Akai GX4000D Troubleshooting guide

SERVICE
MANUAL
PARTS
LIST
nooo. ADO
BESS
ALSO
APPLICABLE
TO
BLACK
PANEL
MODEL

AKAI STEREO TAPE DECK
voor. GX-4000D/DB
ALSO APPLICABLE TO BLACK PANEL MODEL
SECTION
1
SERVICE
MANUAL
........-.-----0
252
e
eee
3
SECTION
2
PARTS
LIST
.........----
2-002
s
ceteris
33
SECTION
3
SCHEMATIC
DIAGRAM
......--.----+--+--5-
59

II.
II.
VIE.
VUE.
SECTION 1
SERVICE MANUAL
TABLE OF CONTENTS
TECHNICAL: DATA 33:57. 220 bel cao aaa ee ae Fea 4
Is, “MODEL ‘GX-4Q00D 5. i2s.0 Bon ee fp avetain ates we yet 4
2. ‘MODEL -GX-4000DB -. ». 025600 4 ecg ets aan ee adiae gy Hoe 0s 5
DISMANTLING OF UNIT... 0... ee eens 6
CONTROLS: (feet fn susie aiden geal a inet tare wh 4 ae eae ks 8
PRINCIPAL PARTS LOCATION ........ 0.0.0.0. 0 cee eee eens 10
MECHANISM ADJUSTMENT .......... 0.000. c eee ee eee 11
1. PINCH ROLLER PRESSURE MEASUREMENT ..............-.. il
2. REEL TABLE BLOCK ADJUSTMENT .......... 00000000 eeu 1}
3. DRIVE BELT POSITION ADJUSTMENT ..............-.0005- 13
4. FLYWHEEL LOOSE PLAY ADJUSTMENT ............ 0.00000 13
5. AUTOMATIC SHUT-OFF OPERATING POINT ADJUSTMENT ...... 13
HEAD ADJUSTMENT ............0 0c c eee cece eee eens 14
1. HEAD HEIGHT ADJUSTMENT ....... 0.0.0.0 0. 000 cee eee 14
2. HEAD AZIMUTH ALIGNMENT ADJUSTMENT .............00. I4
3. HEAD ANGLE ALIGNMENT ADJUSTMENT ...........-..00-. 15
AMPLIFIER ADJUSTMENT ......... 00.00.00 ce cece eee eee es 16
Ts, MODEL GX4000D 12865 oss ig s song ah Ee peal Se eS 2s 16
2, “MODEL:.GX-4000DB:.. 022-3 fa ade ee ata alee ees 2 aes 18
DC RESISTANCE OF VARIOUS COILS ........... 00-0000 002 eee 20
CLASSIFICATION OF VARIOUS P.C BOARDS .........2...-.0-45 20
1. P.C BOARD TITLE AND IDENTIFICATION NUMBER ........... 20
2. MODEL GX-4000D COMPOSITION OF VARIOUS P.C BOARDS..... ak
3. MODEL GX-4000DB COMPOSITION OF VARIOUS P.C BOARDS .... 26
For basic adjustments. measuring methods. and operating principles, refer to GENERAL TECHNICAL
MANUAL.
ve

1. TECHNICAL DATA
1. MODEL GX-4000D
TRACK SYSTEM
4 track, 2 channel stereo/monaural system
REEL CAPACITY
Up to 7” reel
TAPE SPEED
wow & FLUTTER
7-1/2 and 3-3/4 ips
Less than 0.08% WRMS
FREQUENCY RESPONSE
DISTORTION (1,000 Hz “0” VU)
30 to 24,000 Hz +3 dB at 7-1/2 ips
30 to 16,000 Hz +3 dB at 3-3/4 ips
SIGNAL TO NOISE RATIO
Less than 1.0% at 7-1/2 ips
Better than 60 dB
(measured via tape with peak recording level)
ERASE RATIO
Better than 70 dB
BIAS FREQUENCY
100 kHz
HEADS
(3): One GX Recording head, one GX Playback head, one Erase head
MOTOR
(1): 4-pole induction motor
FF & REWIND TIME
200 sec using 1,200 ft. tape
OUTPUT JACKS
Line (2): 0.775V (“0" VU)
Required load impedance: more than 50 kohms
Phone (1): 100 mV/8 ohms
INPUT JACKS
Microphone (2): 0.25 mV
Required microphone impedance: 600 ohms
Line (2): 70 mV
DIN JACK
SEMICONDUCTORS
DIMENSIONS
WEIGHT
POWER REQUIREMENTS
Input: 2 mV/10 kohms, Output: 0.3V
Transistors: 24. Diodes: 13, FETs: 2, IC: 1
440(W) x 315(H) x 230(D) mm
(17.3 x 12.4 x 9.1")
13.2 kg (29.1 Ibs)
100V, 50/60 Hz for Japan
120V, 60 Hz for Canada & U.S.A.
220/240V, 50 Hz for European Countries & Australia
110/120/220/240V (Switchable), 50/60 Hz for the other Countries
a
2. MODEL GX-4000DB
TRACK SYSTEM
REEL CAPACITY
4 track, 2 channel stereo/monaural system
Up to 7” reet
TAPE SPEED
BI 7-1/2 and 3-3/4 ips
WOW & FLUTTER
Less than 0.08% WRMS
FREQUENCY RESPONSE
| 30 to 24,000 Hz +3 GB at 7-1/2 ips
30 to 16,000 Hz +3 dB at 3-3/4 ips
DISTORTION (1,000 Hz “0” VU)
Less than 1.0% at 7-1/2 ips
SIGNAL TO NOISE RATIO
Better than 60 dB
(measured
via
tape
with
peak
recording
level)
__|
Dolby
Switch
ON:
Improves
up
to
10
dB
above
5
kHz
ERASE RATIO
Better than 70 dB
BIAS FREQUENCY
r 100 kHz
HEADS
(3):
One
GX
Recording
head,
one
GX
Playback
head
one
Erase
head
MOTOR
+
(1):
4-pole
induction
motor
FF
&
REWIND
TIME
200
sec
using
1,200
ft
tape
OUTPUT JACKS Line (2): 580 mV “0” VU)
Required load impedance: more than 100 kohms
Phone (1): 100 mV/8 ohms
INPUT JACKS
DIN JACKS
SEMICONDUCTORS
DIMENSION
WEIGHT’
POWER REQUIREMENT
Microphone (2): 0.25 mV
Required microphone impedance: 600 ohms
Line (2): 70 mV
Input: 2 mV/10 kohms
Output: 0.3V
Transistors: 21, Diodes: 21, FETs: 2, ICs: 5
440(W) x 315(H) x 230(D) mm
(17.3 x 12.4 x 9.4")
13.2 kg (29.1 Ibs)
120V, 60 Hz for Canada & U.S.A.
220/240V,
50
Hz
for
European
Countries
&
Australia
e ‘: pels é f
For improvement purposes. specifications and design are subject to change without notice.
110/120/220/240V
(Switchable),
50/60
Hz
for
the
other
Countries
*
For
improvement
purposes.
specifications
and
design
are
subject
to
change
without
notice.
*
“Dolby”
and
the
Double
D
symbol
are
trademarks
of
Dolby
Laboratories.
(Manufactured
under
license
from
Dolby
Laboratories.)

ll. DISMANTLING OF UNIT
In case of trouble, etc. necessitating dismantling, please dismantle in the order shown in the photographs.
Reassemble in reverse order.
SiDE BCARD
SCREWS:
SCREWS
PiNCH ROLLER CAl
BACK BCAA
UPCER COVER
~d

Hl. CONTROLS
@eeeeeeeees
Seaeeoeseeoense
eevseeseosr
eeeccece
st Oh OUR NS
PINCH ROLLER
CAPSTAN
REEL RETAINER (Left)
SUPPLY REEL TABLE
HEAD COVER
TAPE GUIDE
INDEX COUNTER & RESET BUTTON
TRACK SELECTOR
VU METERS (Left & Right)
OUTPUT VOLUME
. HEADPHONE JACK
RECORDING INDICATOR LAMP
. RECORDING SAFETY BUTTON
. AUTOMATIC STOP LEVER
REEL RETAINER (Right)
. TAKE-UP REEL TABLE
. RECORDING/PLAYBACK LEVER
18,
19.
20,
21.
22.
23.
24,
25.
26.
27.
28.
29.
30.
31.
32.
33.
34,
Fig. 1 Controls
FAST FORWARD/REWIND LEVER
PAUSE LEVER
START BUTTON
POWER
MONITOR SELECTOR SWITCH (Tape & Source)
$.0.S. (Sound-On-Sound) BUTTON
MICROPHONE JACKS (Left & Right)
MICROPHONE RECORDING LEVEL CONTROLS
LINE RECORDING LEVEL CONTROLS
TAPE SELECTOR SWITCH
EQUALIZER SWITCH
DIN JACK
LINE OUTPUT JACKS (Left & Right)
LINE INPUT JACKS (Left & Right)
DOLBY N.R. INDICATOR LAMP
$.0.S. SWITCH/LINE RECORDING LEVEL CONTROLS
DOLBY N.R. SWITCH

IV.
PRINCIPAL
PARTS
LOCATION
V. MECHANISM ADJUSTMENT
TENTION SWITCH
Sw902
PAUSE LEVER
3 " : 9 th START SUTTON
TRACK
SELECTOR
; :
7
ats
y
swi
:
or
ae
POWER SWITCH
Swi
MEADPHON
: :
ao
By
:
HEADPHONE
VACK
eS
Pe
:
a
H
a
me
&
é
Le,
a
oe
4
ma
MACK
Bree
Fig. 4 Pinch Roller Pressure Measurement
MONITOR Sw -1
OUTPUT VRO $08 $w4.2
—_—
MIS REC LEVEL VR? 1
INE REC LEVEL vee
£9 Sw4-3 Lo rape SELECTOR Swa-4
Fig. 2 Front View (GX-4000D)
1. PINCH ROLLER PRESSURE
MEASUREMENT (Refer to Fig. 4)
!
Set the
recorder
in
the
PLAY
Mode.
Pull
the
pinch
‘
roller
1~2
mm
away
from
the
capstan
with
the
spring
¢90!
3
gauge
as
shown
in
Fig.
4.
Slowly
release
and
take
the
spring
gauge
reading
when
the
pinch
roller
touches
the
capstan
and
begins
to
rotate.
The
specified
pinch
roller
pressure
is
1
150~1
200g.
(Tape
speed:
7-1/2
ips)
POWER TRINSFORMER
Te0r tee gee MoroR M901
2. REEL TABLE BLOCK ADJUSTMENT
(Refer to Figs. 5, 6)
* Necessary points when measuring the tension
Wind the tape onto a 5” empty reel until there is a
diameter of 60 mm of tape. (See Fig. 5). Make the
end of the tape into a loop and put onto the spring
gauge.
: * Lug
E gh cult ddieo ee oe RINE_QUTPUT. JACKS LINE INPUT JACKS
DIN JACK
Fig. 3 Rear View (GX-000D) |
i
A.
SUPPLY
REEL
TABLE
BLOCK
ADJUSTMENT
1) RWD Tension Adjustment
A spring gauge reading of 400~500g in the
RWD Mode.
To adjust, increase or decrease the number of
(1) washers.
2) PLAY Mode Back Tension Adjustment
A
spring
gauge
reading
of
100~120g
in
PLAY
Mode.
To
adjust,
increase
or
decrease
the
number
of
(2) washers.
3) FF Free Tension Adjustment
A
spring
gauge
reading
of
15~20g
in
the
FF
Mode.
To
adjust.
move
the
position
of
puiley
(3)
back-
wards and forwards.
B.
TAKE-UP
REEL
TABLE
BLOCK
ADJUSTMENT
1) FF Tension Adjustment
A
spring
gauge
reading
of
400~500g
in
the
FF
Mode.
To
adjust.
increase
or
decrease
the
number
of
(1) washers.
2) PLAY Tension Adjustment
A spring gauge reading of 150~180g in the
PLAY Mode.
To
adjust,
increase
or
decrease
the
number
of
(2) washers.
3) RWD Free Tension Adjustment
A
spring
gauge
reading
of
15~20g
in
the
RWD
Mode.
To adjust. move the position of pulley (3) back-
wards and forwards.

SUPPLY REEL
TAGE
%
eLcock
TAKE-UP REEL
TAGLE O8LOCK
Fig. 6
LUTLIL EAU ATLLILLLUT DIMEN LAT OLY LECT ULLLL L RULLILEAS
AOJUSTMENT WASHER
Fig. 7
3. DRIVE BELT POSITION ADJUSTMENT
(Refer to Fig. 7)
Adjust position of drive belt so that it comes to the
center of the motor pulley by inserting a washer
(or washers) between the motor prop and mechanism
chassis as shown in Fig. 12.
4. FLYWHEEL LOOSE PLAY ADJUSTMENT
(Refer to Fig. 8)
With a minus screw driver, turn bearing to left and
right and adjust so that when the flywheel is moved
as indicated by the arrow mark in the figure, the gap
between the steel ball and flywheel supporting plate
is 0.3 mm as shown in Fig. 8. Fix at this position with
nut.
MICRO SWITCH
ADJUST WITH DRIVER
LELELLLSUS TSO LMLE ACAD LALIT S
MECHANISM CHASSIS
Fig. 8
A LEVER SHAFT———e{),
ot
5.
AUTOMATIC
SHUT-OFF
OPERATING
POINT
ADJUSTMENT
(Refer
to
Fig.
9)
Loosen
screws
(a)
and
(b)
and
adjust
installed
posi-
tion
of
Micro
Switch
so
that
when
AS
Lever
is
lowered
as
a
result
of
the
Power
Switch
being
set
to
SHUT-OFF
position,
the
gap
between
AS
Lever
is
about
5
mm.
i
se
eS
SS
Se

Vi. HEAD ADJUSTMENT
A EL
REC ANGLE PS ANGLE
tea) a) Ga 3. HEAD ANGLE ALIGNMENT
if | | ADJUSTMENT (Refer to Fig. 10)
1) Playback Head
a. Connect a High Sensitivity AC Voltmeter to the
left and right channel Output Terminals of the
tape deck.
b. Set the Track Selector to STEREO and set the
machine to 7-1/2 ips tape speed.
c. Playback an 8,000Hz 3-3/4 ips alignment
adjustment test tape.
d. Loosen screw (j). Adjust PB angle in the direc-
tion of the arrow and change the angle of the
head-to-tape contact.
Fix the PB head at a position where the output
level is not effected by an additional tension to
the supply reel.
TAPE
(e.g.
slightly
touching
the
supply
reel).
2) Recording Head
a. Connect an Audio Frequency Oscillator to the
z
line
input
through
an
Attenuator,
and
connect
es
200
"pe-20ir
4-240
(=
a
High
Sensitivity
AC
Voltmeter
to
the
line
output.
Then
load
a
blank
test tape.
Fig.
10
b.
Set
the
Monitor
Switch
to
SOURCE
and
supply
ig.
a 16,000Hz sine wave signal. Adjust the
Attenuator or the Line Recording Level Con-
trols to obtain a —20 dBm High Sensitivity AC
Voltmeter indication.
c. Reset Monitor Switch to TAPE and set deck to
recording mode.
1,
HEAD
HEIGHT
ADJUSTMENT
2.
HEAD
AZIMUTH
ALIGNMENT
d. Loosen screw (i). Adjust REC angle in the
(Refer
to
Fig.
10)
ADJUSTMENT
(Refer
to
Fig.
10)
direction
of
the
arrow
and
change
the
angle
of
1)
Erase
Head
1)
Playback
Head
the
head-to
tape
contact.
Loosen screws (a) and (b) shown in Fig. 10 and
adjust erase head height. Tighten screws at posi-
tion at which the upper edge of the tape is 0.1 mm
lower than the upper edge of the left channel head
core of the erase head.
2) Recording Head
Adjust head height adjustment screws (c) and (d)
shown in Fig. 10 so that the upper edge of the
tape and the upper edge of left channel head core
of the recording head are the same height.
3) Playback Head
Adjust head height adjustment screws (f) and (g)
shown in Fig. 10 so that the upper edge of the
tape and the upper edge of left channel head core
of the playback head are the same height.
a. Connect a High Sensitivity AC Voltmeter to
the left and right channel Output Terminals of
the tape deck.
b. Set the Track Selector to STEREO and set the
machine to 7-1/2 ips tape speed.
c. Playback an 8,000Hz 3-3/4 ips alignment
adjustment test tape.
d. Adjust adjustment screw (h) to obtain max-
imum High Sensitivity AC Voltmeter indication
on both channels.
2) Recording Head
a. Connect an Audio Frequency Oscillator to the
line input through an Attenuator, and connect
a High Sensitivity AC Voltmeter to the line
output. Then load a blank test tape.
b. Set the Monitor Switch to SOURCE and supply
a 16,000Hz sine wave signal. Adjust the
Attenuator or the Line Recording Leve! Con-
trols to obtain a —20 dBm High Sensitivity AC
Voltmeter indication.
c. Reset Monitor Switch to TAPE and set deck to
recording mode.
d. Adjust adjustment screw (e) to obtain max-
imum High Sensitivity AC Voltmeter indication
on both channels.
Fix the REC head at a position where the out-
put level is not effected an additional tension to
the supply reel.
(e.g. slightly touching the supply reel).
NOTES: 1. As head adjustment greatly affects
tape deck performance, be sure that
these adjustments are carried out
properly.
. Be careful not to use magnetized tools
near the heads.
. As the level of old tape varies greatly.
use new tape.
4. Demagnetize heads before and after
head adjustment.
i)
wW

Vil. AMPLIFIER ADJUSTMENT
HIGH SENSITIVITY
ene
AC
VOLTMETER
OSCILLATOR
OUT IN
FREQJENCY
COUNTER
Fig. 11 Instruments Connection
1. MODEL GX-4000D
‘ee
®)
VES 23mH
REC AMP BIAS FILT|
CtaRT SAS FER
YRE_5KB
\U METER SENS
(RIGHT)
VR4 5KB
REC LEVEL
1
2, 23 ni
AMP BIAS FILT
IGHT) 6 FireR
VL4 23m
REC AMP BIA!
igus PUTER RESPONSE
wag
7
a
ey
raton
me
{RIGHT} Be LeveL
VU to WL
Adjust from the oppose sae
(@)
Fig. 12. Amp P.C Board LE-5801A (GX-4000D)
Step
|
Adjustment
Test
Tape
\
Adjustment
Item
{Supply
Signal
Mode
Point
Result
Remarks
Playback
|
700
H
L
Level
|
7-1/2
-
VR2
50
kB(L)
haar
i
;
f
2
ied
+
Monitor
Switch
to
Adjustment
eae
a
vrs
50
BR)
proce
“TAPE
:
i
|
|
|
(0.778V)
APE”.
VU
Meter
700
Hz
i
|
2
Sensitivity
7-1/2
ips
pray
|
WR3
5
KB(L)
|
OVU
Adjustment
|
Test
Tape
VR6
5S
KB(R)
indication
|
SCOTCH
#2
re
Frequency
tape
1,000
.
(Bae
3
|
Response
ipod
Ha
|
RECE
|
MCL
ZORL)
Py
GGL.
4
|
SARC
SRE
ate
ee
aeer:
Adjustment
-20
VU
pre
See
sR
|
aa
ica
ine
recording
4
poets
ci
SCOTCH
#211
ood
tape
1,000Hz
|
REC/
|
REC
Volume
i
oe
Set
Monitor
Switch
to
’
ecording
|
0
VU
recording
PLAY
|
(VRB
SOKA)
|
775yy_
|
“TAPE”
eve.
:
Adjustment
SCOTCH
#211
[
REC/
|
VRI
Sk
O.dbm
tape
1,000
Hz
B(L)
2
Set
M
i
4
;
+0.5
dB
onitor
Switch
to
OVUrecording
|
PEAY]
VR4
SBR)
|g
azsyy_|
“SOURCE™
oe
an
ae
5
re
cant
5
Adjustment
Test
Tape
Adjustment
|
Step
lied
Supply
Signal
|
moi
Paint
Result
Remarks
os
ae
Distortion
1,000
Hz
5
Factor
0
VU
REC/
Less
than
(Refer
to
NOTE
5)
‘
2
A
PLAY
1.0%
j]
eA
recording
a
PB
Amp
Bias
100
kHz
Minimum
Set
Monitor
Switch
to
6
Filter
from
an
REC
as
=
aes
AC
Voltmeter
|
“TAPE”.
Adjustment
oscillator
7
m™
indication
(Refer
to
NOTES
6,
7)
T
.
:
REC
Amp
Bias
100
kHz
Minimum
Set
Monitor
Switch
to
7
Filter
from
an
REC
bot
5
aay
AC
Voltmeter
|
to
“SOURCE”.
Adjustment
oscillator
"
indication
(Refer
to
NOTES
6,
7)
|
=e
ack
os
a
Chart-1
NOTES:
1.
Output
Level
Control
should
be
at
maximum.
2
3
4
5
6
d,
.
Except
for
Step
3,
set
tape
speed
to
7-1/2
ips.
.
Set
tape
selector
to
Low
Noise
position.
.
(L)
=
Left
Channel,
(R)=
Right
Channel.
_
If
it
does
not
comply
with
the
specifications,
repeat
Steps
3,
4
and
re-adjust.
.
Unless
the
core
is
moved
intentionally
this
adjustment
is
not
necessary.
.
Adjust
the
oscillator’s
frequency
to
give
a
frequency
counter
reading
of
100
kHz.