Sony PMC-D307L Service Manual page 15

Focus Bias Adjustment
This adjustment is to be done when the optical pick-up is replaced.
Procedure:
CD board
TP (RF)
TP (VC)
1. Connect the oscilloscope TP (RF) and TP (VC) on the CD board.
2. Insert the disc (YEDS-18) in and close the lid for CD.
3. Put the set into test mode. (See page 14.)
4. Press + and = buttons to move the optical pick-up to the
center. (Move the optical pick-up to the music area on the disc
to enable easy visibility of the eye pattern.)
5. Press the ( button.
From focus searching, focus is turned ON while entering
CLV drawing-in mode. Tracking and sled are turned OFF.
6. Press the ( button.
[Both tracking and sled are turned ON.]
7. Adjust RV701 so that the oscilloscope waveform is as shown in
the figure below. (eye pattern)
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)
VOLT/DIV : 0.2 V (With the 10:1 probe in use)
TIME/DIV : 500 ns
When observing the eye pattern, set the oscilloscope for AC
range and raise vertical sensitivity.
8. Release the test mode after adjustment is completed.
Adjustment Location: CD board (See page 17.)
oscilloscope
(AC range)
+
–
1.3 ± 0.2 Vp-p
REFERENCE
Focus/Tracking Gain Adjustment
A frequency response analyzer 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 (vertical and
horizontal) relative to mechanical noise and mechanical shock when
the 2-axis device operate.
However, as these reciprocate, the adjustment is at the point where
both are satisfied.
• When gain is raised, the noise when the 2-axis device operates
increases.
• When gain is lowered, mechanical shock and skipping occurs
more easily.
• When gain adjustment is off, the symptoms below appear.
Symptoms
• The time until music starts becomes
longer for p→( on automatic
selection.
(=, + buttons pressed.)
(Normally takes about 2 seconds.)
• Music does not start and disc
continues to rotate for p→( or
automatic selection.
(=, + buttons pressed.)
• Sound is interrupted during PLAY.
Or time counter display stops
progressing.
• More noise during 2-axis device
operation.
– 15 –
Gain
Focus Tracking
low low or high
— low
— low
high high