Response

Ratio

Response

Rcsponse

Separation

Ratio ...

Ratio

...

Ratio ...

. .

Ratio ...

...

50dB

. .

30Hz to l5,000Hri?

.....13dBf(4.9pvl3004)

(lkHz),

35dB

lV/1k

ohms

than O.02%

ro 15,000H2 r0.2dB

1l0dB

(l00Hz)

t

sdB(s0Hz)

(tokHz)

t

(20kHz)

5dB

30Hz

Network,

A

(12dB/oct.) (12dB/oct.)

(t

okHz)

rated

.. . . 8 kHz

... 75dB ...90dB . . 20dB

8.7dBf a.sdBf

(3.orv/300s}) (s.8gV/300[l)

. . 1.5irV

(a.1pV/3000)

(69sV/300())

80dB 7 4dB

0.1%

.

0.25% .0.1% .

0.2/o

0.3%

. . .

.

O.3Vo

3dB

..........l.OdB

........ 83dB

.......11OdB

.........110d8

...120d8

.........60d8

(30H2-t5kHz)

..........

..........74d8

300 ohms

75

ohms unbalanced

14dB

balanced

F

I

.

I I

s

I

A\,?

AM Section

Scnsitivity

Sclcctivity Signal-to-Noise

lmage

lF Rcsponse Antenna

l\4iscellaneous Power Rcquircmcnts

Powcr

Dimensions........

Weight

Furn Fl\4

T-typc

Opcrating

Hex.

(lHF,

Ferritc antenna)

(lll

F, Ext. antenna)

........

Ratio

Rcsponse

. .

Consumption

Without

With Package ..... 33.2kg

ished

Wrench

Ratio .......

Ratio . . .

21-7l8(w)

Packag€

Parts

Antcnnd

Instructions

. .

.

Built'in Fcrrite

556(W) x 186.5(H)

......300pV/m

......... l5irv

.........40d8

.........55d8

.........65dB

.........85dB

Loopstick

... 120V

.......6s0w(uL,csA)

x 7.3/8(H)

.

. 29.2kg(641b

Antenna

'1200W

x464.5(D)

x 181/4(D)

(73

lb 1 oz)

60HZ

(max.)

mm

in

4 oz)

.1 ,1 .t

six-1

Elscl

s

NOTE: Specifications tion

uithout

HEX The accessory Hex. wrench is

VOLUME

setscrew in

If required, loosen the setscrew

into the wrench scratch

ond the desigtr

notice due

WRENCH

and TUNING knobs, or for tightening

the event it becomes loose.

hole on the side of the knob

counterclockwise.

panel

front

the

subject

to

improuements.

provided

particularly

Be

when employing

possible

to

by inserting the wrench

modifica.

for removing the

its

and tuming the

careful not to

wrench.

the

5

2.

FRONT PANEL FACILITIES

F

FUNCTION

To

select the

NOTE: Only one FUNCTION ttme.

AM

FM

TAPE

DUPLICATE

thi5

Set or edit a recorded

SELECTOR

program

......... For

. . . .

switch in the

BUTTONS

source,

push

each button as

button should be depresaed

AM broadcastreception.

o

For FlVl receives phonic

liihts up when

tape using two tape

stereo reception.

monophonically during

broadcasts. Th0

lhe br"J,lL.r.t r\ n

SWITCH

(down) position

ON

o

Automatically

5TE

REO indic.rror

to

decks.

follows:

ot o

o

FlVl mono-

\lcrcu.

duplicate

PHONO 1 .....

AUX

........

A

\-' o

PHONO

2/MtC.

To operate a turntable PHONO 1 input

listening

For tridge tape connected

above for PHONO 2

As

reproduction nected

panel. connected to the connected to the De useo.

to the Mlc

Note, when

jacks.

to

audio

player,

to the AUX

TV sound

through

iack

PHONO2

the

connected

component

input

microphones con-

is on the front

microphone

the turntable

to the

tuner, etc.) jacks.

or for

iacks,

cannot

iacks

(car-

is

.-.

I

rt

I

TAPE

MONTTOR

these switch in the ON

Set 1

2

For

With a taDe deck connected to

.. ..

jacks monitoring of a recording

sible. Same as in 1

..

to the

normal use, leave

(1,

(REC

TAPE 2

VOLIJME CONTROL SWITCH

The extremely

be finely controlled by combining the cali-

can brated

ING switch. The AUDIO briefly lower

taDes.

VOLUME

high

MUTING

the

s?F$

2)

SWTTCHES

(down) position

and PLAY),

above, with a tape deck

jacks

(REC

and PLAY).

in

the OFF

(up) positions.

AND AUDIO MUTING

power

control and

volume when changing records or

output

switch

as follow:

are

I

pos-

the TAPE

either

in

playback or

progre5s

connected

of the SX-1250

the AUDIO MUT-

can also be used to

ADAPTOR

When equalizer adaptor, depress this

SWITCH

employing

ADAPTOR

adaptor components,

processor,

RG

switch to ON.

or Dolby NR adaptor,

r

VOL!ME

such as a

graphic

I

t

v

i

Y

I

I i

i

I

t

I

'

I

t

I

i

I

SPEAKER BUTTONS

sets of speaker

Three on the rear selected by depressing

A ...........

B

...........

C

,..........

NO?ESr

1. Whetr any two preaeed

speaker systems

depressed.

2. For

panel,

simultaneously,

possible

is not the same time, euen

priuote

the

SPEAKERS

Dosition.

terminals, A,

and the required speaker

the SPEAKERS Speaker Speaker systems Speaker systems

buttons

will come

to

operote

listening

buttons

B, and C, are

systems

buttons

systemsAoperate

B operate Coperate

(A+8,

B+C,

the eorresponding

into

operation.

three

all

though all the buttons

through heodphones,

to the OFF

speaher

as follows:

C+A) ore de'

Howeuer,

systems

(undepressed)

provided

can be

pairs

of

ot

ore

return all

FM TUNING

With the SIGNAL make fine adiustment meter

SIGNAL

For AN4

Al\4

FM tuning:

it

SPEAKER

METER

meter needle deflected

by

(indicating

needle

optimum

METER

and

Flvl station

tuning:

Tune SIGNAL

for

meter needle

the

Both work SIGNAL tuning. Then

SIGNAL and

together. The optimum

meter

SYSTEM INDICATOR

FM STEREO

to

centering

tunings.

maximum deflection

needle

use the

the FM

reception).

right.

to the

FM TUN ING

the same as

is

Fl\4 TUNING

INDICATOR

the right,

TUN

of

point

rn€ters.

ING

the

meters

the

of in

AM

TUN

Sele, obse

stGl

Ft\4 |

Lear

supF tw€{ supF oepr

PHONES

Accepts stereo

WARNING: Do not

domage the microphone.

'ACK

headphones.

plug

a

microphone into

the PHONES

POWER SWITCH

After turning

8

seconds, during which time the

operates

this

switch ON

to

eliminate unpleasant norse.

there is a

TWIN BASS CONTROLS

Adiust low frequency tone. 100H2: Adiusts frequency band below

effectiveness

50Hz: Provides

band below

r5dB.

is

50Hz

at

100H2

additional control for the frequency

200H2. Control

r10dB.

is

TONE SWITCH

In the OFF section less of the

to operate with a flat frequency response regard'

tone control

(up) position,

this

setting.

switch

jach

os may

delay of

protection

causes the amplifier

some 6 to

circuit

400H2. Control

effectiveness

at

LOW CUT

when low-oitched source) is obstrusive

l2dBloctave, attenuation no interference is experienced, release

HIGH CUT

When

other source) is unpleasant, depress

12dB/octave attenuation at frequencies

there is no interference, release this button.

(30H2)

(8kHz)

high frequency

FILTER BUTTON

rumble {from

depress this button

FILTER

scratch noise

turntable

at

frequencies

BUTTON

(from this button to

this button.

motor or other

provide

to

below 30H2.

worn records

provide

above 8kHz.

or

FM

Whr

oepl

lf

the tnts

TWI

Adi

lf

10k 20k

right,

of

I

t.

meters

G nt of

in

as

m€Iers.

the

AM

TUNING KNOB

Select the observing SICNAL and

FM MUTING

Leave this suppress unpleasant interstation tween suppressed depress this

station

the SIGNAL meter

and tune for optimum reception

TUNING meters

BUTTON

button undepressed

F l\4 stations.

by this function,

button to the

Low-strength signals

PROGRAM

for FM stations.

so

OFF

SOURCE

for AlVl

(in

the ON

noise

pick

to

position.

stations,

while tuning

up a weak station

and

both

position)

be-

may also be

INDICATOR

by

to

six-1

e50

TOR

or other

provide

lOHz.

lf

rcords

or

,provide 3kHz. lf

o 6ru'"-6*6

FM MULTIPATH BUTTON

When

selecting depress this button sothat multipath noise is heard the speaker

this button.

TWIN

TREELE CONTROLS

Adjusts high frequency tone.

1okHz: Adjusts frequency

effectiveness

20kHz:

Provides additional control for band 20kHz is

the

systems. To listen

above

r5d

position

best

to

band above 2.5kHz.

at lokHz is

5kHz.

B.

Control effectiveness

for the Fl\4 antenna,

FN,l broadcasts,

r10dB.

the frequency

from

release

Control

at

MIC

JACKS

For connect each channel microphone5.

NOTE:

Use the hEh impedance

phone plugs.

(L

and R)

jack5

(oboue

VOLUME CONTROL

Adjusts Scale with the MUTING switch, finer tion can be

6.

output

is

AUDIO MUTING

Depress this

20dB.

This VOLUME ph

on e.

level to

graduated

performed.

speakers

in

dB, and

See additional description

SWITCH

switch to attenuate the audio output by

convenient

control, for

feature saves having to disturb the

example

LOU DN ESS SWITCH

Depress frequency the listening pensates treble.

this switch when listening

response of

volume, and the depressed

for hearing response by

the human ear varies according

IIIODE SWITCH

For stereo

depress

for MONO will be mixed speaker systems.

BALANCE

Adjusts left and right speaker

playback,

to release, if already depressed).

playback,

to

CONTROL

the

balance

leave this switch

and right channel

left

produce

monophonic sound

between

systems or headphones.

the left

and headphones.

when used in conjunction

and

and right channel

20ks7) with 6mm diatn.

wider range

attenua-

page

on

_2OdB

when answering the tele-

at low

emphasizing the bass

the sound

volume. The

position

undepressed

When depressed

stereo signals

volume from the

com-

and

from both

to

(or

3. CONNECTION DIAGRAM

TURNTAELE

OUTDOOR

FM ANTENNA

TURNTABL E

TAPE I

T.TYPE

FM ANTENNA

FM

OE.EMPHASIS

Normally, "25ps"

ernphasis; 25rrsec.l

nected

*

The word

set this swatch

when

only

berween

"Dolby"

teeder

3O0A

ffi-[]

SWITCH

listening

with a Oolby'

the ADAPTOR OUT and ADAPTOR lN

i! a trademark of Dolby

to

"75!s".

to an

system

Be sure

F[,

to

broadcast

NR adaptor con-

Laboratories

set

ir to (pre-

Inlj.

4.V

GND

RIGHT

SPEAK

ER

SYSTEMS A

LEFT

RIGH'

IAPE

(open{eel,

OECK

casselre}

LINE LINE INPUT OUIPUT

EE

irulr(il

-00

r0r

ftrovt ScRtyis

yr

LINE INPU-T

rtr

30r

0T ct

LINE OUTPUT

DOLBY

NR ADAPTOR

Itl:i.i+l

LINE LINE INPUT

OUTPUT

PR€/POWE The

bridg€ connecting

POWER normal

us€. ll rhey

sound

will

swatch

off

'

rl

R AMP

lN

iacks

come from

the

should

are

power

4 CHANN EL

FM

ADAPTOR

ose

.

plugs

beiween

always

disconnected

the

supply before

be

speakers. Atways

DISCRETE

I e0

pRE

teft

OUT and

position

in

or removed,

be

artempring

in

no

sure to

to

RIGHT

SPEAKER

t-t t-t t-l

t=J t=J u

LEFT

SYSTEMS

CONVENIENCE

lr tP

RIGHT

8

SPEAKER

SYSTEMS C

Unswitchod:

max.) not

l2O0W

Switchsd:

(sow

max.l

OUTLETS

frequentty

Less

require

into

either ot

frequ€ntly

A

deck.

elc.) can By leaving nent

in

the ON componenr switch

operation.

used

coupled

these outlets.

used

component

plugged

be

power

the

position,

wi

be coupled

components,

power,

can be

(turntabte,

into

switch of

povver

with

rhat compo,

suppty

the sx_1250

which

do

ptugged

tape

this outlet.

ro the

v

\f

4.

CIRCUIT

4.1 TUNER FM Front

The

FM front employing amplifier FETs, and a local lent

of a cascode

grounding allowing The

output signal

gate-1 oscillator technique oscillator,

if the

A variation

oscillator. local load,

form.

eliminated.

of the

received

oscillator eliminating

Drawing effect

SECTION

End

end is composed

a

5-gang variable

and

mixer employing

gate-2

stable

RF amplification

mixer stage MOS

output signal

minimizes input

resulting in low

signal input level

of a

Inclusion

DESCRIPTIONS

oscillator

amplifier

of

the dual

of the

Clapp circuit

of a buffer

and

mixer reduces

distortion

of the local

of a tuning

capacitor,

with buffer.

is

amplifier

RF

FET,

is applied

power

mutual interference

is high.

of the

a

2-stage

gate

dual

An equiva-

produced

gate

MOS

at high

amplifier

gain.

is applied

while the loca.l

gate-2.

to

ftom the local

forms the local

local

oscillator

oscillation

oscillator is

circuit

RF

MOS

by

AC

FET,

to

This

even

between

wave-

also

FM lF

Four integrated ceramic (diagram

a constant

current-limiting

55) tor, circuit

SX-1250 taken ftom applied differential output

Section

filters

page

on

current

contains IF

meter drive

contained

however,

the stage

to

TA7061AP. This latter

amplifier

goes

to

circuits

compose

limiter.

limiter

and

the ratio

(ICs)

56) is

a differential

source

HA1137 (diagram

amplifier,

muting circuits.

within this IC

and instead

prior

(diagam

detector

and

this

and

to

on

Etx-1

four dual

section.

amplifier

functions

quadrature

The

is not

the

for FM

used in the

the IF

detector and

IC is

a 3-stage

page

56) and its detection.

ElEiCt

element

HA1201

with as a

page

on

detec-

detector signal is

15 !rut8at.

100 0 0 ..

t-

L

Fig.

L Circuitry

of

Flvl

tront

end

Fig. 2. Block diagram

for HA1137

Multiplex Decoder

The multiplex employs shown

in Fig. 3

1. Switching A PLL 76kHz

is

oscillator:

controlled

decoder

an IC

Signal Generator

(phase

generated

an oscillator

by a voltage)

by a frequency

(HA1196)

(see page

locked

contains three

with

55 for circuit).

loop) system

the

by

VCO

in which

and converted

divider, then become 19kHz. This signal component applied between them feedback the oscillator

loop is termed PLL and

This

signal

employed as

and

(19kHz)

phase

to a

comparator

is converted

this voltage

sig4al is

synchronized

a switching

2. Automatic stereo

With

the PLL

locked to the

signal and a 19kHz

produced. comparator that amplitude. As switch

A voltage

is

it increases, the

becomes on. The

proportional

the

of

is applied to the VCO.

locked to the

to the

detector

signal is then obtained at

switching signal

to the demodulator.

sections and

a block

(voltage

diagram

is

employed.

controlled

frequency

into 38kHz

divided

and the

detected

again to

stereo

signal

where the difference

into a voltage.

pilot

a 38kHz

pilot

signal

switching

is

obtained

signal.

pilot

sig.nal, the

the same

of

phase the

to the

pilot

lamp lights and

is applied

as

is

pilot

are

By

And

signal.

pilot

are

phase signal

the

However, pin

(grounded).

demodulator

tion

if the FM muting

12, the detector

Therefore

supplied and mono

is

obtained.

is not

3. Demodulator Two differential switching circuit applied nately

to the

switched ON and OFF

amplifiers

(Fig.

base

of

signal. The composite demodulated and

Q3

and R3.

R2

its low level composite

and

modulated modulated at the collectors of Adequate

low distorbion. However,

for is raised, the voltage is reduced and voltage

by the switching

loosely coupled at their

are

is driven

Q6

by switching signals in opposite

Q1

current flow

range available

clipping occurs

is limited by IC voltage

this reason, current

inserted and removed

at

I2 in Fig.

at the emitters of I3 and 14 in Fig. with adequate remarkably the demodulated

and

Q3

Q6

4. The same amount of

4.

current and distortion

reduced. A

signal

is also applied

signal

circuit becomes

a switching

signal

are employed

4). The Q3. Q1

composite signal

and

Q2

by the

signal amplified

of

Q1

emitters

in

opposite

signal output

of

and

Q2,

is required

and

Q4

phase

are

cancelling crosstalk.

in

base bias voltage

if the

at the

(power

requirement).

from an external

collectors and

and

Q3

and

Q3

Q6

therefore operate

in this stage

feedback amplifier

produce

to

the IC outputs.

disabled

reproduc-

are alter-

switching

at

and

Q2. Q6

phase

The de-

Q5.

combined

and

Q3

collector

source

become

curlent

become

to

amplifies

to

to the

in a

Q3

by

R1,

to

Q3

is de-

Q6

supply

For

is

11

is

Conposilo

irgral

I

I I

oulpur Fig.3.

I'lrt ing

sip,l

Block diagram

lor

HAl 196

Y

Ai0

Fig. 4.

FM Muting Circuit

DC voltage emetges

event of more than

the input level sion). This is employed circuit to

perform

Basic circuitry of demodulator

(Fig.

from

(less

4.9pV antenna

than

muting by the reed relay.

5) pin

12 of

l7OkHz

for shorting the

(HA1137)

IC

detuning

input conver-

AF

in

or low output

Multipath Monitor

When signal,

(amplitude forms. is sound amount) of multipath

Short term level taken as drive terminal MULTIPATH this signal fier and can conditions

multipath

the signal

Since

fixed,

by converting

and listening

a signal from

modulation

becomes connected of multipath

Circuit

reflections

is converted

the amplitude

variations

(pin

switch

be heard as a sound

AM Tuner

The

AM tuner employs and an IC of IF amplification. block

(HA1138)

diagram

with 1-stage of

(see

page

8X-1

exist in

into AM

phase

and

of the actual FM

this AM component

to it, the

reflection

HA1137

13).

to ON during

refl ection.

a S-gang variable

Fig. 6 shows

55 for circuit).

Schmitd

can be

(audio

By setting the

to the audio

Dircuit

modulation)

existence

frequency)

SIGNAL meter

FM reception,

which

RF and 2-stage

the

25cl

the received

PM

and

signal

into

(and

determined.

are

FM

ampli-

indicates

capacitor

HA1138

It outprt

ciruuil

tl

,"/

c{

*),

lod

tatal

a

Fig. 6.

Block diagram

for HA1 l38

5. Circuitry of

Fig.

Fl\4

muting

t

I

4.2 AUDIO SECTION Equalizer Amplifier

The equalizer

(Ql

stage

amplifier is shown

&

is a PNP transistor

Q2)

differential amplifier. in the following

(C1

&

R1).

plementary voltage utility high maximum

stage

The output

symmetrical SEPP

factor of the SEPP

output voltage. Dynamic range

the equalizer amplifrer

High voltage

(Q3)

stage

is

therefore wide

in

by a bootstrap

(Q4

circuit. The

load input lettel at O.lVo distortion

lkHz).

at

Equalizer

elements

(C2,

C3,

R2, R3)

Fig. gain

&

Qb)

circuit

is

7. The ftst

unbalanced

provided

is

is a com-

provides

and over-

500mV

polysty-

are rene film capacitors with tolerances within and metal film resistors with

i1%.

These lead to a RIAA the balanced

playback

plus

input and the output

deviation with respect to the

standard

and minus

points

reducing click noise during

tolerances better than

within

t0.2dB.

power

supply,

become essentially 0V,

FUNCTION

operation.

circuit

high

(rms

117o

Due

the

switch

of

to

The TAPE program

the input at the

and

MONITOR 1

source

selectd

The TAPE MONITOR signal selected and the

input at the TAPE

by the TAPE

a

t":l':ffirno*'

stllcll

Fig.9.

When TAPE 1 REC PLAY TAPE 1

the

DUPLICATE

jacks,

PLAY

jacks

and

jack's

switch selects

by the function

TAPE 1

PLAY

2 switch selects

MONIIOR

2 PLAY

I

IIPI

Ptat tut

99

IY

oxJ.

rxitch

TaPe monitor

are

the TAPE 2 REC

(Fig.

Tltt I

-

switch

connected

10).

IlPt 2

between

jacks

between

jacks

2

ntt

oll-'"-

lrtrrotrToRz

ixilch

circuit

is set to ON,

to the TAPE

jacks

the

switch

(Fig.9).

the

1 switch

(Fig.9).

the

2

to the

Fig. 7. Schematic

Tape

and Adaptor

the

With

DUPLICATE

diagram

Circuits

source selected by the tained

at

the

TAPE REC

TAPI I

ntc

tnctior

sritch

8.

Fig.

R,

c" ["

t'

Equalizer

for

switch OFF,

the

function switches jacks

(Fig.

8).

TIPI 2

IrI

TAPE REC

jacks

amplifier

program

are ob-

signal selected

The switch

11). The signal and the

appears at

ADAPTOR

selected by

input at

tt t0 l0t 2

rritch

MODE Switch

When tion,

stage

the MODE the left and following the

Fig. 10.

Tape duplicate

by the

the ADAPTOR

switch

the TAPE

the A-DAPTOR

r0ltl||t

sritch

Fig. 1 1. ADAPTOR

switch

is set to the MONO

right channels

tape and

adaptor

circuit

TAPE MONITOR

jacks

OUT

IN

between

jacks

2 switch

(Fig.

selects

MONITOR

lll

iacks

shorted

are

circuits.

(Fig'

the

11)'

posi

in the

2

I i

I

,l

ll

ti

ir

14

-

A':o

BALANCE

A no-loss HB type variable tion is buffer in the following

Muting Circuit When the MUTING

position,

Loudness Circuit

This circuit is operated ON or NESS audibility characteristics volumes. tapped. enhances low and high frequencies at low volumes.

Tone Controls Twin tone

1250. These (sub)

BASS The signal is amplified

FET which a 2-stage NFB type

provided. the

main controls form the second stage of this circuit. is

applied to a

response becomes

in the feedback

stage is

Control

resistor at center

employed.

the signal is attenuated by 20dB.

switch

The VOLUME control variable resistor

Connecting a CR network at this

controls are

controls in addition

and TREBLE

and transistor direct coupled amplifier, after

The sub controls form

With NFB type tone controls,

shown in Fig. 12.

hpn

An

SEPP circuit is inserted

stage.

switch

and is intended to compensate for

consist of ultra-low

(main)

to required level by a 2-stage

single transistor amplifier. Frequency

variable by

circuit. The basic circuit of this

I, vn,

[,-

c,

is set

of the human ear at

employed with the SX-

to the conventional

controls.

tone control ctcuit is

t?

{P

c"

to the

by the LOUD-

OFF

and ultra-high

the first stage and

C-B

providing

0rt!!t

posi-

as a

-20dB

low

point

feedback

selectivity

n.

)

control

are considerably

above

circuit

VR2 slider

midrange, effec-

and

in Fig. 13

the circuits

change

any

Ttre NFB amount

gain

is also positions.

circuit

smaller

in

effect,

in

mid-

with

posi-

fixed

Fig. 12. Basic

Midrange The

Cl and C2 reactances

thal

VRl at frequencies tively shorting range,

opens the circuit.

comes equivalent respect parameters tion

is therefore without regard

C3 reactance

to the

of the

circuitry of NFB type tone

Operation

VRl. At frequencies below

midrange. In this figure,

are

not changed by

VR1 and VR2 sliders.

fixed and the

to VR1 and

I

c"

t. tt, [.

becomes large

Consequently, the circuit be-

to that shown

type

at low

Fig. 14.

by

NFB

type

and

gain

25Ct

fte-

This

greatly

gain

VR1.

at

C2

at

BX-1

Fig. 13. Midrange operation of

tone control circuit

Low

is

Frequency

The

reactance

quency reactance increases declines.

according at

High Frequency The considerably smaller high frequency in shorts that the same degree that the VR2

high frequencies

to

low

frequencies

Fig. 14. Low frequency

VR1 to from an

shown in Fig. 15.

NFB amount is now

slider

Fis. 15. FB type

Operation

of

form a circuit

Also,

to

VR1 slider

tone control

position.

High frequency operation of

tone

and

C1

in

the NFB

can therefore

Operation

comparison

can be varied by

control circuit

C2 increases

as shown in

proportion

amount

position.

operation of

circuit

reactance equivalent circuit such as

C3 reactance decreases in,

the frequency increases and

mainly controlled by the

Consequently, the

NFB

to the frequenry

varies

The circuit

be varied

of C1

with VRl effectively

VR2.

N

Tone Defeat By setting

described

Filter

Circuits ( Fig. 16)

These are NFB octave

Circuit

the TONE switch to OFF, the above

control circuit becomes bypassed.

tone

type active filters with

slopes.

The circuit combines a 2-stage CR

-12dB/

element and emitter follower. Normal function

the emitter follower is

and by 100%

NFB,

gain

NFB is cancelled in

quency, sponse. filter for low and high

emitter follower Power

Fig. 17 input amplifier, &

Q4

stage, Q6

of collector tween in

this circuit same between

cunent equal.

Q6.

Q4, cunents.

composing a

leads

This

to improved and sharper

response. In the actual circuit,

filters both employ the same

and each can be selected

Amplifier

shows

stage is

power

the

composed

with the input

differential

with

cunent

produces

Q5

cunent

base

Qb

type

transistors.

bases and

flows in

This results

Mutually

resulting

Q4

+fcc.

Q3

mirror.

and

amplifier

output composd

Connecting the produces

and emitter,

are

equal,

Consequently, emitters these

in equal

opposite

in

mutually

therefore

Q6

provided

becomes

in the

essentially

the area of the cutoff fre-

peak

in the frequency re-

amplifier

of

signal

&

Q1

applied to

Q2

comprise

at

collector

equivalent

of a diode.

a forward

biasing

while

of

Qb

Q6.

arrd

&

transistors

current flows

phase

signals

opposite

phase

operate as

passband

CR elements

ON-OFF.

section.

differential

e1. eg

the second

by

Q4

Qb

and base

voltage be-

and

Rl

are the

Q6

when voltages

are equal,

Q6

also become

in

Q3

drive

Q3

collector

push-pull.

"1".

CR

The

Q3 R2

and and

of

&

Fig. 16. Basic circuitry of

Power stage bias voltage

across D1, D2

drop resistor

for

power

and VR2. VR2

stage bias adjustment, and D2 are Varistors sation. A 3-stage Darlington

power

stage

Q11-Q14

(Q7-Q14),

in a complementary symmetrical

connection is employed in the

Il0[

filters

is supplied

by the is a semi-fixed

for temperature

with output

+

YcC,

sritch

tlLTIn

voltage

while D1

compen-

transistors

parallel

Fig. 17. Schematic diagram for

power

amplifier

:r€

ie

tlt

I

se

six-1

eE'c'

AO

connection. The

the balanced

LOOT> Because of this, circuit DC mined by resistor for fine adjustment voltage to compensate for irregularities in circuit elements.

SPEAKERS Switches

The SX-1250 is terminals

become taneously, to ON, the circuit functions as if all switches

OFF and the indicator lamps extinguish.

4.3

This circuit of overload, the speakers in case malfunction, and also when protection

(Fig.

DC NFB

voltage of the output center

(A,

overloaded

PROTECTION

power

the

18).

Porrr

output

plus

is

base voltage.

Ql

provided

B, C). Since the

when all 3 SPEAKERS switches are set

protects

supply is turned

circuit is composed

n|0lili!r

lcc

+

center

and minus

applied to

DC

if

all three sets are

CIRCUIT

the

performs

point

is

power

gain

VR1

of the center

with 3 sets of

power

supply, while

Q2

becomes OdB and

point

is a semi-fixed

transistors in case

power

of

a muting function

ON

of three

at 0V from

through

amplifier can

used

or

is

deter-

point

speaker

simul-

were

amplifier

The

OFF.

sections

R3.

flows

through the relay turn on the reverse appears OFF.

Q6 power

Q7 relay releases

circuit tums

Opetation by Detector Command from the one of D3, a cutrent through through declines according

Q5 QG

base releases and the becomes cut

supply voltage.

base

Note:

is

Q5

participate

then

becomes

potential

lcc

+

power

bias of

when the

remains

potential

OFF.

normally OFF

in

D4 or D5 and are applied in

flow.

R14,

on of these diodes, becomes

off.

base

Q6

power ON however,

drops and

and the

the muting operotion.

Q5

but

to the voltage

ON,

ON. C4 rapidly discharges and

drops, turning

power

coil, operating the relay

amplifier

from D6 &

C4 very rapidly

due

Circuit Comrnand

detector circuits

is

when a

Q6

output circuit. The

R19-R21 dis-

supply is set

due to the residual

Q7

power

to

bdse bias and does

normally reverse biased

large

Q5

potential

base

Q7

amplifier

from

turns

amplifier

pass

the

current flows

base

drop

OFF.

output

to

ON

discharges,

OFF. The

output

not

through

form

of

potential

at

R14.

rises and

Q7

The relay

circuit

a

Fig.

18. Block

1. Relay Driver Circuit

The relay driven by this circuit. It also function to OFF opening the output circuit detector circuits,

Muting Operation When reverse

OFF.

Q6 through R22 & R23,

seconds later. The collector

which

prevent

operation

power

the

biased through D6 and R19-R21,

Q7

diagram of

(Fig.

connects the

unpleasant noise during ON-

of the

supply

potential

base

protection

19)

power

on command from the

is

turned ON,

and

Q7

circuit

output

performs

supply as

rises as C4

turns

current of

ON

circuits is

a

muting

well

base

Q6

turning

charges

several

then

Q?

as

is

Fig. 19.

2, Overload Detector Shorting

impedance command

is

This

With the

is

Qa becomes

indicated potential

divided by

point

the (load).

C to

Ql

extremely

considerably lower difference current flows in

Schematic diagram

of the

to be sent to

illustrated in

output stage in

operating in

cut

by the

at this

Point

emitter through

small, the

forward biases

power

below the specified

off and the signal

solid arrows in

time

Rl and

potential

A

D is connected

D3.

relay driver circuit

of

Circuit

amplifier load

the relay

Fig. 20.

class B

positive

the

is

the

Also,

R3.

divided

R2 and

point C potential

point

than

Q1. Q1

operation, when

current flows as Fig. 20. Point D

point A potential

point

by

to

Q1

RE2. When RL

D. This

ts

l.5l

load

or a

value causes

circuit.

drive

half cycle,

potential

C

RE1

base and

tums

Qb

and

RL

point

becomes

potential

and

ON

a

is

\

operates

Qb becomes

the broken line

is biased

Q1 point

C and

point than that

flows in

If large ON due to the current due to

C

external noise.

in the negative

cut

off. The signal flows is indicated

by the

point

potential

point

of D3. current flows in

flows in

il..*'.i

lar

Fig.

20. Basic

arrows in

potential

E. If

RL

becomes

E.

Q1

RE1 and

D3. Cl

circuitrv

half cycle and

the center

difference

is extremely small,

considerably

tums

and

Qa

RE2 voltage drops,

prevents

of Fig. 20.

between

ON and current

Qb, Q1

faulty operation

becomes

luo,

for

overload detector

Qa

by

the

higher

and

Fig.

21. Basic potential

4.4

POWER

power

AII amplifier predriver former and right is also

fier and are for

supplied

lighted

stable illumination.

SUPPLY

supplied

secondary

channels

from

two

22,OOOpF

by

DC from a

circuitry

are regulated

stage.

windings

in the

an independent

for center

detector

CIRCUTT

Independent power

are employed

power capacitors.

regulated

point

up to the

stage.

Each channel

bridge

Position lamps

power

trans-

for left

recti-

supply

3. Center Point If a DC

of the

relay

principle.

Q3 the same

(Q3 if there the between tion, point. signal is absence When

point,

voltage

And

potential

D4, If the

increases collector

Current

potential

power

drive circuit.

and

difference

at

compose

Q4

input is

bases),

Q4

is a

difference

the two

an

AC

signal only is

As C2 reactance

applied

of output

a DC

potential

it

becomes

is negative,

the collector

Q4

drops,

DC

voltage is and curent

therefore

Potential

produced

is

amplifier,

Fig.

a differential

applied

no output

between

is amplified

collectors.

to

the

and

Qg

at the

is

the input

Q3

causing

positive,

potential

decreases

flows

Detector

at the

a

command is

21 shows

to both input

is

the terminal

and

becomes the

During normal

present

is

sufficiently

bases,

Q4

collector

produced

of

collector

current

Q3

drops,

and

through

Circuit

junction

sent to

this operating

amplifier.

present.

at the

low, the

resulting in

sides.

at

the

only. If the

Q3

current

increases

to flow

collector

while at

potential

the

D5.

point

the

When

terminals

However,

inputs, output

opera-

junction

same

an

junction

declines

and the

through

cunent

the

e4

rises.

Inrush

Ordinarily, the resistance ance former very low. of inrush A resistors is primary sevetal shorted Ihe 51 is the The Microtemp 52 is open

the

R1 and the

turned on, the

obtained

to close,

R1

temperature),

Current

power

of the air core.

used in the

the four 22,OOO1F capacitors

current

tens after

inrush suppressor

power

due to

heating

Suppressor Circuit

power

supply is

of the

Combined with

coil to

POWER

before

transformer

from the rectifier,

opens

transformer inrush

tumed

winding and instantaneous

In the toroidal

SX-1250, both

reach

can

therefore

suppress

of amperes.

power

is

a temperature

Microtemp.

relay

power

the Microtemp

thus

opening the

several hundred

provided

tlansformer

circuit is

switch and

power

primary

operates when

supply or relay

cunent

is

on

opposed by

induct-

power

these factors are

the high charging

in the in series

inrush

ttris

This resistor

excitation.

shown in

S2 a relay contact.

responding fuse.

is

turned on, connecting

coil

After

power

closing

(109'C

primary

DC

52.

cunent

secondary,

amperes.

with the

current to

becomes

Fig. 22.

in series

has been

current

If

32 fails

malfunction,

operating

circuit.

when

DC

trans

with

is

1E}

t

.Y

I

F!

Fig,

22. Basic circuitry

for inrush current

sx-1 eE'cl

suppressor

o

5. LEVEL

AUX

(

TAPE)

PHONO

t!ilc

IdBv]

30 20

I

0

l0

0

-20

DIAGRAM

I

i

tux

tt0,rv

i

|

Po'ilER

?

tN

rv

-----T------

SPEAKER

i

?-

/

/-

/

39v

I

-30

-40

-50

60

Mtu

b.5mv

PH0N0

2.smv

-

8. 3dB

/

/;

FREQUENCY: lkHz

t

f

BLOCK

6.

FM

75J}

UNBAL.

r

BAL.

3OOO

FM

AUX PHONO PHONO

L

GND

AM

1" 2

DIAGRAM

Cl

7rl

meter

TU

NING

I

I I

Buffer

-E*--f

ffi

ha

l--------

k

EQ.

I I

k

___J

AMPLIFIER

RIAA

meter

SIGNAL

Sgo

Sro

i

Srr

Srz Srs Sr+

l-

I

r

|APE

t--------l

REC

1

PLAY

rAPF_

r--------r

PLAY

REC

2

ADAPTOR

OUI

r--a

IN

-t

.l----+

PHONO

PHONO I

A

C

i20v

MIC

AUX

POWER

Srr Srz

2

Srg Sr+

I

AC

outtets

Power omp.

POWER

Rectif

ier

SUPPLY

Diol scole iilurnin..rtion

-

---+

AM

runer

f

tuner

FM

PO

siX-1

eEicl

Szg

Mutino Circuit

FM

r-

I I l-

L--ReA-

CONTROL

VOL

UME

Szz

f,

H,\1.l37

'_

r--

I I

I

_l

r-eltv

I

I I

I

J

I I I

SECTION

Detector

vcol

killer

Rotio

fAlo6lAP

Mul!ip!91Dgcg!.e1-

LPF

^o )12

SWITCHES

Sr

Bu

f

l'er

T 77r.

-l

-

200 kHz

tro,p

I

J

--

f-

T

I

srrnro

I

indi:otor

i

I

,

tA

h.

Jf-_- OUI

1,1

,

:

POWER

(

FUNCTION

AM

Stt:

F

Srz:

Sr3:

Sra:

S.rs:

Sre Srr: SrB:

Srg: Szo: Szr:

Szg:

M PH0N0 PH0N0 AUX

:

TAPE M0NIT0R TAPE fAPE ADAPTOR

MODE

MUTING

L0UDNESS

Szz:

T0NE

Sza:

LOW

SZS:

HIGH

)

1

Z/tvll}

1

MONiTOR

DUPLICATE

FILTER

2

(

sprRxERs

SZe: S zr

S

Zg

Szs Sso Set

I

SPEAKERS

:

PEAKERS

S

: S PEAKERS

:

FM

:

FM

MULT

:

DE.EMPHASIS

FM

A B C

MUTING

I PATIi

9

I

Sz: I

T*

I

Sz.t

I I I

I

,{

Szs

PRE OUT

POWqR

_

TREBLE

AMr_ry

__

---1

PROTECTION

r--f

i .l-"r-r. |

+ ,1

l€fl:il:i.,'

CIRCUT

Over-current

Relqy

AC

7,5V

!

J

drive

I

Hivi

":

OUT

PRE

SPEAKER

SPEAKER PHONES

SPEAKER

SPEAKER C

A

B

C

A

B

21

7. DISASSEM

Plate

Top Remove the six sctews

Wooden Cover Remove the two screws

BLY

(A)

(B)

detach the top

to

on each sideof the wooden cover.

plat€.

Bottom

Remove

Plate

the

fifteen

screws to detach

the

bottom

Fiq. 25

plate.

T

I

t

I

s

o

Front Panel

Loosen all Remove the three nuts from the sub-tone and

the setscrews of TUNING and

the knobs by

pulling.

Remove the

VOLUME knobs with a hexagonal wrench. Remove

two screws from the top edge of the front

panel.

volume control shafts.

6l

I

Loosen the

setscrews

Front

panel

Speakers Remove

Switch Assem

the four screwr

Filter Amplifi

Remove tlte t

sx-1

e5cl

Tone Amplifier Remove the three

Assembly

Flat

Remove the three screws

screws

Amplifier Assembly

(C).

(D).

Fis.28

;witcnnssemuryl

he four screws

Filter Amplifier Remove

the two

@

(E).

Assembly

screws

Function Switch Assembly

Remove the two screws

(F).

(G).

--#*"-ove

..'

Microphone Jack Assembly

the two screws

29

Fis.

(H)'

PARTS

8.

LOCATION

&1 FRONTPANELVIEW

(FILTER

Kmb

AAO.114

(SPEAKE

Knob

14

AAO.t

(SPEAKERS

Knob

AAD.114

(SPEAKERS

Knob

AAD.114

30Hzl

RS

C)

B)

A)-.

-Knob AAD.114

(FILTER

SkHz)

l

e5

Knob

AAD.113

(BASS

Knob

AAB-1q)

(BASS

Knob

AAB-IM

Knob

AAD.I13

(POWER)

sOHz)

looHzl

{TONE)-

Knob

(TREBLE

1916.1-

-i

AAB.1(x)

I

(TREBLE

Knob

AAB.l(x)

2OkHz)

"t

(FM

AAD.114

MULTIPATH}

(AM)

Knob AAD.114

(FM

AAD.I14

panel

AN8.386

MUTING)

a3s6rnbly

(FM)

Knob

I4

AAD.I

(PHONO

Knob AAD.I14

(PHONO

Knob AAD-I14

(AUXI

Knob

AAD-I14

(Tuning)

Knob A'iM-034

(MUTTNGI

AAD-113

(voLuME)

104

AAB-

l)

2/MlCl

(TAPE

AAO-113

(TAPE

AAD.113

MONITOR

OUPLICATE}

1}

(LOUDNESS)

AAD.113

(MODE)

AAD.113

Knob

{BALANCE}

AA8-1m

(ADAPTORI

AAD-I13

(TAPE

AAD-113

MONITOR

2}

T

rrl

8.2

REAR PANEL VIEW

a

Terminal AKB-O3O

Terminal AKB.O3O

Terminal AKB.O33

Bar'antenna

w72.O92

(TAPE

(INPUT)

Terminal AKE-012

2)

1)

(GND)

holder

0

Ferrite

ATB.O51

Terminal AKA.O04

slide switch ASH-015

bar-antenna

(ANTENNA)

(DE-EMPHAStS)

€ix-1

esc'

Connector socket AKP-OO7

Terminal

AKB,O3O

Terminal AKE.O14

Terminal AK8-030

(ADAPTOR)

(SPEAKERS)

(PRE/POWER

(REC/PLAY)

5P

AtVP)

power

AC ADG.O13

AC

socket

AKP.O05

Terminal AKB,O19

cord

(AC

(FM

OUTLETS)

DET

OUT)

8.4

BOTTOM

VIEW

Fl

1A

(FU

1)

(F

U2)

(FU3)

(FU4)

(F

U5)

Fuse 1A

AE K.106

Fuse lA

AEK.106

Fuse

AEK.106

Fuse 1A

AEK.106

Fuse LSA AEK,104

Function switch assembly

AWS.O94

{.

!.

6

)

\

I

Flat amplif ier assembly AWG.042

si)<-1

E!50

r&r

Ferrite

r22-025

F AE K.301

Power supply AWR.107

balun

124

use

amplif

Filter

AWM.O89

Speakers AWS.O95

switch assembly

(FU6,

ier

primary)

assembly

assemblY

lr

I

rl

d'

i''l

'l'

i'r

Ceramic ACG

Control

AWG.O41

capacitor

003

amplif

(0.01/r

F 150V)

ier assembly