Sony CFD-CD777SMK2 Service Manual page 16

CFD-CD777SMK2
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Focus Bias Adjustment
This adjustment is to be done when the optical pick-up is replaced.
Procedure:
MAIN board
Solder bridge (FOCUS)
TP (VC)
1. Connect the oscilloscope to solder bridge (FOCUS) and TP
(VC) on the MAIN board.
2. Put the set into test mode. (See page 24.)
3. Optical pick-up setting to the center by > or . button
pushing. (Move the optical pick-up to the music area on the
disc to enable easy visibility of the eye pattern.)
4. Put the disc (YEDS-18) and press NX button.
From focus searching, focus is turned ON while entering
CLV drawing-in mode. Tracking and sled are turned OFF.
5. Press the NX button.
[Both tracking and sled are turned ON.]
6. 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.
7. Release the test mode after adjustment is completed.
• RF signal reference waveform (eye pattern)
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L 13942296513
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.
Adjustment Location: MAIN board (See page 18)
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oscilloscope
(AC range)
+
–
1.2 ± 0.2 Vp-p
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8
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
STOP → NX button or automatic selection.
(., > buttons pressed.)
(Normally takes about 2 seconds.)
• Music does not start and disc continues to
rotate for STOP → NX button or automatic
selection.
(., > buttons pressed.)
• Sound is interrupted during PLAY.
Or time counter display stops progressing.
• More noise during 2-axis device operation
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The following is a simple adjustment method.
– Primary Adjustment –
Note: Since exact adjustment cannot be performed, remember the posi-
tions of the controls before performing the adjustment. If the posi-
tions after the primary adjustment are only a little different, return
the controls to the original position.
Connection:
Solder bridge (TRACKING)
Solder bridge (FOCUS)
TP (VC)
co
.
9 4 2 8
Gain
Focus Tracking
low
low or
high
– low
– low
high high
0 5 8 2 9 9 4 2 8
oscilloscope
(DC range)
+
–
m
9 9
9 9