Akai GXC-570DII User manual

SERVICE
MANUAL
PARTS LIST

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SECTION 1 SERVICE MANUAL ............----555- 3
SECTION 2 PARTS LIST ............000 ee eee ees 39
SECTION 3. SCHEMATIC DIAGRAM ............-..--- 64

Il.
Il.
IV.
Vil.
VII.
IX.
SECTION 1
SERVICE MANUAL
TABLE OF CONTENTS
TECHNIGAL- DATA (carcoeie MAAAd Go ee Va RNA dre ON weitere dale CaS dee Be BOS 4
DISMANTLING OF UNID ocd ose bs ga ore tet a haw et oad aoe nena 5
CONTROLS
4.56055
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PRINCIPAL
PARTS
LOCATION
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CIRCUIT OPERATING PRINCIPLES ......0.0.0 00 ccc eee cence ene eet eee tees 8
1. SYSTEM CONTROL OPERATION ......0. 0.000 cece cc eet eect ee ene ve 8
2 TOUCH. BUTTON OPERATION fx o503 ain cate iaita beater tate Se eee aed Ree a6 16
MECHANISM
ADIUSTMENT
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1.
FLYWHEEL
THRUST
LOOSE
PLAY
ADJUSTMENT
........
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2.
REEL
TABLE
INSTALLATION
POSITION
ADJUSTMENT
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3.
PLAY
PLUNGER
INSTALLATION
POSITION
ADJUSTMENT
...........0
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4.
PAUSE
PLUNGER
INSTALLATION
POSITION
ADJUSTMENT
..........
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19
5.
PINCH
ROLLER
PRESSURE
ADJUSTMENT
............00000505
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Bed
20
6.
TAKE-UP
TORQUE
AT
VARIOUS
MODES
AND
TORQUE
MEASURING
METHOD
.........
20
7
LID
PANEL
POSTTION
ADJUSTMENT
4%...
¢.i520iis
tees
Po
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ENG
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SS
20
HEAD
ADIUSIMENT.
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kates
21
1.
TAPE
GUIDE
HEIGHT
ADJUSTMENT
.......
Bes
dates,
Brad
Noa
Lea
sind
ale
tone
Mie
21
2,
HEIGHT
ADJUSTMENT
OF
RECORDING/PLAYBACK
COMBINATION
HEAD
.........---
me
3. AZIMUTH ALIGNMENT ADJUSTMENT OF RECORDING/PLAYBACK
COMBINATION
HEAD
.....
21
AMPLIFIER
ADIUSIMENT
6.45003.
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22
DC
RESISTANCE
OF
VARIOUS
COILS:
2.
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Sa
bea
inde
pede
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ed
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Sees
24
CLASSIFICATION
OF
VARIOUS
P.C
BOARDS
.........
000
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teens
25
1.
RELATION
OF
P.C
BOARD
TITLE
AND
IDENTIFICATION
NUMBER
.........
7
gianatespeishys
26
2.
COMPOSITION
OF
VARIOUS
P.C
BOARDS
..........
00
cece
ee
enna
26
For
basic
adjustments,
measuring
methods,
and
operating
principles,
refer
to
GENERAL
OPERATING
PRINCIPLES
AND
ADJUSTMENTS.

I. TECHNICAL DATA
a
ETE
Sal
TRACK SYSTEM 4 track, 2 channel Stereo System
TAPE ___| Philips Type Cassette
TAPE SPEED 1-7/8 ips (Pitch Control +6%)
WOW & FLUTTER Less than 0.06% WRMS, 0.17% (DIN 45500. 45507)
FREQUENCY RESPONSE
35 to 15,000 Hz +3 dB, using LN tape
35 to 16,000 Hz +3 dB, using LH tape
35 to 17,000 Hz +3 dB, using CrO, (SA) tape
35 to 19,000 Hz +3 dB, using FeCr tape
DISTORTION (1,000 Hz “0” VU)
Less than 1.0% using LN tape
Less than 1.0% using LH tape
Less than 1.5% using CrO, (SA) tape
Less than 1.5% using FeCr tape
SIGNAL TO NOISE RATIO
Better than 51 dB using LN tape
Better than 51 dB using LH tape
Better than 52 dB using CrO, (SA) tape
Better than 52 dB using FeCr tape
(measured via tape with peak recording level of +5 VU)
Dolby N.R. switch ON: Improves up to 10 dB above 5 kHz
ERASE RATIO Better than 70 dB
BIAS FREQUENCY | 100 kHz
HEADS
(3):
GX
recording
head,
GX
playback
head
and
erase
head
(3 head system)
MOTORS
(3):
One
DC
FG
Servo
motor
for
capstan
drive,
and
two
DC
motors
for
F.F. & REWIND TIME
reel drive
50 sec. using a C-60 cassette tape
OUTPUT JACKS Line (2): 410 mV (0 VU)
Required load impedance: more than 47 kohms
Phone (1): 300 mV/8 ohms (Variable at Max Volume)
INPUT JACKS Microphone (2): 0.25 mV (Input impedance 2.4 kohms)
Required microphone impedance: 600 ohms
Line (2): 70 mV (Input impedance 100 kohms)
SEMICONDUCTOR Transistors: 98, Diodes: 112, FETs: 4, ICs: 17
POWER REQUIREMENTS CSA,UL & LA model: 120V/60 Hz
Australia model: 240V/50 Hz
Japan model: 100V, 50/60 Hz
Other models: 110 to 120/220 to 240V, 50/60 Hz
DIMENSIONS 440 (W) x 255 (H) x 225 (D) mm
(17.3 x 10.0 x 8.9”)
WEIGHT 9.5 kg (21.0 lbs)
* For improvement purpose, 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.)

li. DISMANTLING OF UNIT
In case of trouble, etc. necessitating disassembly,
please disassemble in the order shown in photographs.
Reassemble in reverse order.
FRONT PANEL
SCREWS & CONTROL KNOBS
SCREWS & CONTROL KNOBS
SCREWS
CABINET
Y
%
b
SCREWS
SELECTOR BOX
& DUST COVER SCREWS
LID PANEL.

OO STOP OF Be OES
CONTROLS
[toon ae
GRASS A TAL TERRITE HEAD.
PITCH CONTROL
PHONE LEVEL CONTROL
TAPE SELECTOR
CAL TONE SWITCH
REC CALIBRATION CONTROLS (Left and Right)
DOLBY N.R. SWITCH AND INDICATOR LAMP
MPX FILTER SWITCH
LIMITER SWITCH
DOOR SWITCH
EJECT SWITCH
CASSETTE RECEPTACLE LID
INDEX COUNTER AND RESET BUTTON
REPEAT BUTTON
MEMORY REWIND BUTTON
LEFT MICROPHONE RECORDING LEVEL CONTROL
RIGHT MICROPHONE RECORDING LEVEL CONTROL
PAUSE BUTTON AND INDICATOR LAMP
RECORDING BUTTON AND INDICATOR LAMP
REWIND BUTTON AND INDICATOR LAMP
STOP BUTTON
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
Fig. 1 Controls
PLAY BUTTON AND INDICATOR LAMP
FAST FORWARD BUTTON AND INDICATOR LAMP
LEFT VU METER/PEAK METER
PEAK METER INDICATOR
VU METER INDICATOR
RIGHT VU METER/PEAK METER
METER SELECTOR
LEFT LINE RECORDING LEVEL CONTROL
RIGHT LINE RECORDING LEVEL CONTROL
TAPE MONITOR SWITCH
POWER SWITCH
HEADPHONE JACK
MICROPHONE JACKS (Left and Right)
OUTPUT LEVEL CONTROL
LINE OUTPUT JACKS (Left and Right)
LINE INPUT JACKS (Left and Right)
REMOTE CONTROL JACK
‘AC INLET
VOLTAGE SELECTOR SWITCH

IV. PRINCIPAL PARTS LOCATION
CAL TONE SWITCH SWI DOLBY N.R. INDICATOR Di
TAPE SELECTOR SWITCH DOLBY AR. SWITCH SW2-3
sw3
PHONE
LEVEL
VOLUME
REC
CALIBLATION
MPX
FILTER
SWITCH
SW2-2
VRI VOLUME VR2
PITCH
CONTROL
VR4
=
3
LIMITER
SWITCH
SW2-|
L R
VU/PEAK METER
DOOR
BUTTON
——=
MgO!,
902
PEAK
EJECT
BUTTON
METER
SELECTOR
yy
{INDICATOR
METER SELECTOR
SWITCH SWI
INDEX COUNTER
LINE REC VOLUME
VR2
HEAD BLOCK
MIC REC VOLUME VRI
Te POWER SWITCH SWI
[eel
TOUCH
BUTTON
SWITCH
kL
R
HEADPHONE
JACK
J9OIC
a
REPEAT SWITCH SWI MIC JACK
J90la,b
MONITOR SWITCH SWI
MEMORY SWITCH SW2 OUTPUT VOLUME VRi
Fig. 2 Front View
REEL MOTOR (RIGHT)
PEAK CIRCUIT P.C BOARD CAPSTAN MOTOR NOISE FILTER PC BOARD Cl-2027
C\-5203
AMP P.C BOARD C!~5202A MOTOR F.G. } REEL MOTOR (LEFT)
fugHt AePT
TNE ODT
PLAY PLUNGER
SL9OI
FLYWHEEL (LEFT)
FLYWHEEL (RIGHT)
i
REMOTE CONTROL
AC INLET POWER TRANS PAUSE PLUNGER
J902 sLgo0e2 JACK
VOLTAGE SELECTOR POWER SUPPLY PC BOARD SYS,CON PC BOARD
Sw906 C1I-5206 C1- 52098
Fig. 3 Rear View

V.
CIRCUIT
OPERATING
PRINCIPLES
1. SYSTEM CONTROL OPERATION
NOT
CIRCUIT
TRUTH TABLE
NAND
CIRCUIT
NOR
CIRCUIT
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13

1-1. TAPE SLACK ELIMINATION CIRCUIT
1) The purpose of this circuit is to take up tape slack
prior to operation for proper tape tension at all times.
The double capstan system of this deck is vulnerable
to tape tangling around the capstan when. the PLAY
mode is effected with a noticeable tape slack and to
poor head-to-tape contact for a considerable length
of time in the beginning of tape even with a slight
tape slack.
At the same time, TR37 base electric potential is
decreased through D42 and PR66 to turn on TR35
and TR37. For this reason, Supply and Take-up Reel
Motors are supplied with electric currents to start
_ totation through R35, TR35 and R37, TR37,
respectively. But because the rotations are in the
opposite direction, the torques are toward pulling
the tape on both sides which causes the tape to
stand still. In this way, weak torques prevent tape
2) When the cassette tape is not loaded, the cassette slack from forming and function as a parking break.
tape detection micro switch SW902 is CLOSED and
the
deck
maintains
TR28
OFF>TR40
ON>TR34
1-2.
PLAY
PLUNGER
OPERATION
CIRCUIT
1) This circuit operates the Play Plunger by first sup-
OFF condition. Even when the EJECT is operated
to OPEN SW902, the EJECT switch SW903 is
CLOSED beforehand to maintain the above TR28,
TR40, TR34 condition.
However, when the cassette tape is loaded, as EJECT
switch SW903 becomes OPEN and as SW902 is
OPEN, the charging current flows in the order of
D25>D26>PR88~>C31 to charge C31.
While C31 is being charged, TR28 is OFF to result
in High Level IC3D input terminals 9 and 10 and Low
Level output terminal 8. This decreases the base
electric potential of TR40 and TR40 turns OFF.
Because TR40 collector is connected to TR34
through PR77, when TR40 turns OFF, TR34 base
electric potential increases and turns ON. Thus,
because electric current flows to Supply Reel Motor
through R34, the Supply Reel Motor rotates to take
up the tape slack.
3) Meanwhile, TR28 turns ON when C31 is charged by
the electric current flowing from D25>D26-PR88
C31.
The duration of this charge is approximately 2 to 3
seconds. Or, TR28 can be turned ON in another way,
when the Supply Reel Motor rotates to pull the tape,
Take-up Reel Motor starts to rotate after the tape
slack is completely taken up. When the Take-up
Reel Motor starts to rotate, the rotary magnet within
SW901 interlocked with the tape counter starts to
rotate. This results in a pulse electric current to flow
through the Automatic Stop Circuit C1-TR1>C2
>D2 and System Control Circuit PR7~C31 to charge
C31 and to turn ON TR28. In either way, when
TR28 is turned ON, IC3D Low Level input terminal
9 and High Level output terminal increase TR40 base
electric potential through PR83-C42-PR84 and
TR40 is turned ON.
When TR40 is turned ON, the base electric potential
of TR34, which is connected to TR40 collector
through PR77, decreases and TR34 is turned OFF.
The electric current is thereby cut from the Supply
Reel Motor and Supply Reel Motor stops.
4) Also, turning ON of TR28 results in a Low Level
input terminal 13 of IC9D and High Level output
terminal 12. This causes TR35 base electric potential
to increase through PR62 and PR59 from 5V line and
turns TR35 ON. When TR35 turns ON, the electric
potential of D39 cathode side decreases, and base
electric potential of TR35 is thereby decreased
through D38 and PR65.
plying a big amount of electric current to start
operation, then a small amount to maintain operation.
This deck employs transistors rather then relays for
the drive.
2) Because the PLAY mode of the deck results in a Low
Level IC9B output terminal 4 of the System Control
Circuit, base electric potential of the Power Supply
Circuit TR12 connected to the output terminal 4
decreases and TR12 is turned OFF. When this
happens, charging current flows from TR4 emitter to
C16 through R19. Then while C16 is being charged,
TRI10 base electric potential increases to turn TR10
ON, and collector current flows to operate the Play
Plunger. Also, when TR12 is turned OFF, TRS base
electric potential increases and TRS is turned ON.
As a result, Play Plunger maintains operation even
after C16 is finished being charged and TR1O is
turned OFF, because TRS collector current flows
in through D9 and R7.
3) At the instance the Power Switch is turned on in the
Power Supply Circuit, TR12 is OFF from the time
SV electric voltage is introduced into the TR3 emitter
to the time System Control Circuit begins operation.
This causes charging current to flow to C16, to turn
ON TRIO, and the collector current to flow to the
Play Plunger to result in a malfunction. For this
reason, from the time electric voltage is introduced
into the TR3 emitter to the time System Control
Circuit begins operation, a charging current flows
from the TR4 emitter through R16-C17-R17 to
increase base electric potential of TR11 and turn it
ON. When TR11 is turned ON, the D16 anode side
reaches ground potential so that TR10 is at OFF
condition and the plunger does not operate. Because
the time it takes to charge C17 and turn on TR11 is
longer than the time it takes for the System Control
Circuit to operate and turn on TR12, such malfunc-
tion is prevented.
1-3 FAST FORWARD AND REWIND SPEED
CONTROL CIRCUIT
1) The reel motors employed in this deck are DC motors
which at a nonload condition rotates at a very high
speed. Consequently, when Fast Forward or Rewind
is effected, there is a possibility of tape damage due
to a gradual buildup of inertia and increased
revolutions. This circuit is for the purpose of con-
trolling supply voltage to the take-up reel motor for
14

suppression of increased motor revolutions.
2) When the deck is set to Fast Forward mode, TR38
is turned ON and the take-up motor begins to rotate.
In case the supply reel motor does not rotate, bias is
not supplied to the base of the Power Supply P.C
Board TR9 and the resistance between TR9 collector
and emitter is infinite.
Therefore, a fixed bias is supplied to TR8 through
R11, D13 and C15 and a fixed DC voltage is supplied
to the take-up reel, to result in gradual build-up of
inertia and increase in motor revolutions. However,
at Fast Forward mode, the supply reel motor of this
deck functions as a generator. Accordingly, the
electromotive force generated by the supply reel
motor passes D44 and Power Supply P.C Board R15
to become TR9 base bias, and the resistance between
TR9 collector and emitter varies proportionately with
the extent of the generator’s electromotive force.
In other words, the resistance between TR9 collector
and emitter is interconnected to TR8 base-emitter
interval in parallel and varies the bias supplied to
TR4.
For instance, when the take-up reel motor begins to
rotate at high speed, proportionate electromotive
force is generated by the supply reel motor and this
generated voltage increases the resistance between
TR8 collector and emitter thereby decreasing the
supply voltage to the take-up reel motor. Thus the
motor revolution is slowed down. In this manner,
the take-up speed always corresponds with the supply
reel motor speed, thus preventing high speed motor
revolutions.
3) Speed control also functions in exactly the same way
at Rewind mode. However, in this case, the right
hand side reel motor functions as a generator and
controls the supply voltage in order to control the
left hand side reel motor revolutions. Thus the
Rewind speed is controlled in the same way as at
Fast Forward.
1-4 AUTOMATIC SHUT-OFF MECHANISM
CIRCUIT
1) This circuit automatically effects Stop mode from
other modes, i.e., Play, Recording, Fast Forward or
Rewind modes, when tape travel stops.
2) The rotation of the rotary magnet within SW901
during tape travel generates pulse and TRI of the
Automatic Shut-Off Circuit repeats ON-OFF
switching operation. By the switching operation of
TR2, charge and discharge current flows to C2.
Only when C2 is charged, C3 is charged through D3
and TR2 base electric potential increases to turn
TR2 ON. When C2 is discharged, C3: discharging
current flows to R6>R7~Ground and TR2 base
electric potential is gradually decreased. But because
C3 is charged by C2 charging current before TR2
turns OFF, the ON condition of TR2 is maintained.
For this reason, TR3 base is ground electric potential
and therefore, TR3 is OFF.
3) When tape travel stops, charging and discharging of
C2 stops, discharging of C3 is completed, and TR2
is turned OFF. Consequently, TR3 base electric
potential increases to turn ON and TR23 (Sys. Con
P.C Board) collector connected to TR3 collector also
reaches ground electric potential. As a result Stop
mode is effected.
15

2.
TOUCH
BUTTON
OPERATION
EQUIVALENT
CIRCUIT
OUTPUT
E R7
O+5V
+B (22V) , ne
O
sree
a
O OUTPUT
Ci
MAL-FANCTION ON ~~
PREVENTION CAPACITOR
PALSE GENERATOR RECTIFCATION
CIRCUIT CIRCUIT
Fig. 4
CHARGE CURRENT
COMMERCIAL.
CURRENT
\
" HUMAN BODY
(SIGNAL SOURCE)
DISCHARGE CURRENT
Fig. 5
HUMAN BODY
(CAPACITOR)
DISCHARGE CURRENT
Fig. 6
16

TRI BASE
TRI,2
3V p-P
COLLECTOR
eet
ee
eae,
0.8V
TR3
BASE
TR3
COLLECTOR
t
WHEN TOUCH BUTTON IS TOUCHED
2-1 CIRCUIT COMPONENT
As shown in Fig. 4, Touch Button System Circuit
can be generally divided into a pulse generator
circuit and rectifier circuit, and includes malfunc-
tion prevention capacitor, transistor protection
resistor and diodes, etc.
As shown by the equivalent circuit in the diagram,
last stage transistor TR3 performs the exact same
function as a micro switch.
2-2 WHEN THE FINGER TOUCHES THE
BUTTON ONLY (Refer to Figs. 5 and 7)
There is an inductance in our bodies from com-
mercial power supply (50 Hz or 60 Hz) and as
shown in Fig. 5, our bodies are equivalent to a kind
of a signal source.
Accordingly, if there is a kind of a signal source, to
touch a touch button is same as supplying a signal
to it.
As shown in Fig. 5, when a button is touched with
a finger, a signal is supplied to TRI base.
When a signal is not supplied to TR1, base bias is
supplied by R5 and R4. But because the electric
potential is low, it does not function in full capacity.
Also, TR2 is supplied with base bias from TR1 but
is not in full operation. C3 is charged to an extent
equivalent to TR2 collector voltage.
The signal supplied to TR1 base turns ON @ side of
TR1 completely and turns OFF the ey side that
Fig. 7
TR2
repeats
ON
and
OFF
also.
When
TR2
is
turned
ON,
C3
is
discharged
through
TR2
and
D2;
and
when
TR2
is
turned
OFF,
C3
is
charged
and
this
pulse
is
rectified
at
D1
and
charged
at
C4
to
increase
TR3
base
electric
potential.
TR3
is
thereby
turned
ON.
2-3
WHEN
THE
FINGER
TOUCHES
THE
BUTTON
WHILE
ANOTHER
FINGER
OR
HAND
IS
TOUCHING
THE
DECK
CHAS-
SIS
(Refer
to
Fig.
6)
The
above
explains
how
a
touch
button
operates
with
the
human
body
as
a
signal
source.
It
takes
advantage
of
the
fact
that
a
human
body
can
be
used
as
a
capacitor.
As
shown
in
Fig.
6,
when
the
button
and
chassis
are
both
touched
by
the
finger(s),
it
is
the
same
as
if
a
capacitor
has
been
placed
as
shown
in
the
circuit
diagram.
Electric
charge
of
C2
discharges
to
RI@Co>R4.
As
can
be
seen
by
the
circuit,
this
discharging
period
is
very
short.
During
this
short
period
of
discharge,
TR1
is
turned
OFF,
TR2
collector
electric
potential
increases,
and
C3
is
charged.
C4
is
charged
by
the
charging
current
of
C3,
and
TR3
base
electric
potential
increases.
TR3
is
there-
by
turned
ON
and
functions
in
the
same
way
as
a
micro
switch.
a
SSS
SS
SS
17

Vi. MECHANISM ADJUSTMENT
CAPSTAN
CAPSTAN MOTOR
FLYWHEEL B
(RIGHT )
DRIVE BELT
EWN EEL
FLYWHEEL A
as ae (LEFT)
ee
eee
ees
mess
=
Lag a
‘¥ 0.05 to 0.15 mm
MOTOR PULLEY
FIXATION NUT ADJUSTMENT SCREWS
Fig. 8 Flywheel Thrust Loose Play Adjustment
1. FLYWHEEL THRUST LOOSE PLAY AD-
JUSTMENT (Refer to Fig. 8)
Adjust by turning flywheel thrust loose play adjust-
ment screws to obtain a 0.05 to 0.15mm of loose
play when the flywheel is moved as indicated by the
arrow mark.
Tighten fixation nuts to maintain optimum adjusted
condition. Paint lock the adjustment screws.
2. REEL TABLE INSTALLATION POSITION
ADJUSTMENT (Refer to Fig. 9)
Adjust until a clearance of approximately 3.2mm is
obtained between the mecha frame and the lower
side of the reel table’s pulley as shown in Fig. 9.
Then, tighten the fixation screw firmly.
MECHA FRAME
FIXATION SCREW
REEL MOTOR
Fig. 9

ADJUSTMENT
SCREWS
.PLAY PLUNGER INSTALLATION POSI-
TION ADJUSTMENT (Refer to Fig. 10)
The clearance between the head base and head clutch
plate when the plunger is moved as indicated in Fig.
10 at stop mode should be approximately 1.0mm.
If not, adjust play plunger position with the adjust-
ment screws in the direction as indicated by the
PINCH ROLLER
PINCH ROLLER
Fig. 10
arrow mark.
N H;
1 Mt yous
OO) che OO)
CASSETTE TAPE
PLAY POSITION
PAUSE POSITION
.PAUSE PLUNGER INSTALLATION POSI-
TION ADJUSTMENT (Refer to Fig. 11)
With the tape loaded, the Pause Plunger Solenoid is
not completely pulled if the head base does not lower
at all when the mode is changed from PLAY -to
PAUSE. In order to allow Pause Plunger to function
completely and still have the head not lowered too
HEAD BASE
mre st
a
{be PAUSE
| PLUNGE
!
S a)
ADJUSTMENT SCREW
Fig. 11
much, the head base should lower only 0.1mm
(lower only slightly) when the mode is changed from
PLAY to PAUSE as shown in Fig. 11.
If you find that the plunger function is not com-
plete, adjust by lowering the Pause Plunger Instal-
lation Position approximately O.lmm using the
adjustment screw.
et
19