Focus/Tracking Gain AdjustmentThe waveforms are those measured with the oscilloscope set as
A servo analayzer is necessary in order to perform this adjustmentshown below.
exactly.Y VOLT/DIV: 500 mV
However, this gain has a margin, so even if it is slightly off,Y TIME/DIV: 5 ms
there is no problem. Therefore, do not perform this adjustment.Y Waveform when tracking gain is lowered.
Focus/tracking gain determines the pick-up follow-up relative toFundamental wave appears (large waves).
mechanical noise and mechanical shock when the 2-axis device
operates. However, as these reciprocate, the adjustment is at the
��� 0 V
point where both are satisfied.
Y When gain is rased, the noise when 2-axis device operates in-
crease.Fig. 1
Y When gain is lowered, it is more susceptible to mechanical shock
and skipping occurs more easily.Y Waveform when fundamental wave disappears (no large waves).
This adjustment has to be performed upon replacing any of the
following parts.
Y Optical pick-up��� 0 V
Y RV503 (Focus gain VR)
Y RV502 (Tracking gain VR)Fig. 2
Normally, be sure not to move RV503 (focus gain VR) and
RV502 (tracking gain VR).Y Waveform with no traverse waveform during 100 track jump.
(Brake application is smooth because of adjustment.)
Adjustment method:
� Focus Gain Adjustment �
��� 0 V
This adjustment is not performed.
If focus gain VR RV503 is turned, set to mechanical center.
� Tracking Gain Adjustment �
(perform at normal operation)
oscilloscope100 track jump waveform
(DC range)
Fig. 3
MAIN board
10 k WY Waveform with traverse waveform during 100 track jump.TAP805 (TE)+
(Brake application is poor because of adjustment.)
TP520 (VC)�
0.0022 ?F
(See page 13)
1. Place the optical pick-up level, horizontally. (If the optical
pick-up is not level, the 2-axis device will be weighted and��� 0 V
adjustment cannot be done.)
2. Connect the oscilloscope to TAP805 (TE) and TP520 (VC) on
MAIN board.
3. Set the disc (YEDS-18) and pr^ keess the y.
4. Turn RV502 slightly clockwise (tracking gain drops) and ob-
tain a waveform with a fundamental wave (waveform has large
waves) as in Figure 1.100 track jump
5. Turn RV502 slowly counterclockwise (tracking gain rises) untilwaveformtraverse waveform
the fundamental wave disappears (no large waves) as in Fig-Fig. 4
ure 2.
6. Set RV502 to the position about 30u counterclockwise form
the position obtained in step 5. If RV502 contact point is more
than 90u counterclockwise from mechanical center, tracking
gain is too high. In this case, readjust from step 4.
7. Press + or = key and observe the 100 track jump wave-
form. Check that no traverse waveform appears for both +
or = directions. (See Figures 3 and 4.) It is acceptable if
the traverse waveform appears only now and then, but if it
appears constantly, raise tracking gain slightly and check step
7 again.
8. Check that there is not abnormal amount of operation noise
(white noise) from the 2-axis device. If there is, tracking gain
is too high, readjust starting with step 4.
� 12 � |
ACEC
