Akai Gx-2800d-ss User manual

SERVICE

MANUAL

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X-280D-SS

SECTION

1

SERVICEMANUAL

...........---020004-

3

SECTION2

PARTSLIST

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SECTION

3

SCHEMATIC

DIAGRAM

.............+++++

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VI.

VII.

VIII.

SECTION

1

SERVICE

MANUAL

§

TABLE

OF

CONTENTS

SPECIFICATIONS

......

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PAR

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4

MEASURING

METHOD

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6

1.

TAPE

SPEED

DEVIATION

.....-

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6

2.

WOW

AND

FLUTTER

...

1...

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teeter

eens

6

3,

FREQUENCY

RESPONSE

........+6-

a

olka

de

Wale

Rare

en

we

erence

a

bb

To

©

ere!

See

ee

8

6

4,

SIGNAL

TO

NOISE

RATIO

.........-

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terse

ap

Some

Bien

BSE:

OES ate

vault

a

Sea

aa

Youle

Surges

te

Oe

6

5.

TOTAL

HARMONIC

DISTORTION

......-

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See

7

6.

CROSS

TALK.

esos

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egie

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Ge

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bes

Owe

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Regd

eed

ON

te

gb

AE

RTO

Oy

we

7

DISMANTLING

OF

UNIT

.......

2...

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8

MECHANISM

ADJUSTMENTS

.........

0.

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eer

tere

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10

1,

TAPE

SPEED

ADJUSTMENT

(Servo

Control

Amp.

Adjustment)...........6.-

...

10

2,

DIRECT

FUNCTION

TIME

CONSTANT

ADJUSTMENT

.,..

2...

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es

10

3.

BRAKE

TENSION

ADJUSTMENT

....

2.0.0...

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ees

11

4,

SUPPLY

VOLTAGE

TO

BOTH

TORQUE

MOTORS

AS

WELL

AS

TENSION

AT

‘

VARIOUS

OPERATING

MODES....

12

5.

REEL

TABLE

HEIGHT

ADJUSTMENT

.....

0...

ccc

e

cece

n

eee

eens

12

6.

PINCH

WHEEL

PRESSURE

MEASUREMENT

AND

ADJUSTMENT

ep

Biwi

eS

alsaalene

..

13

HEAD

ADJUSTMENTS

......

Gib

ob

RRO

Ble

Braise.

Fa

Roe

pate

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84

Sip

oat

eama

eared

14

I.

HEAD

CONSTRUCTION

...........

000-0

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senerte,

Suktete

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sactcy'é

14

2:

ORDER:OF

HEADS

(oc

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sei

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orcas

oy

OORT,

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aed

edo

14

3.

HEAD

HEIGHT

ADJUSTMENT

.....

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14

4,

HEAD

AZIMUTH

ALIGNMENT

.........

0.

eee

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tees

15

AMPLIFIER

ADJUSTMENTS

......

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Salad

Winter

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Sees

16

1,

PLAYBACK

OUTPUT

LEVEL

ADJUSTMENT

.......

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16

2.

VU

METER

SENSITIVITY

ADJUSTMENT

.........

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16

3.

RECORDING

LEVEL

ADJUSTMENT

........

2.

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19

4,

RECORDING

BIAS

FREQUENCY

MEASURING

METHOD

AND

ADJUSTMENT

.....

19

5.

RECORDING

BIAS

VOLTAGE

ADJUSTMENT

(Frequency

Response

Adjustment)

.

19

6.

4-CHANNEL

PHASE

CHECK

......

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TRANSPORT

MECHANISM

..........

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22

1,

FROM

STOP

TO

FORWARD

PLAYBACK

....

2...

0

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rene

24

2.

2-CHANNEL

AUTOMATIC

REVERSE

PLAYBACK

....

0.

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nee

24

3..

FAST

FORWARD

©

fictiice

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a

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ele

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lenaeere

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ate

ee

eee

we

SEE

WEE

24

4,

REWIND

.............

ey

an

Sarena

alana

ae

ate

t

al

sada

oidivtncah,

Cubes

ds

GU

owes

eeiat

Bibs

soho)

soeie

toe

24

5,

4-CHANNEL

REPEAT

CIRCUIT

..

0...

2...

cece

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25

SERVO

MOTOR

OPERATING

PRINCIPLES

......

0...

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26

COMPOSITE

VIEWS

OF

COMPONENTS

.........--

2

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|

I.

SPECIFICATIONS

a

An

asterisk

a

figure

indicates

the

minimum

guaranteed

performance.

TRACK

SYSTEM

4-track

4-channel/2-channel

compatible

stereo

system

REEL

CAPACITY

Up

to

7’

reel

TAPE

SPEED

WOW

AND

FLUTTER

7-1/2

ips

(19

cm/sec.)

+

0.5%

(**

1u%)

3-3/4

ips

(9.5

cm/sec.)

+

0.5%

(*+1.0%)

Less

than

0.10%

(*0.12%)

R.MLS.

at

7-1/2

ips

Less

than

0.15%

(*0.18%)

R.M.S.

at

3-3/4

ips

FREQUENCY

RESPONSE

Low

Noise

Tape

Regular

Tape

20

to

25,000

Hz

(*30

to

24,000

Hz

)

+3

dB

at

7-1/2

ips

30

to

20,000

Hz

(*30

to

15,000

Hz

)

+3

dB

at

3-3/4

ips

30

to

23,000

Hz

(*30

to

22,000

Hz

)

+3

dB

at

7-1/2

ips

30

to

19,000

Hz

(*30

to

13,000

Hz

)

+3

dB

at

3-3/4

ips

SIGNAL

TO

NOISE

RATIO

Better

than

55

dB

*Better

than

48

dB

at

7-1/2

ips

*Better

than

46

dB

at

3-3/4

ips

DISTORTION

FACTOR

0.8%

at

1,000

Hz

“0”

VU

recording

*Less

than

2%

at

7-1/2

ips,

1,000

Hz

“0”

VU

recording

*Less

than

3%

at

3-3/4

ips,

1,000

Hz

“0”

VU

recording

CROSS

TALK

Better

than

45

dB

2-channel

stereo

Better

than

40

dB

4-channel

stereo

ERASE

RATIO

Better

than

70

dB

BIAS

FREQUENCY

100

to

110

kHz

BIAS

LEAK

Less

than

—20

VU

HIGH

FREQUENCY

DEVIATION

Between

channels

Between

FWD

&

REV

Within

3

dB,

using

a

8,000

Hz

at

3-3/4

ips

recorded

tape

Within

4

dB,

using

a

8,000

Hz

at

3-3/4

ips

recorded

tape

0.5mV_

Impedance:

10

kQ

100

mV_

Impedance:

150

kQ

10

mV

(Low)

and

60

mV

(High)

1.228V

(4

+1.5

dB)

Impedance:

25

kQ

0.4V

30/60

min.,

4-channel/2-channel

stereo

recording,

using

a

1,200

ft.

tape

at

7-1/2

ips

68/83

sec.,

using

a

1,200

ft.

tape

at

60/50

Hz

2-speed

servo

control

outer

rotor

motor

Type:

SCM2-24

Revolutions:

520

r.p.m.

at

7-1/2

ips

260

r.p.m.

at

3-3/4

ips

Two

6-pole

eddy

current

outer

rotor

motors

Type:

24XO-MR

Revolutions:

930

r.p.m.

at

50

Hz

1,120

r.p.m.

at

60

Hz

t

INPUTS

Mic

Input

Line

Input

Din

Input

OUTPUTS

Line

Output

Din

Output

RECORDING

CAPACITY

FAST

FORWARD

AND

REWIND

TIME

MOTORS

Capstan

Motor

Reel

Motor

HEADS

Full

Track

Erase

Head

4-track

Erase

Head

Recording

Head

Playback

Head

Type:

EF-200

Gap:

0.4mm

Impedance:

3502

+10%

at

100

kHz

D.C.

Resistance:

32

Type:

E4-250

Gap:

0.6

mm

:

Impedance:

1952

+10%

at

100

kHz

D.C.

Resistance:

3.52

Type:

R4-280

Gap:

4

micron

+15%

Impedance:

162

415%

at

1

kHz

D.C.

Resistance:

130

.

Type:

P4-280

é

Gap:

1.7

micron

+15%

Impedance:

1,346Q

at

1

kHz

D.C.

Resistance:

3502

PAT

TRANSISTORS

2SA564(R)

...

2

2SC968(2)

(3)

(4)...8°

2SC458LG(C)...

20

2SC1014(D)

(E)...1

2SC711(D)

(E) (F)

(G)...13

2SD234(Y)...2

2SC971(2)

(3)

(red)...

2

2SC945(Q)

(R)

(S)...

18

ILC.

LD-3141...4

DIODES

IN34A,..

32

10DC-1

(black)...

1

:

10D1...14

10DC-1

(red)...

1

:

10D4...3

RD9IA...1

THERMISTER

41D26...1

POWER

SUPPLY

Be

100

to

240V

A.C.

50/60

Hz

POWER

CONSUMPTION

;

140W

INSULATION

RESISTANCE

More

than

50

MQ

INSULATION

DURABILITY

500V

D.C.

for

more

than

1

min,

duration

DIMENSIONS

435(W)

x

505(H)

x

250(D)

mm

(17.4"

x

20.2”

x

10")

WEIGHT

22.4

kg

(49.5

Ibs.)

i

NOTE:

Specifications

subject

to

change

without

notice.

ll.

MEASURING

METHOD

1.

TAPE

SPEED

DEVIATION

Frequency

counter

input

GX-280D-SS

Line

output

Fig.

1

As

shown

in

Fig.

1,

connect

a

Frequency

Counter

to

the

Line

Output

of

Model

GX-280D-SS.

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-280D-SS

Wow.

and

Flutter

Line

output

Method

A

As

shown

in

Fig.

2,

connect

the

Line

Output

of

Model

GX-280D-SS

to

the

Input

of

a

Wow

and

Flut-

ter

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

value

of

these

respective

readings

will

represent

the

Wow

and

Flutter.

Method

B

-

a

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-280D-SS

Line

input

=

Line

output

Audio

Frequency

Oscillator

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

signal

to

the

Line

Input

of

Model

GX-280D-SS

from

an

Audio

Fre-

quency

Oscillator

through

an

Attenuator.

2)

Set

recorder

to

recording

mode

and

turn

recording

level

control

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,

readjust

attenuator

so

that

the

Line

Output

is

—16

dB, and

record

30

to

24,000

Hz

spot

frequencies.

4)

Rewind

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-280D-SS

High

Sensitivity

V.T.V.M.

Line

output

Fig.

4

As

shown

in

Fig.

4,

connect

a

High

Sensitivity

V.T.V.M.

to

the

Line

output

of

Model

GX-280D-

SS.

Playback

a

250

Hz

“0”

VU

pre-recorded

test

tape

and

measure

the

output.

Therh

remove

the

tape

and

measure

the

noise

level

under

the

same

condition.

Convert

each

of

the

measured

values

into

decibels,

5.

TOTAL

HARMONIC

DISTORTION

GX-280D-SS

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

oscillator.

The

required

distortion

factor

can

be

obtained

from

the

results

of

the

above

measurement

by

the

following

formula’

dy

=d—d,

—d,

where,

do

=

Required

distortion

factor

d

=

Overall

distortion

factor

d,

=

Noise

level

d,

=

Distortion

factor

of

the

oscillator

NOTE:

When

measuring

the

distortion

factor,

new

tape

should

be

used.

6.

CROSS

TALK

1)

Between

the

tracks

(2-Channel)

(TAPE)

©

@

TAPE

DIRECTION

@®

.

TAPE

DIRECTION

:

WM

Fig.

6

As

shown

in

the

figure,

first

record

a

1,000

Hz

sine

wave

on

track

No.

3

at

+3

VU

level.

Next,

remove

the

1,000

Hz

input

signal

and

record

under

a

non-input

condition.

Then,

playback

the

tape

on

tracks

3

and

|

(reversed

condition

of

tape)

through

the

1,000

Hz

B.P.F.

(Band

Pass

Filter,

Sensitivity

...

1:

1)

and

obtain

the

ratio

between

the

two

by

using

the

following

formula.

=

20

ot

(dB)

’

where,

C

=

Desired

cross

talk

ratio

(dB)

Eo

=

1,000

Hz

signal

output

level

rs

E,

=

1,000

Hz

cross

talk

output

level

E,

=

Non-input

signal

record

level

Bx@axXy

2)

Between

the

channels

(4-Channels)

OME

TAPE

DIRECTION

semewnseaige

=

z

@

Fig.

7

As

shown

in

the

figure,

first

record

a

1,000

Hz

sine

wave

on

track

No.

1

at

+3

VU

level.

Next,

remove

the

1,000

Hz

input

signal

and

record

under

a

non-input

condition.

Then,

playback

the

tape

on

track

No.

1

and

No.

2

through

the

1,000

Hz

B.P.F.

(Band

Pass

Filter,

Sensitivity

.

1:

1)

and

obtain

a

ratio

between

the

two

from

the

following

formula.

=

20

logy

-

(dB)

where,

C

=

Desired

cross

talk

ratio

(dB)

Ey

=

1,000

Hz

signal

output

level

a=

=

|

E,

=

1,000

Hz

cross

talk

output

level

=

Nox-input

signal

record.

level

RY

|

Ill.

DISMANTLING

OF

UNIT

In

case

of

trouble,

etc.

necessitating

disassembly,

please

disassemble

in

the

order

shown

in

photographs.

Reassemble

ke

in

reverse

order.

;

AMPLIFIER

KNOBS

\

CASE

BLOCK

es,

%

slightly

ts)

AMP.

PANEL

SCREWS

4

AMP,

BLOCK

\

MECH.

BLOCK

AER

reray

RETAINERS

seers

IV.

MECHANISM

ADJUSTMENTS

SERVO

CONTROL

AMP

PC.

BOARD-

LI

VI2031SC-O1

VR

202

2KB

1.

TAPE

SPEED

ADJUSTMENT

10

(Servo

Control

Amp.

Adjustment)

1)

Connect:

a

frequency

counter

to

the

Line

Out-

puts

as

shown

in

Fig.

1.

2)

Depress

3-3/4

ips

(9.5

cm/sec.)

Tape

Speed

Selec-

tor

Switch

and

playback

a

1,000

Hz

pre-recorded

test

tape.

3)

Adjust

the

core

of

coil

L1

(V1023SC-01)

shown

in

Fig.

8

to

obtain

a

frequency

counter

indica-

tion

of

500

Hz

+1%.

4)

After

the

3-3/4

ips

(9.5

cm/sec.)

tape

speed

adjustment

has

been

completed,

depress

the

7-1/2

ips

(19

cm/sec.)

Tape

Speed

Selector

Switch

and

adjust

Servo

Control

P.C.

Board

semi-fixed

resistor

VR202

(2

kB)

shown

in

Fig.

8

to

obtain

a

frequency

counter

indication

of

1,000

Hz

+1/

—0.5%.

NOTE:

When

making

tape

speed

adjustment,

it

is

necessary

to

make

the

low

speed

(3-3/4

ips)

adjustment

first.

SYSTEM

CONTROL.

PC.

BOARD

VRIO]

IOKB

VR102

IOKB

Fig.

8

2.

DIRECT

FUNCTION

TIME

CONSTANT

ADJUSTMENT

1)

FWD

@

REV

Time

Constant

Adjust

System

Control

P.C.

Board

semi-fixed

resistor

VR101

(30

kB)

shown

in

Fig.

8

so

that

when

the

machine

is

switched

from

FWD

to

REV

mode

or.

from

REV

to

FWD

mode,

the

pinch

wheel

separates

from

the

capstan

in

about

3

seconds.

2)

Adjust

System

Control

P.C.

Board

semi-fixed

resistor

VR102

(10

kB)

shown

in

Fig.

8

so

that

when

the

mackine

is

switched

from

F.FWD

or

RWD

to

FWD

or

REV

mode,

the

time

constant

is

about

1.5

seconds.

NOTE:

When

making

adjustments

outlined

in

Items

2.

1)

and

2.

2)

above,

when

the

machine

is

switched

from

the

various

modes

to

FWD

or

REV,

confirm

that

correct

capstan

motor

(servo

motor)

revolutions

are

reached

by

the

time

the

pinch

wheel

contacts

the

capstan.

te

3.

BRAKE

TENSION.

ADJUSTMENT

1)

Use

a

60

mm

diameter

tape

wound

on

a

5”

reel

and

measure

the

brake

tension

with

a

tension

gauge

as

shown

in

Fig.

9.

Ideal

tape

tension

is

350

grams.

: ,

2)

Brake

tension

adjustment

methods

are

as

follows:

(Refer

to

Fig.

10)

a.

Change

position

of

suspended

springs

(d)

(d’).

b.

Loosen

screws

(a),

(b)

as

well

as

(a’)

(b’)

and

adjust

the

vertical

(up

and

down)

position

of

spring

suspension

metal

(c)

(c’).

c.

Loosen

screws

(e).

(f)

as

well

as

(e’)

(f’)

and

adjust

the

horizontal

(left/right)

position

of

brake

band

suspension

metal

(g)

(g’).

NOTE:

In

making

brake

tension

adjustment,

con-

firm

that

when

the

machine

is

set

to

each

of

the

various

modes

(except

stop

mode)

the

brake

band

completely

separates

from

the

cloth

tape

on

the

brake

drum

(Refer

to

Fig.

11).

dbac

fge

ee

Se

ce

Pott

Tt

11

REEL

TABLE

~_

penned

aeemeeeyy

—-

.

Wedadiidhaadccadaaaacdaddaaddaaciddaddddddaidaguauiadéddidididdddadidddtadddgiasuddiacadédaidaiuaidazddcddauaauaiai«daacdadaaddadéaddaaaddiddds

a

4.

SUPPLY

VOLTAGE

TO

BOTH

TORQUE

MOTORS

AS

WELL

AS

TENSION

AT

Left

Side

"

30V

(35V)

55g

"55V

(60V)

180g

100V

(100V)

500g

11V

(43V)

15g

VARIOUS

OPERATING

MODES

Right

Side

55V

(60V)

180g

30V

(35V)

55g

11V

(13V)

15g

100V

(100V)

500g

Figures

in

parentheses

indicate

voltage

at

60

Hz.

12

Chart

1

BRAKE

DRAM

CLOTH

TAPE

BRAKE

BAND

Fig.

11

REEL

TABLE

HEIGHT

ADJUSTMENT

SCREWS

g

7

A

4

G

y

cy

¢

Fig.

12

5.

REEL

TABLE

HEIGHT

ADJUSTMENT

Loosen

the

reel

table

height

adjustment

screws

shown

in

Fig.

12

and

adjust

by

moving

the

reel

table

as

indicated

by

the

arrow

and

positioning

so

that

the

tape

winds

in

the

center

of

the

reel.

A

i)

PINCH

WHEEL

PRESSURE

SPRING

Ce)

ag

AP

PLUNGER

SOLENOID

ci

PINCH

WHEEL

ARM

a

r/

©

CAPSTAN

oO

PINCH

WHEEL

—--————--—

INDICATES

"“STOP',

"F.FWD.’

AND

"RWD,’

MODE

«

6,

PINCH

WHEEL

PRESSURE

MEASUREMENT

AND

ADJUSTMENT

Use

a

tension

gauge

and

measure

the

pinch

wheel

pressure

as

shown

in

Fig.

13.

Read

the

value

on

the

gauge

as

soon

as

the

pinch

wheel

separates

from

the

tape

and

tape

travel

stops.

Ideal

pinch

wheel

pressure

is

1.5

kg.

To

regulate

pinch

wheel

pres-

sure,

adjust

nuts

(a),

(b)

shown

in

Fig.

13.

Fig.

13

V.

HEAD

ADJUSTMENTS

1.

HEAD

CONSTRUCTION

(4

CH.)

(2

CH.)

CH.|

FRONT

LEFT

FOWARD

LEFT

CH.2

REAR

LEFT

REVERSE

RIGHT

CH.3

FRONT

RIGHT

FOWARD

RIGHT

CH4

REAR

RIGHT

REVERSE

LEFT

Fig.

14

4

Track

4

Channel/2

Channel

Head

2.

ORDER

OF

HEADS

4TRACK/2CH,

FULL

TRACK

CK/4CH.,

REC

t

ERASE

HEAD

ERASE

HEAD

REC,

HEAD

4TRACK/4CH,

P.B.

HEAD

BLK.

ORG,

R.L.

VLT.

RR.

WHT.

F.L.

RED.

GRY.

FLR.

Fig.

15

3.

HEAD

HEIGHT

ADJUSTMENT

1)

Full

Track

Erase

Head

At

playback

mode,

loosen

head

height

control

screws

(a)

(a’),

and

adjust

so

that

the

tape

is

equi-distant

in

relation

to

the

protruding

top

and

bottom

edges

of

the

full

track

erase

head

core

(width

between

top

edge

of

tape

and

top

edge

of

head

core

is

the

same

as

the

distance

between

the

bottom

edge

of

the

tape

and

the

bottom

edge

of

the

head

core).

2)

4-track

Erase

Head

At

playback

mode,

loosen

head

height

control

screws

(b)

(b’)

shown

in

Fig.

16,

and

adjust

so

that

the

upper

edge

of

the

tape

is

about

0.1

mm

lower

than

the

upper

edge

of

the

left

channel

head

core

of

the

4-track

erase

head.

14

3)

Recording

Head

At

playback

mode,

adjust

recording

head

height

by

turning

head

height

control

screws

(c),

(d),

(e)

shown

in

Fig.

16

to

left

and

right

until

the

upper

edge

of

the

tape

is

the

same

height

as

the

upper

edge

of

track-1

head

core

of

the

recording

head.

At

this

time

confirm

that

the

lower

edge

of

the

tape

is

also

the

same

height

as

the

lower

edge

of

track-4

head

core

of

the

recording

head.

4)

Playback

Head

With

head

height

control

screws

(f)

(g)

(h)

shown

in

Fig.

16,

adjust

the

playback

head

height

in

the

same

way

as

outlined

above

for

recording

head.

5)

After

the

various

head

height

adjustments

have

been

made,

confirm

that

the

core

side

of

the

heads

are

at

right

angles

with

the

chassis

during

tape

travel.

Sy

\\

SAME

WIOTH

(ABOUT

0.4mm)

FULL

TRACK

£.H.

4TRACK

E.H.

4.

HEAD

AZIMUTH

ALIGNMENT

1)

Playback

Head

a.

b,

Connect

a

high

sensitivity

V.T.V.M.

to

the

line

output

terminals.

Depress

the

“7-1/2

ips”

Tape

Speed

Selector

Switch,

set

Monitor

Switch

to

TAPE,

and

set

Stereo

Selector

to

“2

CH”

position.

Playback

an

Alignment

Test

Tape

(8,000

Hz

ampex

alignment

test

tape

recorded

at

3-3/4

ips).

.

At

playback

mode,

adjust

alignment

adjust-

ment

screw

(h)

shown

in

Fig.

16

by

turning

to

left

and

right

until

the

line

output

level

of

both

channels

is

maximum.

.

After

the

adjustments

outlined

in

(d)

above,

loosen

screws

(i),

(i)

and

move

the

head

gap

side

of

the

playback

head

to

left

and

right

until

there

is

no

fluctuation

in

output

level

(both

channels)

when

tension

is

applied

to

the

supply

reel.

Then

tighten

screws

(i)

(i’)

to

maintain

this

position.

|

Nl

Tr

amin

===)

ee

PB.

H.

Fig.

16

2)

Recording

Head

a.

Connect

an

Audio

Frequency

Oscillator

to

the

line

input

terminals

and

a

high

sensitivity

-

V.T.V.M.

to

the

line

output

terminals

and

load

a

blank

tape.

.

Set

the

Monitor

Switch

to

TAPE

position

and

record

a

16,000

Hz

signal

at

—10

dB.

.

When

the

above

adjustment

has

been

com-

pleted,

adjust

the

gap

side

of

the

recording

head

by

bending

recording

head

installation

angle

(i)

shown

in

Fig.

16

to

left.and

right

until

the

line

output

level

(both

channels)

does

not

fluctuate

when

tension

is

applied

to

the

supply

reel.

5.

For

optimum

adjustment,

repeat

Items

1

and

2

above

2

or

3

times.

Blank

testing

tape

should

be

new

tape.

15

pe

ee

a

ce

VI.

AMPLIFIER

ADJUSTMENTS

PB.

AMP.

PC.

BOARD

(1)

PB.

AMP

PC.

BOARD(2)

.

_

7

CH-|

FRONT

LEFT

CH-2

REAR

LEFT

CH-3

FRONT

RIGHT

CH:

4

REAR

RIGHT

oy

PB.

AMP

PC.

BOARD

(1)

AND

(2)

ARE

SAME

RC.

BOARD

MS~5022

Fig.

17°

VU

METER

SENSITIVITY

ADJ.

FRONT

REC.LEVEL

ADJ.

6X-280-SS

VR2

VR2b

VRI

.-

VRIb

HIGH

LINE

SENSITIVITY

OUTPUTS

_

V.T.

VAM,

Hig.

19

1.

PLAYBACK

OUTPUT

LEVEL

ADJUSTMENT

“

1)

Connect

a

high

sensitivity

V.T.V.M.

to

the

line

output

terminals.

~

2)

Depress

“7-1/2

ips”

Tape

Speed

Selector

Switch,

vRI

VRIb

vRI

VRib

-set

Monitor

Switch

to

TAPE,

and

set

Stereo

SSS

|

PB.

LEVEL

ADJ.

REAR

REC,

LEVEL

ADu.

Selector

to

“4

CH”

position.

3)

Playback

a

250

Hz

“0”

VU

recorded

test

tape.

Fig.

18

4)

Adjust

P.B.

Amp.

P.C.

Board

playback

level

adjustment

semi-fixed

resistors

VR1

(50

kB)

and

(A):

FRONT

P.B.

AMP.

P.C.

BOARD

MS-5022

VR1b

(50

kB)

shown

in

Fig.

18

(VR1

front/rear

(B):

REAR

P.B.

AMP.

P.C.

BOARD

MS-5022

left

channel;

VR1b

front/rear

right

channel)

to

(C):

FRONT

REC.

AMP.

P.C,

BOARD

MS-5023

obtain

a

V.T.V.M.

indication

of

4

dB

(1.228V)

(D):

REAR

P.B.

AMP.

P.C.

BOARD

MS-5023

on

each

channel.

E):

OSC.

P.C.

BOARD

KF-5010

©)

2.

VU

METER

SENSITIVITY

ADJUSTMENT

After

every

channel

adjustment

has

been

completed,

adjust

P.B.

Amp.

P.C.

Board

VU

meter

sensitivity

1

adjustment

semi-fixed

resistors

VR2

(5

kB).

and

VR2b

(5

kB)

shown

in

Fig.

18

(VR2

front/rear

left

channel;

VR2b

front/rear

right

channel)

to

ob-

tain

a

VU

meter

indication

of

“0”

VU

(0

position).

16

LEFT

CH.

VU.METER

SENSITIVITY

ADJ,

VR2 5KB

LEFT

CH,

PB,

LEVEL

ADJ.

VRI

50KB

RIGHT

CH, VU.

METER

SENSITIVITY

ADu,

VR2b

5KB

RIGHT

CH,

P.B.

LELEL

ADJ,

VRIb

5OKB

Fig.

20

P.B.

AMP.

P.C.

BOARD

(FACE

SIDE)

P.B.

AMP.

P.C.

BOARD

MS-5022

(REVERSE

SIDE)

17

ses

tcp

nance

igen

a5

le

mech

eh

cet

nei

a

al

ce

ea

eh

cn

eh

Socata

apr

oop

tah

apache

algerie

18

GX-280-SS

AUDIO

HIGH

FREQUENCY

LINE

|

SENSITIVITY

OSCILLATOR

.

INPUTS

V.T.V.M.

LEFT

CH,

REC,

LEVEL

RIGHT

CH.

REC.

LEVEL

ADJ.

VRI

5KB

ADJ.

VRib

SKB

Fig.

23.

REC.

AMP.

P.C.

BOARD

(FACE

SIDE)

TRIA,

1B,

2A,28,

3A,

3B,

----

25C458

LG

TR4A,4B,

---

2SC7II

TRSA,

5B,

---25C968

(@)(3)

Fig.

24

REC.

AMP.

P.C.

BOARD

MS-5023

(REVERSE

SIDE)

Fig.

22

REC,

HEAD

FREQUENCY

COUNTER

3.

RECORDING

LEVEL

ADJUSTMENT

1)

Connect

an

Audio

Frequency

Oscillator

to

the

line

input

terminals

through

an

attenuator

and

connect

a

high

sensitivity

V.T.V.M.

to

the

line

output

terminals.

2)

Depress

the

‘7-1/2

ips”

Tape

Speed

Selector

Switch

and

set

the

Stereo

Selector

to

“4-CH”

position.

7

3)

Set

line

recording

level

controls

to

maximum

and

load

a

Scotch

#111

blank

tape.

4)

Set

the

Monitor

Switch

to

TAPE

position

and

set

the

tape

deck

to

recording

mode.

Supply

a

1,000

Hz

signal

from

the

Audio

Frequency

Oscil-

lator,

and

adjust

the

attenuator

to

obtain

a

V.T.V.M.

indication

of

4

dB

(1.228V).

5)

Set

the

Monitor

Switch

to

SOURCE

position,

and

adjust

REC.

Amp.

P.C.

Board

recording

level

adjustment

semi-fixed

resistor

VR1

(5.

kB)

and

VR1b

(5

kB)

shown

in

Fig.

18

(VR1

front/rear

left

channel;

VR1b

front/rear

‘right

channel)

to

obtain

a

line

output

level

of

4

dB

on

each

channel.

.

RECORDING

BIAS

FREQUENCY

MEAS-

URING

METHOD

AND

ADJUSTMENT

MEASURING

METHOD:

Method

I

1)

As

shown

in

Fig.

25,

‘install

a

1

to

2

resistor

in

series

with

the

recording

head

and

connect

both

of

these

terminals

(a)

and

(b)

to

the

vertical

input

of

the

oscilloscope

and

set

deck

to

record-

ing

mode.

2)

Supply

a

sine

wave

to

the

horizontal

input

of

the

oscilloscope

from

the

Audio

Frequency

Oscil-

lator.

3)

Vary

the

oscillation

frequency

of

the

audio

fre-

quency

oscillator

until

the

oscilloscope

waveform

displays

a

circular

or

linear

pattern.

4)

If

the

oscillation

frequency

indication

is

within

100

to

110

kHz

when

a

circular

or

linear

pattern

is

displayed,

the

recording

bias

frequency

is

cor-

rect.

FROM

OSC,

AUDIO

FREQUENCY

o

OSCILLATOR

Fig.

25

Method

2

1)

Connect

a

Frequency

Counter

to

both

terminals

(a)

and

(b)

as

shown

in

Fig,

25.

Set

deck

to

recording

mode

and

take

a

frequency

counter

reading.

2)

If

the

frequency

counter

indication

at

this

time

is

within

100

to

110

kHz,

the

recording

bias

frequency

is

correct.

ADJUSTMENT

The

recording

bias.

frequency

can

be

adjusted

by

changing

the

value

of

OSC.

P.C.

Board

condenser

C4

(4500P/500

WV)

shown

in

Fig,

26.

.

RECORDING

BIAS

VOLTAGE

ADJUST-

MENT

(Frequency

Response

Adjustment)

1)

Connect

the

various

Measuring

instruments

in

the

same

way

as

outlined

in

“Recording

Level

Adjustment”

procedure,

2)

Follow

Recording

Level

Adjustment

procedure

through

Item

4

and

set

the

attenuator

to

—20

dB.

3)

Under

these

conditions,

adjust

OSC.

P.C.

Board

recording

bias

voltage

adjustment

trimmer

con-

densers

TC1

(front

left),

TC2

(front

right),

TC3

(rear

right),

and

TC4

(rear

left)

70P

shown

in

Fig.

26

to

obtain

an

equally

flat

frequency

response

at

1,000

Hz.

and

10,000

Hz.

4)

After

frequency

response

adjustment

is

complet-

ed,

the

recording

bias

voltage

is

within

2

to

5V

ALC,

5)

Proper

erase

voltage

is

within

65

to

70V

A.C.

NOTE:

Frequency

response

will

vary

depending

upon

the

tape

being

used.

(As

a

general

tule,

AKAI

100F

(Fuji

F)

tape

is

used.

19

Akai GX-2800D-SS User manual

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