Yamaha GX-900 Service Manual page 36

MECHANISM ADJUSTMENT
When making adjustment, be sure to connect an extension cable for servicing and an expansion P.C.B. as shown in
Fig.29.
1. Optical pickup rating inspection method
(Externally attached)
GND (TP1125)
IC1101 No.43 pin
100K
EOUT (TP1129)
IC1101 No.26 pin
470p
470p
FOUT (TP1130)
100K
IC1101 No.25 pin
(See page 69)
After performing automatic adjustment in the AUTO mode
selected from the test mode by using a high reflecting MD
disc (COMPLETE status on display), adjust the EOUT to
FOUT Lissajous waveform (x-y).
1. Loosen 3 screws of the spindle motor a little and make
adjustment while watching the Lissajous waveform.
2. After adjustment, tighten screws in the order of (q), (w)
and (e).
2. Jitter verification method
After performing automatic adjustment in the AUTO mode
selected from the test mode by using a low reflecting MD
disc, confirm the jitter in the pit continuous reproduction
mode and the groove continuous reproduction mode.
FFC for 5P extension
TX946190
CN1300(Rear face)
CN1602(Rear face)
CN1601(Rear face)
CN1603(Rear face)
CN1604(Rear face)
MD Main P.C.B.
Connector for 6P-2P extension
TX946210
35
Oscilloscope
GND CH1 CH2
b
X Y
Lissajous waveform
a:b = Within 4:1
Fig. 26
Connector for 2P extension
TX946200
From motor
Mechanism
SW P.C.B.
FFC for 28P extension
TX946220
CN1101
a
Spindle motor
Adjustment hole
3
Spindle motor
1
Adjustment hole
2
IC1201 No.1 pin (TP1201)
EFMMON
GND
(TP1125)
(See page 69)
From magnetic head
Extension P.C.B. for servicing
(TX946230)
Install an Extension P.C.B. for servicing
to the mechanism.
1
3
2
Check the Lissajous wave-
form while adjusting the
installation position by using a
screwdriver in the adjustment
hole in the spindle motor.
Fig. 27
Jitter meter
Fig. 28
From optical pickup
Fig. 29