Akai GX-225D User manual

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2

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:

PART

SUSTEY

MODEL

GX-225D

MODEL

GX-221

STEREO

TAPE

DECK

°

MODEL

GX-225D

.

ALSO

APPLICABLE

TO

MODEL

GX-221

STEREO

TAPE

.

RECORDER

AND

GX-221D

STEREO

TAPE

DECK

SECTION

1

SERVICEMANUAL

........-.6-¢2

20

eee

3

SECTION

2

PARTSLIST

...........

ia

aesesets.

4s

fs

6

ase

SECTION

3.

SCHEMATIC

DIAGRAM

........-.--.+.---60

_

*

<

F

SECTION

1

SERVICE

MANUAL

TABLE

OF

CONTENTS

SPECIFICATIONS

2.000

cc

ccc

ee

center

te

eee

eee

eens

4

MEASURING

METHOD

......0000

cc

cece

e

cee

cere

creer

ee

ene

ee

aeeee

6

1.

TAPE

SPEED

DEVIATION

1.0...

00

ccc

ee

eee

eee

eee

eens

6

+

WOW

AND

FLUTTER

..

ox

ccc

pba

ecw

dane

a

a

ae

wo

we

Re

ae

ee

Oe

6

3,

FREQUENCY

RESPONSE

....-

0.0

ce

ete

eee

erence

etes

6

4

RICNAL

TO

NOISE

RATIO

\-soidw

doo

poh

oe

OR

eo

a

ee

Oe

6

5.

TOTAL

HARMONIC

DISTORTION

FACTOR

....-0..00

0000

eee

eer

tee

7

6.

CROSS

TALK

(Cross

talk

between

the

channels)

.

06-66

0

ee

eee

ee

es

q

@

ERASE

RATIO“

|

cect

6's

289

6S

Uk

OE

Ne

eS

TS

Oi we

eS

7

8.

POWER

OUTPUT

.....

bi

an

seg

this

duds

wee

bie

ut

RUE

ec

OHS

AR

VCE

ERAGE

SD

2

7

DISMANTLING

OF

UNIT

.......000

00

cece

cece

eee

ete

eet

eeees

‘eee

B

-

TRANSPORT MECHANISM

...-.-0-

00000

eect

e

eee

eee

ete

eee

ee

eens

10

if

FORWARD

PLAYBACK

RECORDING

MODE

......

Pe

er

ee

ee

ae

it

.

FAST

FORWARD/REWIND

MODE

......-

20sec

eee

ere

ee

teeters

11

:

BLOCK

DIAGRAM

OF

VOLTAGE

SUPPLY

CIRCUIT

TO

MOTOR

AT

EACH

MODE

....

!1

4.

SYSTEM

CONTROL

CIRCUIT

OPERATION

,..

0.2000

eee

eee

ee

eee

13

MECHANISM

ADJUSTMENTS

........-0

0-0-0

ee

eee

eee

cereeee

Sid

Sore

eee

14

1.

REEL

TABLE

HEIGHT

ADJUSTMENT

..

0.0...

0s

eee

eee

eee

eee

ets

14

2,

PINCH

WHEEL

PRESSURE

MEASURING

METHOD

Aiki

ated

rks

he

eine

bee

14

3.

BRAKE

TENSION

ADJUSTMENT

..

2.0.0

eee

ee

eter

eres

15

4,

SUPPLY

VOLTAGE

AND

TENSION

AT

VARIOUS

OPERATING

MODES

......----

15

HEAD

ADJUSTMENTS

.......

sos

se

ttn

od

athchv

a

du

Ns

fet

desc

Goad:

Saal

oS

taass

teh

16

1.

HEAD

HEIGHT

ADJUSTMENT

.......

0.0002

te

eee

reese

BAG

Parity

arg

ites

anette

16

2,

HEAD

AZIMUTH

ALIGNMENT

ADJUSTMENT

....

26-02

-

seer

ees

17

AMPLIFIER

ADJUSTMENTS

1.0.0.0

00

cece

ee

teeter

eee

eee

18°

1.

PLAYBACK

OUTPUT

LEVEL

ADJUSTMENT

......000

00

ee

eee

eee

rece

ree

18

3.

VU

METER

SENSITIVITY

ADJUSTMENT

.....

St

dnokudiend

upesoe

ata

peated

18

3.

HIGH

RANGE

VARIATION

CHECK

2.0.0.0

2.

cee

eee

et

eet

nneee

18

4.

RECORDING

LEVEL

ADJUSTMENT

..........

Bacio

Gaerne

ein

Aiae

&

Bitte

Bushs

21

5.

RECORDING

BIAS

FREQUENCY

MEASURING

METHOD

.........--

2022s

2

6.

RECORDING

BIAS

VOLTAGE

ADJUSTMENT

(Frequency

Response

Adjustment)

.-....-

21

_

AUTOMATIC

NOISE

REDUCTION

AMPLIFIER

ADJUSTMENTS

(GX-225D)

......-+++22

i

AN

RAMP:

ADTUSTMENT

6a.

as-eGice

XS

So

hae

ae

Sed

a

SES

Si

are

Ee

Be

22

‘>.

A.N.R.

OPERATION

AND

CHARACTERISTICS

...-...---00-035

Bie

phan

Readers

23

COMPOSITE

VIEWS

OF

COMPONENTS

.....

2-22-02

e

ete

rece

rts

tte

24

i.

SPECIFICATIONS

An

asterisk

next

to

a

figure

indicates

the

minimum

guaranteed

performance.

TRACK

SYSTEM

REEL

CAPACITY

TAPE

SPEED

WOW

AND

FLUTTER

FREQUENCY

RESPONSE

AKAIS.R.T.

Tape

Regular

Tape

SIGNAL

TO

NOISE

RATIO

'

HUM

AND

NOISE

DISTORTION

FACTOR

TONE

CONTROLS

Treble

Bass

CROSS

TALK

ERASE

RATIO

BIAS

FREQUENCY

BIAS

LEAK

HIGH

FREQUENCY

DEVIATION

Between

Channels

Between

FWD/REV

REC./P.B.

LEVEL

|

INPUTS

Mic

Input

Line

Input

.

Din

Input.

_

OUTPUTS

Line

Output

Din

Output

Speaker

Output

HEAD

PHONE

OUTPUT

REVERSING

TIME

FAST

FORWARD

AND

REWIND

TIME

MOTORS

Main

Motor

"

Reel

Motor

Erase

Head

4

track

2

channel

stereo/monaural

system

Up

to

7”

reel

7-1/2

ips(19

cm/sec.)

+0.7%(*+0.8%)

3-3/4

ips(9.5

cm/sec.)

£0.7%(*£0.8%)

1-7/8

ips(4.75

cm/sec.)

+0.7%(*4£0.8%)

Less

than

0.089%{*0.12%)

R.M.S,

at

7-1/2

ips

_

Less

than

0.12%

*0,25%)

R.M.S.

at

3-3/4

ips

Less

than

0,20%(*0.4%)

R.M.S,

at

1-7/8

ips

30

to

25,000

Hz

+3

dB

at

7-1/2

ips

30

to

20,000

Hz

+3

dB

at

3-3/4

ips

30

to

10,000

Hz

£3

dB

at

1-7/8

ips

30

to

23,060

Hz(*36

to

22,000

Hz}

+3

dB

at

7-1/2

ips

30

to

19,000

Hz(*38

to

18,000

Hz)

+3

dB

at

3-3/4

ips

30

to

9,000

Hz(*40

to

9,000

Hz)

+3

dB

at

1-7/8

ips

Better

than

50

dB(S3

dB

with

N.R.

process)

*

Better

than

48

dB

at

7-1/2

ips

*

Better

than

47

dB

at

3-3/4

ips

*

Better

than

45

dB

at

1-7/8

ips

*

Better

than

44

dB

at

Reverse

Mode

§

mV

Tone

Control

and

Main

Volume:

Min.

(Model

GX-221

only)

Less

than

1.5%{*3%)

at

1,000

Hz

“0”

VU

Recording

12 +2

dB(Max.)

and

—14

+2

dB(Min.)

at

10

kHz

12

+2

dB(Max.)

and

-10

+2

dB{Min.}

at

100

Hz

(Model

GX-221

only)

Better

than

65

dB(*58

4B)

monaural

Better

than

50

dB(*43

dB)

stereo

Better

than

70

dB

100

kHz

2

5%

Less

than

—20

VU

Within

2

dB,

using

an

8,006

Hz

3-3/4

ips

recorded

tape

at

7-1/2

ips

Within

3

dB,

using

an

8,000

Hz

3-3/4

ips

recorded

tape

at

7-1/2

ips

441.5

dB

0.2

m¥{*0.4

mV)

Impedance:

10

kQ

50

mV(*60

m¥)

Impedance:

150

kQ

2

mV(low)

and

50

mV{*60

mV}

(high)

1,228V

(4+

1dB)}

Impedance:

20kQ

0.4V

30

W

total

music

power

at

89

(GX-221

only)

20

W

continuous

power

at

82

{GX-221

only)

30

to

40

mV

at

82

2

to

6

sec.

85/65

sec.,

using

a

1,200

ft.

tape

at

50/60 Hz

3

speed

hysteresis

synchronous

motor

Type:

HC-16X

=

oh

Revolutions:

3,000/1,500/750

r.p.m.(50

Hz)

3,600/1,800/900

r.p.m.(60

Hz)

Two

6-pole

eddy

current

outer

rotor

motors

Type:

24X0-MR

Revolutions:

930

r.p.m.

(50

Hz)

1,120

r.p.m.

(60

Hz)

Type:

E4-250

Gap:

0.6

mm

Impedance;

1952

+

10%

at

100

kHz.

D.C.

Resistance:

3.52

ions

Recording

Head

Playback

Head

TRANSISTORS

Type:

R4-200

Gap:

44

+

15%

Impedance:

1,8702

at

100

kHz

D.C.

Resistance:

82

Type:

P4-200

Gap:

1,75y

15%

Impedance:

3

4

1k

at

1

kHz

D.C.

Resistance:

5002

LD3141.,.2

28C372(Y}

...1

28C871(F)..,12

28C945(Q)(R)...6

28C968(3}(4)

-..3

28C458LG(C)...6

STKOLS

...

2(GX-221

only)

28C971(2)(3)

RED...

2

28C1211(C}(D)

,

..

1

2SD223(G)(Y)..-

1

2SCTLICE)...4

DIODES

(N.R.

Amp.)

(N.R.

Amp.)

IN34A...7

5B2...1(GX-221

only)

10D1...3

WZ-240.,.1

lop4...1

WG-599

...

4(N.R.

Amp.}

POWER

SUPPLY

100

to

240

V

A.C.

50/60 Hz

POWER

CONSUMPTION

INSULATION

RESISTANCE

90W

Models

GX-225D,

GX-221D

135W

Model

GX-221

Mare

than

50

M@

INSULATION

DURABILITY

DIMENSIONS

WEIGHT

500V

D.C.

for

more

than

1

min.

duration,

430(W)

x

425(H)

x

230(D)

mm

(17.2"

x

17”

x

9.2")

20.5

kg(45.1

Ibs.)

Models

GX-225D,

GX-221D

22.5

kg(49.5

Ibs.)

Model

GX-221

NOTE:

Specifications

subject

to

change

without

notice.

ll.

MEASURING

METHOD

1,

TAPE

SPEED

DEVIATION

Frequency

counter

input

GX-225D

Line

output

Fig.

1

As

shown

in

Fig.

1,

connect

a

Frequency

Counter

to

the

Line

output.

Playback

a

1,000

Hz

pre-recorded

test

tape.

Take

a

frequency

counter

reading

at

the

beginning,

middle,

and

end

of

tape

winding

during

playback.

The

maximum

value

of

these

respective

readings

will

represent

tape

speed

deviation.

2.

WOW

AND

FLUTTER

GX-225D

Wow

and

Flutter

Line

output

Meter

input

Fig.

2

Method

A

As

shown

in

Fig.

2,

connect

the

Line

output

to

the

Input

of

a

Wow

and

Flutter

Meter.

Playback

a

3,000

Hz

pre-recorded

test

tape

and

take

a

wow

and

flutter

meter

reading

at

the

beginning,

middle,

and

end

of

tape

winding.

The

maximum

yalue

of

these

respective

readings

will

represent

the

wow

and

flutter.

Method

B

Supply

a

3,000

Hz

sine

wave

signal

from

an

Audio

Frequency

Oscillator

and

make

a

recording

on

a

blank

tape

at

the

beginning,

middle,

and end

of

tape

winding.

Rewind

and

playback

the

resultant

signal.

Measure

wow

and

flutter

with

a

Wow

and

Flutter

Meter.

(The

wow

and

flutter

value

of

Method

B

will

be

close

to

twice

that

of

Method

A.)

3,

FREQUENCY

RESPONSE

GX-225D

Line

Frequency

input

ane

Oscillator

ae

8

output

High

Sensitivity

V.T.V.M,

Fig,

3.

For

measuring

frequency

response,

connect

instru-

ments

as

shown

in

Fig.

3

and

proceed

as

follows:

1)

Supply

a

1,000

Hz

sine

wave

to

the

Line

input

from

an

Audio

Frequency

Oscillator

through’

an

Attenuator.

2)

Set

recorder

to

recording

mode

and

turn

recording

level

contro!

volume

and

line

output

level

control

volume

to

maximum,

Adjust

attenuator

to

obtain

a+4

dB

V.T.V.M.

reading.

3)

Under

conditions

described

in

2)

above,

re-adjust

attenuator

so

that

the

Line

Output

is

—16

dB,

and

record

30

to

22,000Hz

at

7-1/2

ips

spot

fre-

quencies.

4)

Rewind

the

tape

and

playback

from

the

beginning.

Take

V.T.V.M.

spot

frequency

readings

and

plot

values

on

a

graph.

.

NOTE:

When

measuring

frequency

response,

new

tape

should

be

used.

4,

SIGNAL

TO

NOISE

RATIO

GX-225D

High

Sensitivity

Line

output

VIVM,

Fig.

4

As

shown

in

Fig.4,

connect

a

High

Sensitivity

V.T.VM.

to

the

Line

output.

Playback

a

250

Hz

“Q”

VU

pre-recorded

test

tape

and

mieasure

the

output.

Then

remove

the

tape

and

measure

the

noise

level

under

the

same

condition,

Convert

each

of

the

measured

values

into

decibels.

-

§,

TOTAL

HARMONIC

DISTORTION

GX-225D

Line

input

—Line

output

Audio

Frequency

Oscillator

Distortion

Meter

Fig.

5

Connect

the

measuring

instruments

as

shown

in

Fig.

5

and

record

a

1,000

Hz

sine

wave

signal

at

“0”

VU.

Playback

the

resultant

signal

and

measure

the

overall

distortion

factor.

Measure

the

noise

level

of

the

tape

recorder

without

the

tape.

Connect

the

audio

fre-

quency

oscillator

directly

to

the

distortion

meter

for

measurement

of

the

distortion

factor

of

the

oscil-

lator.

The

required

distortion

factor

can

be

obtained

from

the

results

of

the

above

measurement

by

the

following

formula:

do

=d—di

—d2

where,

do

=

Required

distortion

factor

d

=

Overall

distortion

factor

di

=

Noise

level

d2

=

Distortion

factor

of

the

oscillator

NOTE:

When

measuring

the

distortion

factor,

new

’

tape

should

be

used.

6.

CROSS

TALK

|

(Cross

talk

between

the

channels}

(TAPE)

REV

oy

Se

ees

GS

TAPE

DIRECTION

Fig.

6

As

shown

in

Fig.

6,

first

record

a

1,000

Hz

sine

wave

signal

on

Track

No.

3

at

+3

VU

level.

Next,

record

under

a

non-input

condition.

Then,

playback

the

tape

on

Tracks

No.

3

and

4

(reversed

condition

of

tape)

through

the

B.P.F,

(band

pass

filter

sensitivity

...

1:1)

and

obtain

a

ratio.

between

the

two

from

the

following

formula:

,

Eo

E2—-E1

where,

C

=

Desired

cross

talk

ratio

(dB)

Bo

=

1,000

Hz

signal

output

level

[i

’

Be

=

1,000

Hz

cross

talk

level

Ei

=Non-input

signal

recorded

level

Bax

'C

=

20

log

(dB)

7.

ERASE

RATIO

As

shown

in

Fig.4,

connect

a

High

Sensitivity

V.T.V.M.

to

the

Line

ouput.

Playback

a

virgin

tape

and

take

a

V.T.V.M.

reading

of

the

output

level.

Next,

record

a

1,000

Hz

sine

wave

signal

at

+3

VU,

‘then

playback

this

recorded

signal

and

take

a

V.T.V.M.,

reading

of

the

output

level.

Next,

using

this

pre-recorded

tape,

record

under

a

non-input

condi-

tion

and

take

a

reading

of

the

noise

level

output

of

the

erased

signal

and

obtain

a

ratio

between

the

two

from

the

following

formula:

Eo

Er

=

20

log

(dB)

E2-E1

where,

Er

=

Desired

erase

ratio

(dB)

Eo

=

1,000

Hz

signal

output

level

Ez

=

Non-input

signal

recorded

level

Ex

=

Virgin

tape

noise

output

level

8.

POWER

OUTPUT

(GX-221

only)

High

Sensitivity

output

V.T.VM.

Fig.

8

As

shown

in

Fig.

7,

connect

an

89

dummy

load

resistor

to

the

speaker

output

and

connect

this

terminal

to

a

High

Sensitivity

V.T.V.M.

Playback

a

250Hz

“0”

VU

pre-recorded

test

tape

and

take

a

V.T.V.M.

reading

of

the

output

level.

The

resultant

output

can

be

obtained

from

the

above

measurement

by

using

the

following

formula:

al

-2

P=

Ww)

where,

P

=

Desired

power

output

(watts)

E

=

Measured

voltage

(R.M.S.)

R=

8&Q

Il.

DISMANTLING

OF

UNIT

In

case

of

trouble,

etc.

necessitating

disassembly,

please

disassemble

in

the

order

shown

in

photographs.

Reas-

semble

in

reverse

order.

SIDE

PLATE

h

REAR

PLATE

MECH.

BLOCK

&

MECHANISM

ADJUSTMENT

LOWER

FRAME

cena

-

P.B.

AMP.

P.C.

BOARD

REC.

AMP.

P.C.

BOARD

CARD

HOLDER

7

SCREWS

IV.

TRANSPORT

MECHANISM

Fig.

10

F.FWD/RWD

MODE

10