Akai GX-635 D Service Manual

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f1't'

SERVilCEMANUAT

3

PARTS

LIST

B

'roDEr

GX.635D

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STEREO

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SECTION 1 SERVICE
SECTION2
SECTION3

PARTS LIST..
SCHEMATIC

TAPE

GX'635D

MANUAL.

DIAGRAM

DECI(

I

........43

......67

TECHNICAL

I.

DATA

TRACK

SYSTEM
REEL CAPACITY
TAPE SPEED

& FLUTTER

WOW

FREQUENCY

DISTORTION

SIGNAL

ERASE
CROSS
CHANNEL

FREQUENCY

BIAS

RESPONSE

(1.000

TO NOISE

RATIO

TALK

SEPARATION

HEADS

MOTORS

TIME COUNTER

REAL
FF & RWD

OUTPUT

TIME

JACKS

INPUT JACKS

DIN JACK
DIMENSIONS

WEIGHT

POWER

REQUIREMENT

"0"

Hz

RATIO

VU)

2 channel

4 lrack

to 10-l/2"

Up

x0.8%

19 cm/s

cm/s

9.5
(Pitch

control: more

than 0.03%

Less

than

Less

than

Less

than 0.10%

Less

to 27,000

30

21,000 Hz

30 to

to 25,000

30

to

30

19.000

than 05%

Less

than 62

Better

than 70 dB

Better
Better than

than 55 dB

Better

kHz

100

(6):

Two GX

(3):

One

to 99

Up

using 550m

sec

120

(2):

Line

Required

(1):

Phone
Microphone

stereo/monaural

reel

-l12

(7

(3-314

xl.0%

WRMS at
WRMS at 9.5

0.04%
DIN

0.08%

DIN

13

dB at 19

Hz

13

dB at 9.5

t3

dB at 19

Hz
Hz 13 dB

aI 19

dB DIN

(at
(at

40

dB

(at

Recording

AC Servo Motor
min 59 sec,

(0

0.775V

load impedance:

mV/8 ohms

100

(2):

0.25

Required microphone

(2):

LINE

Input 2.0 mV,

x 483(H)

440(W)

(46.4

ke

2l

100V.50/60
120V,60

Hz
2201240V,50
1 lO | 120 | 220

impedance

70 mV

impedance

x 256(D)

lbs)

Hz for JPN
for US

Hz for

24 0V, 5 0/60

I

ips)

ips)

t6%)

lhan

19 cm/s

at 19

45500

at 9.5 cm/s

45500

cm/s using

cm/s

cm/s using

cm/s using

at 9.5

cmls

45500

1,000 Hz)

Hz)

1,000

Hz)

1,000

Heads,

for capstan
than

Less

(1,800

ft.) TaPe

VU)

more

mV

impedance:

l0 kohms,

mm,

& Canada

Europe, UK

Hz internally

cm/s

Two

r1.5%

than

100

system

cm/s

using

GX

Drive

20 kohms

600

kohms

O

(17.4

and

Tape

WR

WR Tape

Tape

LN

Tape

LN

Playback

Two

ohms

t

0.3V
x 10.1")

x 19'0

Australia

switchable

Heads, Two

AC Eddy

for other

Erase

current

countries

Heads

Motors

for Reel

Drive

*

Specifications

*

improvement'purposes'

For

determined with

specifications

LN-150-7 or SCOTCH #21

Akai

and design

are subject

1 tape unless

to change

without

otherwise

notice.

noted.

4

II. DISMANTLING

OF UNIT

In
in reverse

of trouble, etc. necessitating

case

order.

dismantling,

please

dismantle

6

in

the order shown in the

photographs.

Reassemble

SCREWS A ffML KrcBS

)

III.

CONTROLS

1. PITCH

2.

3. BUILT-IN

4.

5. PINCH

CONTROL

SUPPLY REEL TABLE

REEL RETAINER

LEFT

TENSION ARM

ROLLER

6. RECORDING MUTE
7, REEL

8. REVERSE

9. POWER

10.

11.

12.
13,

14.

15. HEADPHONE

16.

SIZE SELECTOR

SELECTOR

SWITCH

VU METER

VU METER

(Right)
(Left}

TAPE SELECTOR

TAPE

TIMER

SPEED

START

SELECTOR

JACK

OUTPUT

LEVEL CONTROL

(Left}

SWITCH

(REC

MUTE)/TIMING

LAMP

Fig. I

17. MONITOR SWITCH

18. REAL TIME

19.

TAKE-UP

20. BUILT-lN REEL RETAINER

21. RIGHT TENSION ARM
HEAD

22.

23. RECORDING

24. PAUSE INDICATOR

25. REVERSE DIBECTION/STAND

26. FORWARD DIRECTION/STAND

27. MODE BUTTONS
MICROPHONE INPUT

28.

29. MEMORY MARKERS

30. LINE INPUT CONTROLS
MICROPHONE JACKS

31.

32. RECORDING

COUNTER

REEL TABLE

COVER

INDICATOR LAMP

MODE

and RESET

(Risht)

LAMP

CONTROLS

(Left/Right)

SWITCH

Controls

BUTTON

INDICATOR

BY

BY INDICATOR LAMP

LAMP

IV. PRINCIPAL PARTS LOCATION

SWITCH

MICRO

BRAKE

sw906

PLUNGER SL9O3

BRAKE

RNCH ROLLER

PLUNGER SL9O2

PLUNGER SL9O4

PAJSE

TENSION

ARM(L}

REC MUTE SWITCH

REEL SIZE S1,VITCH SW9O3

REVERSE SELECTOR SWITCH

POWER SWTTCH SW90l

SW9O4

",n,.**

{.

OIJTPUT LEVEL CONTROL

PHONES JACK

VOLUME

MONITOR SWITCH

TAPE SPEED SWITCH

IIMER START SWITCH

LR

REC MOOE SWITCH
TAPE SELECTOR SWITCH

PIÍCH

CONTROL

VR9OI

TIME

REAL

TENSION

HEAD

OPERATION ELOCK

REC

MIC
rrrup

COUNÍER

ARM

BLOCK

INOICATOR

MODE

r

RÊc

l-

J VOLUME

Fig.2 Front

VOLUME

(R)

LEVEL

J

View

REEL

MOTOR

M902 24XO-TD

RIGHT

REMO,CON JACK J9O5

VOLTAGE

SELECTOR

FUSE

TH-20rro

PC

BOARD

OPERATION

OPERATION P.C

TH-2041

ÍH-2042

VOLUME

TH-5002

P,C

PC

BOARO

BOARO

BGRD

SYS.CON PC

CAPSTAN MOTOR
M903

PRE

TH-rOr5

SCM-200

AMP PC

TH-500r4

BOARD

BOARD

Fie. 3 Rear View

V. CIRCUIT

OPERATING

PRINCIPLES

1. SYSTEM

CONTROL OPERATION

NOT
CIRCUIT

NAND
CIRCUIT

NOR
CIRCUIT

SYMBOL

X=A

X=AE

X=A+B

TRUTH

F-tfit

loll

I'IFI

TABLE

rl

LEVEL

LOW

O=

HIGH LEVEL

I:

J

Chart-1

J

10

0

I

ll

tl

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MODE

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STOP

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Schematic-2

FWD-PLAYMODE

I

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FWD-REC MODE

I

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!:

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uï

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Schematic-5

REV-REC

MODE

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FF MODE

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Schematic-7

RWD MODE

17

I-I. CIRCUIT CONSTRUCTION

The design
REC,
its input
with

oi M54410P

FF, RWD,

terminals. GX-635D

FWD in

place
PLAY. Pause is controlled
separate

l)

IC.

Block Diagram

until now

PAUSE and

PAUSE

of

by a

ICI M544IOP

OF

trad STOP,

preventing

REC

circuit

REV in

and

flip flop with

pt-nY.

AR as

is

constructed

place

of

a

ST

T

I
I

)

I

--'l

4.,
\)7

I
I
I

'--

FAST

FF

/.

1

@

Fig. 4

I

M544l0P

l8

Terminals

2)

and

their

functions

Operation

input

terminals

Control

Output

terminals

Operation

3)

Terminal

terminal AR

input

activated

Name

STOP

FF

RWD

FWD

REV

REC-

FAST

FF

F}VD

REV

REC

by each

lnput terminal
Input terminal
Input terminal
Input
Input terminal
Input
Input terminal
Terminal
Terminal
Terminal
Terminal
Terminal

input

for

stopping
for fast
for rewind

with
with

with
with
with

for
for

for

"H"
"H"
"H"
"H"
"H"

terminal

terminal for recording

forward

playback in the

playback in

preventing recording

output

signal

output during

signal

output

signal

output

signal

output

signal

Terminal
operation

forward direction

the reverse

during

during
during
during

Function

direction

forward or rewind

fast
fast forward mode

forward
reverse
recording

playback

playback mode

or

mode

mode

REC/Pause mode

Chart-2

lnpul

STOF

REC/FWD

REE/REV

NOTES:

Signal

FF

RWD

FWD

REV

1. The

2. The

3. AR
When

4.

5. At the

FAST

L
H
H
L
L
L
L

input signal

is maintained

output

control

is a

"L"

=

AR

moment

FF

L
H
L
L
L
L
L

is activated

input terminal

signal

power

the

by

until

is supplied

is on,

Output

fall

the

the next

the REC

and

during

all output

FWD

L
L
L
H
L
H
L

_]-f

of

.

input signal.

output

REC output

the

will be

REV

L
L
L
L
H
L
H

is not

"L"

"H"
is

and

REC

L
L

L

L
L
H
H

when

"H",

REC

the Stop

AR

output

mode

becomes

will be

Mode

STOP

FF Mode

Mode

RWD

Mode

FWD

Mode

REV

"L".

Mode

Output

REC/FWD
REC/REV

effected.

Mode

Mode

Chart-3

Regarding

4)
Previously

first terminal
terminal

pLly

is used

Consequently,
(FWD)

the input

M54410P

was

PAUSE

was

gÍounding

not allow

will

circuit's diode

been so

has

FLAY input

input. But

for REV

the modes

and

only

Dl3

designed

and

in

PAUSE

6th terminal

the

to be

the

that

the sixth

GX-635D,

for FWD.

changed

directly
reason,
through
addition,
both
designed

from

the first

diode

F\tD and

to take

FF or RWD

if there

even

terminal

Dl3

prioritY.

(ngVt

releasing

are simultaneous

REV,

FWD

to

FF

mode

FWD.

also

is

and

For this

grounded

RWD.

into

inputs

output

In

is

t9

VELOCITY + PULSE

WIDTH

r\

501

@

CONVERSION

Fig.5

Block

Diagram

PREVENTING CLICK

CIRCUIT

I-2.

l) When

recording must

circuit
recorded. Also when
Final Mute must operate
circuit ceases to operate
recorded.
from
In

2)
to TR28

ON.
Amp

operating
head and

When the

3)
stand-by,
base
turned ON.
potential is not supplied
is
operate
Since
electric
and

Because
fier
is
TR20 and

4)
and
When the
the
become lower than the

and
current thereby
turned
(Stop-)
This releases
and
This operation takes

circuit
out.

FOR

power

the

is in full operation

This

being recorded.

ordinary

Therefore,

only while C42

turned off. Consequently

R90.

circuit

avoided.

for

charging

turns ON. TR2l

the stop mode

recording, base

base through

P.C Board) connected

to

supply

the recording mode

power

base electric current

When

Rec head

and

turns off

TR27

current

relay

in

is

TR2l

this reason C32 and C33 are

power

on, C32

becomes

the deck

stops and

DURING

is turned

take

circuit

Rec Final

is turned ON

flows

RLI function

complete

is OFF during

is turned off

voltage on C33

and is turned
is discharged, and

ground

is effected.

therefore the click

TIMER

on for timer

place

after

else

or

power

the

before

oÍ else click

prevents

electric

R89 and

Mute relay

to TR28 collector

the signals

is effected.

is supplied

is being charged

TR27 is turned

to TR28

relay

is not supplied

C42

once

to TR28 base

only after

operation,

in this condition,

emitter in electric

is

supplied with

also

potential

from the recording

place

before

NOISE

RECORDING

recording,

the amplifier

will be

noise

click
is turned off,

the

noise

such click

cuÍrent

R90, and TR28

to the recording

timer recording

at

and

ON,

base

RLI does

with a signal.

is

charged,

through

the click

recording mode

charged.

TR20 base

on. When

ICI terminal 2

through D24.

the amplifier

noise is cut

Rec

amplifier

will be

noise

flows

RLI

@re

TR27

to

TR27

electric

and TR28

base
R89

the ampli-

noise

potential

electric

TR21

mode

not

by

will

2.THF. SAMPLE
SERVO

signals

Servo

l)

the number
either as

The motor

tions.
frequency deviation

of the

etc.,

drive circuit

motor

sion.

pulse

is

is

is

is

This

deviations
deviation

held at

is
pulse,

and
circuit.
Meanwhile,
because 112
rotation, time
the

Sample
reduced compared
deflection
For the reasons above,
to

motor

perature,
In addition,

voltage

voltage holding circuit,
voltage has

smooth
of wow

AND HOLD SYSTEM

MOTOR

of revolutions

frequency

width

in the number

is detected,

that voltage

then impressed

since

detection

revolutions,
and fewer

holding circuit,

been sharply

and stable

flutter.

&

(SCM-200)

generally created

deviations

employed

unaffected

load circuit

through

proportionately to

varies

of

converted

until

it requires

pulse

constants

and

due

generated for each

are

of circuits

Hold

circuit

the conventional

to

system.

it

minimum

chances

to the

ripple content
ripple

transport

tape

OPERATION

proportionately to

of the motor

or voltage
in
by time constants,

input signal

as

pulse

motor rotations.

to a voltage

the next servo

into

a holding

features

faulty mechanism.

of

inclusion

content of

reduced

are

GX-635D

width conver-

the motor drive

circuit

coming

can be

quick response

influence

of the

of

to result

with a minimum

shown

deflec-

uses

to the

the

The

value,

signal

and

motor

before

greatly

voltage

tem-

by

servo
the servo
the servo

in a

L|l

20

3-3/4

+7-l/2

R4 220

t5 2,?K

e

Í

-

TR4

ÍsERVo

I
9l

!

ourPUn

lx

t-

9;

*l

cro ooilí

.-r--

:+

_2

.E

INPUT

FG

SIGNAL

ó

r.

\:

TR5

=lÈ

É

lo

lrRro *

(

/á

=[

tn

ró

3

x

I

t:

I

:

TR12

CtA

t/tOO

E

K

T_

I

in

L__

TR13

---1

r.
trt

__J

I

I

t

I

O

'_.\

ÍR6

\

a8.

",

3:

TR7

(

IR€

(

;

q

9

i

rK8

lprrrclrJoNrRoll

Át

\j

-O-

AADE

D9

qE

ry

L

I

MoToE

FÀPSTAN

Fig. 6

(d)

TR8

(e)

TRB

(Í)

TR9

(9)

rRlO

(h)

TRrl

(r)TRl2

(j)

TR12

BASE

COLLECTOR

COLLECTOR

BASE

COLLECTOR

i'

1_i*

^l t

uJ-

__L

THRESHOLD

LEVEL

Fis.7

2l