Sony SA-VA100 Service Manual page 33

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CD SECTION
Note:
1. CD Block is basically designed to operate without adjustment.
Therefore, check each item in order given.
2. Use YEDS-18 disc (3-702-101-01) unless otherwise indicated.
3. Use an oscilloscope with more than 10M impedance.
4. Clean the object lens by an applicator with neutral detergent when
the signal level is low than specified value with the following
checks.
5. Adjust the focus bias adjustment when optical block is replaced.
Focus Bias Adjustment
CD board
TP (RF)
TP (VC)
Procedure:
1. Connect oscilloscope to test point TP (RF). on CD board.
2. Turned SYSTEM POWER switch on.
3. Put disc (YEDS-18) in to playback the number two track.
4. Adjust RV101 so that the waveform is clear.
(Clear RF signal waveform means that the shape " " can be clearly
distinguished at the center of the waveform.)
5. After adjustment, check the RF signal level.
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• RF signal
VOLT/DIV: 200 mV
TIME/DIV: 500 nS
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oscilloscope
level: 1.2 ± 0.2 Vp-p
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S Curve Check
CD board
Procedure :
1. Load CDs into the each tray (seven pieces).
2. Connect oscilloscope to test point TP (FEO).
3. Connect between test point TP (FOK) and Ground by lead wire.
4. The focus search is performed by turning ON the SYSTEM
POWER.
It searches DISC 1-7 in order and stops.
5. Check the oscilloscope waveform (S-curve) is symmetrical be-
tween A and B. And confirm peak to peak level within 2.4 ± 0.7
Vp-p.
S-curve waveform
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6. After check, remove the lead wire connected in step 3.
Note: • Try to measure several times to make sure than the ratio of
A : B or B : A is more than 10 : 7.
• Take sweep time as long as possible and light up the bright-
ness to obtain best waveform.
RF Level Check
CD board
Procedure :
1. Connect oscilloscope to test point TP (RF) on BD board.
2. Turned SYSTEM POWER switch on.
3. Put disc (YEDS-18) in to playback the number two track.
4. Confirm that oscilloscope waveform is clear and check RF signal
level is correct or not.
Note: Clear RF signal waveform means that the shape " " can be
clearly distinguished at the center of the waveform.
RF signal waveform
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9 4 2 8
oscilloscope
TP (FEO)
TP (VC)
symmetry
A
within 2.4 ± 0.7 Vp-p
B
0 5 8 2 9 9 4 2 8
oscilloscope
TP (RF)
TP (VC)
VOLT/DIV: 200 mV
TIME/DIV: 500 nS
level: 1.2 ± 0.2 Vp-p
m
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