Hitachi MX-W50 - Performance Checks; CIRCUIT DIAGRAMS; Main P.W.B. & CD Section Diagrams

CD PLAYER SECTION
When carrying out adjustment of the PX P.W.B., remove the
Key P.W.B. and, after connecting an adjutment jig to the
test point (refer to DISASSEMBLY Fig. 7), place a disc in the
unit and then adjust.
Adjustment procedure
Whenever any of the operations listed below are carried out,
then, without fail, make sure to perform the circuit adjust-
ments described in section 1 — 3 below.
(1) Replacement of parts and Overhaul in the Unit Mechan-
ism Assembly
(2) Replacement of parts in the Pickup Unit
(3) Replacement of parts in the CD power supply circuit
CD PLAYER CIRCUIT ADJUSTMENT
Note) If the adjustment is being made following the
replacement of parts in the Pickup Unit, preset the
Variable Resistors as shown in the table below.
@ Presetting
: Preset
Adjustment os
Position
Laser Diode Output VR901
Tracking Servo Offset VR902
Adjustments should be made in the following sequence:
574 z
GFS e—e
On es) ea
o—* WFCK
PX P.W.B.
OCs
0
TP.5(TC1)@ @TP. 4 (GND) VR901
©)
VR902
LASER DIODE
OUTPUT ADJ.
TRACKING SERVO
OFFSET ADJ.
TP. 3(TER)@ ;
TP. 2 (EFM)@
® TP. 1 (GND)
-7-—
MX-W50
Cautions on CD Operation
The MX-W50 turns OFF all power to the CD unit other than
that to the function CD (IC 907, however, remains ON).
You must therefore carry out the following when adjusting
the PX P.W.B. Assy independently.
Set the POWER ON/OFF switch to ON.
The CD POWER ON command is output from Pin © of IC 907
when the power is turned ON.
1. Laser Diode Output Adjustment
Note) Do not perform this adjustment except when the
Pickup Mechanism, Laser Circuit or the CD Power
Circuit has undergone replacement of parts.
(1) Instrument to be used
Oscilloscope
(2) Adjusting Procedure
1) Connect the oscilloscope to TP. 2 (EFM) and TP. 1 (GND)
(Fig. 33).
2) Load a disc into the player, clamper in, set the Laser,
Open/Close Switch to “ON” and take a reading of the
EFM signal with the oscilloscope.
Note) When the Laser,Open/Close switch is “ON” never
peek into the lens. This is very dangerous.
How to Read the EFM Signal Wave Form and Procedure for
Connecting the Oscilloscope
Oscilloscope
TP.2
(EFM)
TP.1
(GND) O
Fig. 33
3) Adjust the VR901 so that the amplitude of the EFM signal
in the oscilloscope reaches a level of 1.3 V + 40 mV.
Note)
However,
if
the
signal
level
is
within
the
range
of
1.1
—
1.5V,
it
is
normal
and
no
adjustment
is
neces-
sary.
+1.3V
ov
Fig. 34
MX-W50
2. Tracking Servo Offset Adjustment
(1) Instrument to be used
DC Voltmeter
(2) Adjustment Procedure
1) Steps 1 is post adjustment procedures.
2) While in the “Stop” mode, connect the DC voltmeter to
TP. 3 (TER) and TP.1 (GND). (Fig. 35).
3) Adjust VR902 so that the DC voltmeter indicates + 20
mV + 2 mV.
DC Voltmeter
TP. 3
(TER)
TP. 1
(GND)
Fig. 35
3. Error rate check
Put the error rate measurement disc into the PLAY mode,
connect the frequency counter to TP. 5 (TC 1) and TP. 1
(GND), and measure the error rate.
Measurement scale is Hz/sec.
Note) Carry out error rate check after confirming that the
counter value is 7.35 kHz when the unit is in the STOP
mode.
4. Inspecting the Actuator (Fig. 41a)
Check the resistance of the Actuator Coils. If the values
are as follows the condition is normal:
Focus Coil dence eee cece cence eee e ese aee sere sceeessesene 30 a (Ohms)
Tracking Coil vcrrrcccceeetseeeeeeseettertee ee teteees 102 (Ohms)
If any coil is open or short circuited, the actuator may be
defective. Check that the lens moves with a 1.5V dry cell.
AF Direction |
Fig. 36
SECTION LECTEUR CD
Lors des réglages de la plaquette de circuits imprimés PX,
enlever la plaquette de circuits imprimés de clés et, apres
avoir branché un calibre de réglage sur le point test (se
référer a Démontage Fig. 7), placer un disque dans I’unité
et effectuer les réglages ensuite.
Plaquette de circuits imprimés PX
Méthode de réglage 9: 37
Lorsqu’une quelconque des opérations ci-dessous est effec-
tuée, veiller a faire les réglages de circuit décrits aux
sections 1-3 ci-dessous.
(1) Remplacement et démontage des piéces de I’ensemble
du mécanisme de I’unité.
(2) Remplacement des piéces dans I'unité de téte de lecture.
(3) Remplacement des piéces dans le circuit d’alimentation
CD.
Réglage du circuit du lecteur CD
Note: Si le réglage est fait aprés le remplacement des piéces
de l’unité de téte de lecture, prérégler la résistance
variable comme indiqué sur la table ci-dessous.
@ Préréglage
: Numéro
Réglage nee
du circuit
Sortie de diode laser VR901
Décentrage de servo
; VR902
de lecture de piste
Les réglages doivent étre effecturés dans l|’ordre suivant.
Plaquette de circuit imprimés PX
J74
GFS e—e
OC ie
o—* WFCK
TP.5(TC1)@ @TP. 4 (GND) VR901 Réglage de sortie
de diode laser
TP. 3(TER)@ © | [Rédese dkcorage 7
p 1c901 | Reglage de decentrage
TP. 2 (EFM)@ ©- de servo de lecture de piste
@ TP. 1 (GND)
D 1¢908
oO
Fig. 38
Précautions pour le fonctionnement CD
Mettre hors tention I’unité CD du MX-W50, sauf pour la
fonction CD (néanmoins, le IC 907 reste sous tension).
ll vous faut donc effectuer les opérations suiva ntes lorsque
vous réglez séparément la plaquette de circuits imprimés
PX.
—18—