— 12 —
Focus bias Check
Condition:
• Hold the set in horizontal state.
Check Procedure:
1. Set the equipment to service mode stop state. (See page 10.)
2. Connect the oscilloscope to the test point TP522 (RF) of the
CD board.
3. Move the optical pick-up by pressing the + and = keys.
4. Put the disc (YEDS-18).
5. Press the ^ key.
From focus searching, focus is turned ON while entering
CLV drawing-in mode. Tracking and sled are turned OFF.
6. Press the PLA Y MODE key. (Both tracking and sled are turned
ON.)
7. Check the oscilloscope waveform is as shown below.
A good eye pattern means that the diamond shape (≈) in the
center of the waveform can be clearly distinguished.
RF SIGNAL REFERENCE WAVEFORM (EYE PATTERN)
8. Stop revolving of the disk motor by pressing the p key.
9. After the completion of adjustment, reset service mode. (See
page 10.)
Check Location: CD board (See page 14.)
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Focus/Tracking Gain Adjustment
A servo analayzer is necessary in order to perform this adjustment
exactly.
However, this gain has a margin, so even if it is slightly off,
there is no problem. Therefore, do not perform this adjustment.
Focus/tracking gain determines the pick-up follow-up relative to
mechanical noise and mechanical shock when the 2-axis device
operates. However, as these reciprocate, the adjustment is at the
point where both are satisfied.
• When gain is rased, the noise when 2-axis device operates
increase.
• When gain is lowered, it is more susceptible to mechanical shock
and skipping occurs more easily.
This adjustment has to be performed upon replacing any of the
following parts.
• Optical pick-up
• RV503 (Focus gain VR)
• RV502 (Tracking gain VR)
Normally, be sure not to move RV503 (focus gain VR) and
RV502 (tracking gain VR).
Adjustment method:
– Focus Gain Adjustment –
This adjustment is not performed.
If focus gain VR RV503 is turned, set to mechanical center.
– Tracking Gain Adjustment –
(perform at normal operation)
1. Place the optical pick-up level, horizontally. (If the optical pick-
up is not level, the 2-axis device will be weighted and adjustment
cannot be done.)
2. Connect the oscilloscope TP536 (TE) and TP520 (VC) on CD
board.
3. Set the disk (YEDS-18) and press the ( (+) key.
4. Turn R V502 slightly clockwise (tracking gain drops) and obtain
a waveform with a fundamental wave (waveform has large
waves) as in Figure 1.
5. Turn R V502 slowly counterclockwise (tracking gain rises) until
the fundamental wave disappears (no large waves) as in Figure
2.
6. Set R V502 to the position about 30° counterclockwise form the
position obtained in step 5. If RV502 contact point is more than
90° 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
waveform. Check that no traverse waveform appears for both
( (+) or = key and observe the 100 track jump
waveform. 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.