Sony CFD-980 Service Manual page 19

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Focus Bias Adjustment
Adjustment Location : MAIN board (Component side)
This check is to be done when the optical block replaced.
Adjustment Procedure:
1. Connect the oscilloscope to test point TP (VC) and TP (RFO)
on MAIN board.
2. Put the set into test mode.
3. Opitical pick-up setting to the center by + or – button pushing.
4. Insert disk (YEDS-18) and press ^ button.
5. Press the MODE button. (Tracking servo ON)
6. Adjust RV701 so that the oscilloscope wavewform 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 test mode after adjustment is completed.
• RF signal reference waveform (eye pattern)
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L 13942296513
When observing the eye pattern, set the oscilloscope for AC range
and raise vertical sensivity.
[MAIN BOARD] (Component side)
TP(TO)
TP(VC)
TP(FO)
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(See page 21)
VOLT/DIV : 0.2V
TIME/DIV : 500ns
+0.2
1.3 Vp-p
–0.3
Osillloscope
(DC range)
TP(FO)
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+
–
TP(VC)
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8
4-4. REFERENCE
Focus/Tracking Gain Adjustment
Adjustment Location : MAIN board (Component side)
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, it is more susceptible to 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
CD ^ or automatic
selection (0 , ) buttons
pressed). (Normally takes
about 2 seconds.)
• Music does not start and disc
continues to rotate for STOP
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CD ^ or automatic
3 6 7 1 3 1 5
selection (0 , ) buttons
pressed.)
• Sound is interrupted during
PLAY. Or time counter
display stops progressing.
• More noise during 2-axis
device operation.
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.
— 19 —
9 4 2 8
Gain
Focus
low
—
0 5 8 2 9 9 4 2 8
—
high
m
9 9
(See page 21)
Tracking
low or high
low
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low
high