Service Manual

Adjustment Preparation
Apply markings to the positions of the variable resistors
before adjustment.
If the adjustment are out of the
specifidtions, the following symptoms may occur.
[Focus gain]
If the focus adjustment is too low the pickup lens will not
be able to focus properly and the disk will not rotate.
If the
adjustment
is too high portions of a track may be skipped
and noise will increase.
[Tracking gain]
If the tracking adjustment is too low the drive is more
susceptable to shocks
or bumps, portions of a track may be
skipped or the disk time counter may stop.
If the adjustment is too high the pickup lens may oscillate
leading to unstable
or distorted sound.
The focus and tracking adjustments are done so as to
mutually satisfy conflicting characteristics.
6-3. Test equipment and tools
necessary for adjustment
I. Oscilloscope
2. DC voltmeter
3. Non-metallic adjustment screwdriver
4.
Test CD (A-BEC TCD-792A)
6-4. CD Drive Unit Adjustment Proce-
dure
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Fig. 6-2
Oscilloscope
Fig. 6-3
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Fig. 6-1
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6-4-1. FE (Focus Error) bias adjustment
and focus gain adjustment
I. Connect the oscilloscope to test point FE IN as
shown
in Fig. 6-2.
2. Turn the power switch on and set the CD drive to
the stop mode.
3. Adjust Rll4 (FE bios) so the DC voltage at the
test point (FE IN)
is OV.
4. Play the first track of the test CD and adjust
Rill (Focus gain) so the DC voltage is - 7mV.
6-4-2. FE balance and tracking gain
adjustments
I. Connect the oscilloscope to test point BP IN as
shown
in Fig. 6-3.
2. Turn the power switch on and play the first track
of the test CD.
3. After play has begun, connect the
TEST pin to
GND.
4. Adjust RI04 (FE balance) so the center voltage
of the waveform is OV.
5. Adjust Rll3 (tracking gain) so the amplitude of
the wavefonn is 0.4V as in Fig. 6-4.
Fig. 6-4
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