Sony HCD-GP7 Service Manual page 20

HCD-GP7
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CD SECTION
Note:
1. CD Block is basically designed to operate without adjustment. There-
fore, 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 10MΩ 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.
S-curve Check
Connection:
CD board
TP4 (FE)
TP7 (DVC)
Procedure:
1. Connect an oscilloscope to test point TP4 (FE) and TP 7(DVC)
on the CD board.
2. Turn the power on.
3. Put the disc (YEDS-18) in and turned power switch on again
and actuate the focus search. (actuate the focus search when
disc table is moving in and out)
4. Check the oscilloscope waveform (S-curve) is symmetrical
between A and B. And confirm peak to peak level within 2.4 ± 1 Vp-p.
S-curve waveform
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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
brightness to obtain best waveform.
Checking Location: CD board (SIDE B)
(See page 21)
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oscilloscope
+
–
symmetry
A
within 2.4 ± 1 Vp-p
B
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8
RFAC Level Check
Connection:
CD board
TP5 (RFAC)
TP7 (DVC)
Procedure:
1. Connect an oscilloscope to test point TP5 (RFAC) and TP
7(DVC) on the CD board.
2. Turn the power on.
3. Put the disc (YEDS-18) in to playback the number five track.
4. Confirm that oscilloscope waveform is clear and check RFAC
signal level is correct or not.
Note: A clear RFAC signal waveform means that the shape "◊" can be
clearly distinguished at the center of the waveform.
RFAC signal waveform
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3 6 7 1 3 1 5
Checking Location: CD board (SIDE B)
(See page 21)
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oscilloscope
+
–
VOLT/DIV: 200 mV
TIME/DIV: 500 ns
level: 0.9 ± 0.4 Vp-p
0 5 8 2 9 9 4 2 8
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