Pioneer SX-3700, SX-820 Service manual

,a

rilf

EefvicecTlanual

a

STEREO

RECEIVER

sSx-37cIcI

sx-8ecl

()rqoru€Err

MODEL SX-3700

COMES

IN FOUR VERSIONS DISTINGUISHED AS FOLLOWS.

Typ. Voltag.

KU 120V only U.S.A. model

'|

20V only Can€da

11OV

12OV

,

1 1OV . 12OV

is applicable

end 24OV

,22OV ,

22OV , and 240V

,

(Switchabls)

(

Switcha

ble )

to the SX-3700/KU.

Gen€ral

U.S. Military mod6l

For

e

KC

This

service manual

refer

to the additional service manual.

CONTENTS

1. SPECTF |CATTONS
FRONT

2.

3. BLOCK DIAGRAM

4.

CIRCUIT DESCR IPTIONS

4.1 FM Tuner

4.2 AM

4.3 Display

4.4 Equalizer

4.5

4.6 Power Amplif

4.7 Power Indicator

4.8 Protection
DISASSEMBLY

5.

6. PARTS

PANEL FACILITIES

Tuner

Tone Control Amplifier

LOCATION

...........

Circuit . .

Amplif ier

ier . . .... ...

Circuit .. -.

Cirorit . . . . . . -.

......

. , . .

. . . . . . .

. . . .

2

..4
..6

..8
. 11

11

.

11

.

11

.

11

.

13

.
.14

7. DIAL

8. ADJUSTMENTS

8.1

8.2

8.3

8.4

9. SCHEMATIC DIAGRAMS, P,C. BOARD
CONNECTION DIAGRAM AND

LIST

9.1 Schematic

9.2 P.C. Board Conneaion Oiagram . . .

9.3 PansList.....

1O. PACKING

11. EXPLODEOVIEW....

12. ADDITIONAL

Ramarks

model

exDort model

servicing of the other

STRINGING

CORD

FM

Tuner

AM

Tuner

ldle

Current Adiustment

FL

IndicatorCircuit

Diagram

SERVICE

...

.

MANUAL SX.82O

types,

-.......

PARTS

please

......16

41

l'

17
18
19
19

21
za
30
34

J5

l

1.

SPECIFICATIONS

six-37C'c'

A

t

,A

A

A

Amplifier

Continuous

nel,

Hertz with n0 more

Section

at 8 ohms

min.,

power

output of

45watts-

from

20Hertz

than0.0?%

d i stort ion .

Harmonic

Total
8 ohms,

Intermodulation
4 : 1, 8 ohms,

Damping

f rom

continuous

per

watts

22.5

continuous

22,5 watts

per

Factor

AUX)

rated

from

rated

Oistortion

Dower

channel

Distortion

oower

channel

(20

(20

Hertz to 20,000 Hertz.

outout

power

AUX)

output

power

Hertz to 20,000 Hertz, S ohms)

. .

output

......

(50

Hertz : 7,0O0 Henz

. .

output

...... Nomorethan0.02%

,"o,irs"",i,i"'ir),;;";;;";;

PHONO

AUX,TAPEPLAY 1,2

Phono

PHONO.

Output

TAPE REC 1,2 -.. .
Speaker

Frequency Response

PHONO

AUX, TAPE

Tone Control

BASS

TREBLE.
Subsonic Filter
Loudness Contour

Hum and Noise

PHONO

AUX,TAPE PLAY 1.2,.

FM Tuner

Usable
50dB

MONO

STEREO

Signal-to-Noise Ratio

t\40No

STEREO,

.

.......'l50mv/50kilohms

Overload Level

.

(R

IAA

PLAY

,,.

. ........79d8

(T.H.O.0.02%,

Equalization)

2

1,

(Volume

(lHF,

control set at

......

short-circuited.

. . 20Hz to 20.000H2

. . .

.....

.....

.....

..... 95dB

Section

Sensitivity

Ou ieting Sensitivity

..

.

(lHF)

. . .

.

.

lOHzto IOO,OOOHZ]]dB

per

chan.

to 20,000

harmonic

total

No more than 0.02%

Nomorethan0,02%

=

No more than

0.02%

""

2.5mV/50 kilohms
1,000H2)

250mV

l50mV

A, B, A+B

10.2d8

(100H2)

iSdB

(10,000H2)

iSdB

(-tuB/oct)

15Hz

-40d8

+6dB{100H2)

A network)

10.3dBf

15dBf

37dBJ

80dB
75dB

position)

(1.8pV)

(3.1l]V)
(39pV)

65dBf)

{at
(at

85dBf)

Distortion

MONO

STEREO

Capture Ratio
Alternate Channel Selectivity

400kHz.

Stereo Separation

l kHz

30Hz to l5kHz

Frequency Response

Spurious Response Ratio

lmage Response

lF Response Ratio
AN4Suppression Ratio.

SubcarrierProductRatio .. . . . .

SCA Rejection Ratio.
Muting Threshold
Antenna

AM Tuner

Sensitivity

Selectivity

Signal-to-Noise Ratio. ......

lmage

lF Response Ratio
Antenna.

(at

65dBf)

l00Hz ........

1kH2.........

6kHz.........

,IOOHZ

1kHZ.........

6kH2.........

.

..... .

Ratio ...

. . .

Input

. . .,.

.. . . ...

.. . . . . . .

Section

(lHF,

Ferrite Antenna)

(lHF,

Ext.

antenna) . .

Besponse Ratio,....

. . .

o.'t70

o.o7./"

0.15%

o.2y,
o.15%
o.25%

1.ft8

75d

B

.45d8
.35d8

. 2OHz to lskHz]3

. 65dB
.65d8

.90d8
.55dB
. 50dB
.65dB
. 19.2dBf
. 300

75

. 300rrV/m

.. 15pV

27dB

..

52dB

. .

. .

. . .

. . 32dB
. . 40d8

Ferrite loopstick antenna

(spv)

ohms balanced,

ohms unbalanced.

3dB

Miscellaneous

Power

Requirements

PowerConsumption
Dimensions .. 480(W) x 145(H) x364(D)mm

Weight

(without

..........

... .....

18-14/16(W)

package)

AC 120V.60H2
290W(UL)

x 5-11/16{H)

x 14-5l16(D}in

11.6k9

{25

lb 9oz)

Furnished Parts

Operatinginstructions ...,,.... 1

FMT-typeantenna

*Measured

Regulation

NOTE:
Specifications and the design
without notice due to improvements.

pursuant

tule on

...........

to the

Power

Output Claims

Federal Trcde

subject

1

commission's

for Amplifie6.

possible

to

Trade

modifications

2. FRONT

PANEL

FACILITIES

PowER

O

Set this
There will be a
the muting circuit has
unpleasant

power

SPEAKER

@

Depress the
nected to
panel.
You

can depress both
sound from
time.

POWER

@

This meter

on the fluorescent display
nominal impedance
speaker terminals.

DIAL

O

pointer

This

ouARTz

@

This indicator

has

been obtained

stabilized bv the

FM

@

This indicator

program.

swrrcH

switch to ON to supply

delay

short

noise that is

is

switched on and off.

swITcHEs

switch corresponding to

the SPEAKERS terminals

of these buttons to listen

pairs

two

METER

you

allows

POINTER

indicates the broadcasting

LocKED rNDrcAToR

lights up after the optimum

STEREO INOICATOR

lights up when receiving

to

of I ohms

displays

and

built-in ouartz lock circuit.

power

to the

when it is set to ON. because

been actuated

sometimes

oi

speaker systems at the

read

out the rated

tube when

that the

to suppress the

generated

the speakers con-

(A

or B) on the rear

speakers with a

are connected to the

stations.

receiving

power

tuning

FM

an

receiver.

when

the

to the

same

level

point

state is

stereo

SIGNAL

@

This indicator lights
during
ance with the
The optimum tuning
number of indicators light.

TUNING INDICAToR

@

When

tuning in an FM

point

is

When

the left indicator has come on,

knob

slightly clockwise. When the right indicator

rotate

on.

FREOUENCY

@

This indicates the frequency which is tuned.
With FM reception,
of the display and

"AlV"

tion.
These
changed.

TUNING

@

Use

this

HEADPHONES

O

Plug

the headphones
listen through
Release both speaker switches ii

the

sound through

INDtcAToR

in sequence

the tuning

indicated

the

of an AM or

strength of the signals being received.

point

station.

when the

knob

slightly counterclockwise.

DISPLAY

the letters

"MHz"

appears

change when the function

on

the

KNOB

knob

to tune in to broadcastinq

JACK

into this

your

stereo headphones.

your

headphones

from

FM

is where

the optimum reception

center indicator

"FM"

on the right. With AM recep-

left

and

jack

you

broadcast in

appear on the left

"kHz"
selector

when

want to

only.

left through right

accord-

the maximum

lights

up.

rotate

the tuning

comes

on the

stations.

you

right.

position

want to

listen to

T

is

six-37clcl

]^

.r.

\A

a

q}'..

BNSS AND TREBLE

@

Use these controls to adjust the bass
turn the bass control to the

you

tion,
frequency range. Conversely,
left
You
high-trequency range.

@

When this switch is
can
that
which is

table and other

cannot be heard, it can

tion and damage the

@

Employ for tape

progress.

1: Playback or monitoring of a tape deck connected

2:

NOTE:

L Be sure to set the switches to the uppet

2. When lecording with two tape decks

@

Depress the function
program

before selecting a different function
sound

FM:
AM:
AUX:

PHONO:

NOTE:
Only one function switch should be deptessed at a time.

will be able to emphasize the sound in

from

the center

can use the treble

LOW

rape

FILTER

provided

be

you

can cancel out noise in the ultra-low frequencies
generated

MoNtroR

the TAPE 1
Playback
the TAPE

playing

when

opefate the tape monitor I switch as
signal to the TAPE 2 deck.

(0)

SWITCH

set to

for frequencies

by low-pitched rumble from

forms

of distortion. Although this noise

speakers.

playback

jacks.

or monitoring of a tape deck connected to

2

iacks.

rccords or

FUNCTION SELECTOR

source. Turn the volume control down first

trom

program

one

Depress this switch

Depress this

Depress this
audio component
AUX

Oepress this switch
cord

PHONO

coNTRoLS

and the treble.

right

from itscenter

turning this control to the

position

control

generate

willattenuate the

to adiust

'lsHz.

below 15H2. This means

the sound

a 6dB/oct attenuation

intermodulation distor-

{0)

the

a turn-

swrrcHEs

or to monitor a recording in

(OFF)

position

listeninq to

switch which corresponds to the

source is being reproduced.

jacks.

on the turntable connected to the

iacks.

brcadcasts.

simultaneously,

switch

when listening

switch

will interupt the

this

switch

for FM
for

connected to the

when

while

broadcasts.

AM broadcasts.

playing

you

lf

posi-

low-

sound.

in

the

to

do not

the

to an

re-

a

enlnNce

@

Use

this control

right

channels.

switch

to MONO/OFF.

on the right, it means

higher.

is
Conversely, if the
it
Therefore,
adjust. After adjusting.
switch to STE REO/ON.

@

This

the mode
STEREO/ON

while

interstation
listening
MONO/OFF

mode. while the FM muting function
enabling
tuning in to the FM broadcasting

NOTE:

Recoding
the MONO/OFF

@

When
trol
accentuated.
When
hear
switch is
By depressing
more
the volume control is

@

Use this control

and

put

Turn

means

MODE/FM MUTING SWITCH

switch is a combination of the

the

to

suitable reception of weak radio

LOUDNESS

listening

turned down, depress

the

the bass than when

thus designed to compensate

strongly and the

VOLUME

headphones.

level. No

coNTRoL

to balance the volume

First,

however,

lf the

that the volume

the balance control to

sound appears to be louder

that the volume

turn the balance

select switch.

position

F l\il

muting function acts to suppress unpleasant

noise while tuning between FM

FM

position,

stercophonically

the reproduction is

broadcasting. When

however,

position

may

SWITCH

perlormance

to a

volume

low,

is

this switch, the bass come through much

sound

turned down,

CONTROL

to adjust the output level to

Turn it

sound will be heard if

set the mode/FM muting

sound appears to be louder

of the left channel is higher.

control to the right

return the mode/Fl\4

When setting this switch at

reproduction is in mono

station.

with

the

the

mode/FM muting

the

cause deteriorction in channel se-

this switch and the bass

human

volume is high.

takes on a

clockwise to increase the

of the left and

right

ot the

the left and adiust.

F l\il muting

jn

setting this switch at

does not act, thus

with the

finds

ear

for

this deliciency.

punch

you

set

channel

on the leJt,

muting

switch and

mode,

stereo

stations

stations

volume

The

it

when

when

swiach

will

it harder to

loudness

even when

the speakers

"0."

to

and

in

con-

be

out-

5

BLOCK

3.

RF

Block

STEREO

AM

OUT

DIAGRAM

(NAt201)

c

]NOICATOR IUEE

AF Block

t;

REC F.AY R€C PLAY

R

CHANNEL ( SAME

AS

L CHANNEL)

r$

SPEA(ER B

HEAo

ll

a i,BfffiJ*

G)

o

r

six-37ClC'

-)A

-\-A

4.

CIRCUIT

4.1 FM TUNER
Front End

FM front

The

ganged
equipped 1-stage RF
Clapp circuit
voltage controled

(variable
system
operation, a constant
diode.

lF Amplif

filters. The IC

,)

stitutes a

limiting

stage,
(PA3001-A),

quadrature

cuits.
ratio, delay
shows a marked improvement in

the
Multiplex Decoder

(PA4006-A)
functions in a

functions
(PA1001-A)

further improved by incorporating a chopper
MPX

(see
either to

t

eliminating the
distorition. Furthermore, since the
tures

tuning capacitor, a dual-gate

local oscillator. This oscillator is

capacitance diode). When the

(refer

These employ 3 ICs

an

Performance in terms of distortion,

PA3001-A.

The recently developed multiplex

Distortion

decoder.

Fig. 4-1) operates by switching

DC

to

ier and Detector

(HA1201)

single-stage differential amplifier current-

limiter. The IC

improvement on the

includes an IF

detector, meter drive, and

characteristics, and other

combines

of

the

and AF MUTING

ratings

The

ground

generation

direct{oupled

DESCRIPTIONS

of

end

oscillator employing a vari-cap

"Quartz-lock

single IC, thereby

more conventional

chopper type

or to

SX-3700

amplifier, and a modified

voltage is applied to

and 3 dual-element ceramic

of the first 2 stage con-

(PA3007-A)

former IF system IC

MPX

decoding

S/N ratio have been

and

the through circuit, thereby

of

switching with the detec-

includes a 3

MOS EFT-

quartz-lock

system") is not in

in

the third

limiter amplifier,

other cir-

parameters,

comparison to

decoder

lvith muting

handling the

MPX IC

(PA1002-A).

IC

switching circuit

the signal

unwanted nois€ or

PA4006-A fea-

the

S/N

IC

type

at the

circuits,

signal cancel-

the

MUT

and

VCO

ctcuit.

separation

in

muting

pilot

the

killer circuit,

there is

tor,

frequency end.

low

Besides
PA4006-A also incorporates
ler, stereo

a

amolifier. and

Composite

no

deterioration

decoder

the

auto selector,

MUT

control

signal

4l1i\r1l''

InoutffiOutOut

-ri:-'',

JlIlIl[JlIUUrn ^---a

s* iiit''i'iri

4-1 Chopper type switching circuit

Fig.

Ouartz-Lock System

quartzJock system

The

stereo receiver is

employing
in the
DC voltage by
crystal resonator),
frequency
locked.
control system
remain

When
IF system
applied
consists
resonance
tor.

frequency

at this time

being
quency

a crystal

intermediate

This extremely

tuned securely

the IF signal

to crystal
of diodes

clcuit equipped

The resonance

(10.7MH2),

reduced

increases,

a frequency

the discriminator

being

thus ensures

(PA3007-A),

IC

will be

to a minimum

the

"--\y'

i r

featured in

resonator.

frequency

resulting in

conected

stable

that tuned
long as required'

for as

appears

detector

connected

frequency is

which

minimal, resulting

reactance

i

-

7

,,T

SX-3700

the

servocontrol

Any displacement

(IF)

is

(equipped with a
the local
and

frequency

pin

at

is amplified

it

(see Fig.4-2) which

parallel

in

with a crystal

the same

means the

level. If

of the canacitance

system

detected

subs€quently

frequencies

no.17

impedance

in the

the input

as a

oscillator

servo-

of the

and

in a series

resona-

as the

output

fre-

IF

----f::,

-"

'''i'ill

(!r

t5

DETECTOR

r:

I I I

,t

?-J

I

CRYSTAL

|

| +:

t:

;i..*'F--?-'i+r

ITNATOR = rll'
t_-----F-- I | ;

l_

(C)

stage
ductance
detection
of

the IF signal. If the input frequency
L stage reactance is decreased
ance increased,
which leaves
The L stage
the
is

increased, resulting in
the detector
characteristics, FM
Since

deviation
about a central
is equal

output DC level

any displacement
quency

become asymmetrical,
of a DC

LPF1

correction voltage
capacitance diode in
correcting
constant IF

Since
tor is regulated
quencies

r

Limiting the t ocking

If
overlap with strong
cies and result in considerable
A DC amplifier

(limiter
restricts
tance diode, thereby limiting the

A DC
system IC
level drops below
quency
This
the
ing in the FET
lock circuit being

4.2

The AM
capacitor,
transistor

(converter),

4.3 DISPLAY
Frequency

Frequencies

is reduced,

stage

by D2

the negative

and C stage reactances

degree of detuning in the respective

output. By thus attaining

IF

the

to the resonance frequency,

deviation

voltage. This DC voltage

(IF

the central frequency

the

action

the

has

DC

gate

of

signal is an FM signal

due

to

filter)

the

(i.e.

of extremely high

quartzJock

by

voltage

voltage appears at

(PA3007-A)

been detuned by more

voltage

(FET)

Q2

and the

(L)

increased,

which leaves the

resulting in AM detection by D1

detection

modulation it will

axis. And if the central frequency

will be zero. If, however,

in the central

in respect to

resulting in

and LPF2

which is applied

the

oscillator

a constant

by the crystal resonator,

Range

range

adjacent broadcasting frequen-

is therefore used as a limiter

NFB

circuit zener

applied to the variable

SpV, or when the tuned fre-

(FM

muting

via

being turned on, and

tumed off .

reactance

and C stage react-

portion

a subs€quent increase in

becomes

(AC

local

oscillator,

frequency

tuned

of the crystal det€c-

stability

is too wide, it

tuning

pin

when the antenna

signal) is applied

a Schmitt circuit, result-

AM TUNER

tuner stage
a singleclement
RF amplifier, a PNP

and an NPN transistor

CIRCUIT

Display

received

employs a

ceramic filter,

by

the SX-3700 are

of the in-

resulting in AM

positive portion

decreases,

of the IF signal.

increase as

directions

S-cuwe

possible.

frequency

symmetrical

be

the

detector

there is

frequency, fre-

detector

the

generation

the

passed

is
filter)

frequency).

quartz-lock

no.13 of the IF

to form a

to the variable

to obtain a

tuned fre-

are obtained.

difficulties.

diodes) which

than 1 100kHz.

the

will

through

thereby

will

capaci

range.

input

quartz-

2-ganged tuning

NPN

an

transistor mixer

IF amplifier.

dis-

to

played
tube
ments
from 0
digit which

in digital

(FL

-

(a

to 9

tube). Each digit employs up to 7 seg-

g)

employs

form

(see

Fig.

(with

the exception of the left hand

only 2

fluorescent

by

4-3) to display all numerals

segments b and c).

Lt

ti

d

Fig. 4-3

The

signal source
tion is the local oscillator.
a buffer
(M54451P)
sion
applied to the frequency
This IC is responsible
?-segment 5-digit
on according to

An outline of the

given
FL

tube a
nected in
signals
pendent
being lit up
Each

osc,sr6NAL

OSC.SIGNAL

val. Pin
terminal. The time
8009s

level signals,

L
tube
period).

tube
ness may

The
basic signal used
division
control

amplifier

where it is

(1/8

for AM and 1/80 for FM)

in block diagram form

-

g

segments

parallel,

(see

Fig. 4-6)

grid

for each digit) result

in succession from the left hand

digit is lit up for

Fig.

4-4 Frequency

no.7 of PD5009

for H

brightness

is driven by static drive, the degree of bright-

level input signals,

Note

varied

be

5.12MHz crystal oscillator
pulse

signal and the counter

signal.

7-segment

during both AM and

(FET)

subjected to

for the dynamic

display

time-shared sequential

composition of

D1 - D5

the

applied to each

1ms during each 5ms

sr.NAL

division

thereby varying the degree of FL

(by

varying the segment lighting

that since the

by changing the

in the

display

The signal is

to the

frequency

counter IC

(each

(anode)

display block

is the brightness selector

preparation

digit being

Fig. 4-5. With

in

for

each digit con-

time

division

in the digits

FL luB€

diagram

pulse

width is set to

and to 2009s

power

indicator

grid

generates

indicator

FM

recep-

passed

prescalar

before being

(PD5009).

drive of the

scanning).

PD5009

grid

voltage.

of the time

gate

via

IC

divi-

tumed

the

pulse

(inde-

side.

inter-

for

FL

the

circuit

is

r

sx-37c'cl

l;

(^,

\

t,

+1,.

Terminals S1 - 54
designating reception
modes
designated
levels
mode are required
IF
during

employed in the SX-3700

by varying the

(H

and L). The 3 different IFs during

in coping with IF

ceramic

filter stage, S3

FM mode according

(pin

nos. 3

mode.

combination

-6)

are used in

The 2 reception

(see

Table 1) are

offset in the

54 being

and

to the

ceramic filter

of input

FM

preset

characteristics .

Although the SX-3700

FM stage

quartzJock
system is capable of locking any frequency within
the FM band, the 10kHz digit

decimal

place)

in

FM frequency display will

the

(digit

in the second

appear only as 5 or 0.

The frequency

the TUNING

display

and
though the segrnents
are static
cuits, the
division

driven by the

grid

is

driven according to

pr:lse

timing,

Fig.

4.6 D1.D5 time division

FL tube also incorporates

SIGNAL

(anode)

indicators. And al-

for

these indicators

corresponding drive cir-

the D3 time

thereby

placing

gC=

H

pulse

the segments

(ARIGHT,

signals

PRESETABLE

OECIMAL COUNTER

22-BlT r 15

under

dynamic drive. In addition, the AM and
indicators in the frequency
according to the Db timing,
MHz

indicators are lit according to the

MODE st

H H 10.73
H
H

L

TUNI NG Indicator

The TUNING indicator
tuning indicator
casting
2

station

frequency

detuning direction indicators

5-OIGIT

ROM

s2

L
L

H L

Circuit

(which

lighLs up when a broad-

display section are lit

while the

s3

H

H H

consists of a center

properly

is

which
direction in which the station has
from. The corresponding
lined in Fig.

The
station has
center frequency.
and

Q21

ferential amplifier
and

Q14

signal appearing at
(PA3007-A)

(Q15
more

than

4-7.

TUNING indicator

been tuned to

This is because

(resulting

tumed

off

IQ19

being tumed

pin

passed

and

&

when the station is tuned away by

Q16)

t

100kHz.

drive circuits are out-

activated once

is

within

in the detector dif-

&

Q20l

on) by the

no.13 of the IF system IC

via the Schmitt

FM

kHz

and

D1

timing.

s4 lF

{MHz)

't0.70
'r0.67

450k Hz

Table

tuned)

and

indicate the

been tuned away

t

100kHz of

is tumed on

Q22

being tumed off

FM

muting

circuit

1

the
the

The DC voltage
scribes
a
pin

voltage
(Q19

tors switch

an S

particular

no.2

serving

is amplified by

&

Q20)

SCHMiTT

curve when tuning

broadcasting

circuit

pin

on

frequency,

as the reference

the differential

and then

(Q16

applied
&

Q26).

no.4

of PA300?-A

to

to a

and

away from

the voltage

level.

This DC

amplifier

poladty

de-

on

detec-

and

the higher frequency

ing direction

on the other hand, the broadcasting frequency
approached from the low frequency
tuning away to a lower frequency) the
voltage
on to light up the
detuning

is on, the

Q26
resulting in

off,

which

not be lit up.

will

Once the broadcasting frequency has been tuned
properly,
equal.
turned off, which means that neither of
ing direction indicators will be on in this case. And
since

Q14

base voltage,
tuning indicator light up.
charged up via R84, resulting in
on, thereby lighting up the
cator

LED.

indicator

will be

Consequently,

lower, resulting

lower

direction indicator.

Q14

being turned on and

Q14

means that

voltages

the

is turned off because of

will

Q18

(right

hand

also being

frequency

base voltage

the center tuning

on

Q16

be turned

turned on.

side

in

Q16

(left

When

pin

and

Furthermore,

Quartz

either

will be

nos.2 & 4 will be

Q26

the decreased

on, and

Q23

side) detun-

When,

(or

when

pin

no.4

being turned

hand side)

or

Q16

high,

turned

Q18

indicator

will both be

the detun-

the center

C16

tumed

being

Locked indi-

is

is

Fig.

4-7 TUNING indicator

When

quency
to a

be
voltage will thus
voltage raised, resulting

tuning to a frequency from

(or

higher

higher

side

than that on

tuning away from

frequency),

pin

be lowered and the

voltage

the

no.2. The

in

Q26

driver

circuit

the

the frequency

pin

on

Q20
Q19

being

turned on,

high

fre-

no.4 will

collector

collector

SIGNAL Indicator

The

SX-3700

FL

tube

5-point indicator

drive

signal obtained

(P43007-A)
then applied
This IC
similar to
circuit, 5 of
SIGNAL indicator.

contains

those employed

SIGNAL

and AM
to

the indicator drive

12

these

Circuit

indicator consists

display. The signal

from the FM

tuner is first amplified

pairs

of voltage comparators

in the

pairs

being used to

IF system IC

IC

power

of an

meter

and

(HA12010).

indicator

drive the

r

Fig. 4-8

SIGNAL indicator driver circuit

F

EOUALIZER AMPLIFIER

4.4
NFB

This circuit

with
(M5214L-P).

and

performance
a voltage
dynamic
of 250mV
79dB
within t 0.2dB

4.5 TONE CONTROL

fier with newly
(M5214L-P).

4.6

amplifier. The

(Q3),
employing an
rent mirror

stage, v/hich

harmonics

circuit

provides

complementary

of 45W
O.O2%,2OHz-2OkHz\.

newly developed

This IC

provide

(at

circuit

This

POWER

This is the basic circuit

the load circuit of which

pre-driver

The

(D5,

power

The

is an

is a low-noise and

openloop

an

specifications

gain

margin or maxirnum

(lkHz,

2.5mV

AMPLIFIER

provides push-pull

and

Q11),
voltage

high

(8O

load. at both

35.5dB

of

O.O2Vo

input, IHF-A),

(2OHz

is

NPN

serves
further increase

stage

-

NFB type tone

an

developed

first stage is a differential amplifier

twin

stage

enables

gain.

is a

SEPP ctcuit,

equalizer amplifier

type

performance

high

low distortion

gain

2OkHz).

AMPLIFIER

transistor

to

(Q7)

Darlington connection

105dB. The main

of

for this circuit include

(at

lkHz), a

allowable input

THD),

high

arrangement of

cancel even

with a current

stable operation

channels driven,

S/N ratio

and equalization

control ampli-

performance IC

is

a current

(Qb).

operation

gain.

and

The cur-

numbered

has an output

IC

type,

phono

level

power

mirror

in

this

mirror

and

pure

THD

of

POWER INDICATOR CIRCUIT

4.7
The SX-3700

fluorescent
thermionic
celerated
segmental anodes,
This tube

other symbols.

An

Fig.

in

pin
tains a detector

peak
The

40dB to obtain a

by

The output
tube are driven
channel)
amplifiers.
ing levels, so

operate
since these amplifiers
put power

segment will
rises.

4.8 PROTECTION CIRCUIT
In order to

speakers,

protection

automatically
As can be seen
of 3

into the
is used to

outline of the

4-9.

(4)

no.6

hold circuit for

dynamic range

equipped with

separately

the SX-3700

main component

output

indicator tube

emissions

resulting in

The output

of the

circuit,

power

by the

These amplifiers

each amplifier will

as the input

indicator

light up in tum

protect

circuit which

by a relay

from

power

(FL

from

fluorescent substance

indicate numerals.

FL tube drive circuit

circuit signal is

(TA7318P-A).

IC

compressor

both left and

of the signal is

"peak

held"

indicator segments

HA12010 ICs

12

apply the

segments, each

both the amplifier

has been equipped

is opened and

Fig. 4-11, this circuit

parts.

Eix-37c'Cl

indicators

tube).

the

the emission

pairs

are biased

level increases.

in the output

In this

cathode

letters,

applied to

The

(40dB)'

right channels.

thus contracted

DC voltage.

(one

of differential

at increas-

commence

voltage to the out"

successive

as the input

feature

tube,

are ac-

of the

of light.

and

is shown

IC con-

and

of the

for each

And

level

and the

with a

closed

circuit.

consists

FL

to

T^

fD

(fafatSP)

)c

OE

TECIOR

t/2

gE

FLUORESCEN

Fig. 4-9 Power indicator circlrit

I ]NDICAIOR

TU

ac

7 .2v

The relay
delaying
on, opening
tumed
to instructions

power

the
via R8,
across
difference

on due
the

off, C4 is
ing

being opened.
10 below consists

load

by the
opposite comers

value
be

on

charged
tumed

the capacitor

relay contacts.

in

The overload

RL

drops

tumed on

C4

drive circuit

relay

closure

the relay

off, and

thereby increasing

to

Q6

forming

potential

in

via

off and

a.lso opening the relay

from

is first switched

exceeds

the forward

discharged rapidly

being

detector circuit

below a

due to forward

the relay

D3

the relay contacts

controls relay operation,

when the

quickly

each detector

terminals. Once

the zener diode,

When the

tumed off and

of a Wheatstone

one

of the arms.
difference
of the bridge

certain fixed level,

drive circuit

and

Q3,

when the

on,

potential

the

biasing, thereby closing

via

betyyeen

biasing. The charge

resulting

power

C4

power

Db

the relay contacts

outlined in Fig. 4-

circuit. If

is switched

power

in response

circuit.

is

this
Q6

and

bridge with

Q3

diametrically

will thus be dis-

in

being opened.

When

charged up

difference

potential

is turned

is switched

result-

R7,

the

is

biased

the RL

will

Q3

being

Q6

If for

the output, it

is

detector
being
Rb
normal signal
application
and
output, it is

to

Q4

to
the
of
be tumed
ly,

Q6
opened. If

output,
while
since a negative

Q5
contacts

any reason a DC voltage

will be detected

circuit, resulting in

opened to

and C2 form a low-pass

of signal voltages

If

Q5.

and

ground,

reverse bias

Q4
the base of

being turned

Q5

in

this situation,

a

Q5.

this transistor

is

connected

on due to a forward

a negative DC voltage

is tumed

Q4

is

tumed on due to a forward

ooened.

thereby

components,

positive

divided by

Since the

applied.

Q6

voltage is

DC voltage

ground,

to

grounded

is

off and the

off due to a reverse

is tumed

Q6

R5 and R6, and applied

the relay

protect
filter
thereby

to

base of

will remain off

And since the emitter

by

relay contacts

applied to the

generated

is

by the DC voltage

contacts

the speakers.

designed to block

preventing

the bases of

appears at the

is connected

Q5

this transistor

bias.

Consequent-

resulting in

Q4,

appears at the

bias.
emitter of

off and the relay

at

the

Q4

due to

will

being

bias,

And

Fig.4-10

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