Sharp CD-PC1881V Service Manual page 42

CD-PC1881V
• The CD operating keys work.
Check the Focus - HF system.
Playback can be performed without a disc.
Yes
Does the pick-up move up and down twice?
No
Does the output waveform of IC1(16)(FD) match that shown in
Fig. 42-1?
No
Check the IC1(50)(CLK) line, 4MHz.
Check the microcomputer data on pins (51)(CL), (52)(DAT)
and (53)CE.
• Playback can only be performed when a disc is
loaded.
Is the Focus servo active? (Can you hear it working?)
Yes
Does the DRF signal change from "L" to "H"?
Yes
Is HF waveform normal (see the Fig. 42-2, 3)?
Yes
Check the tracking system.
HF
1.0V/DIV
0.5µsec/DIV(DC)
IC1 41
(When playing
back the disc)
Figure 42-2
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Focus search OK
Yes
Check the area around IC3-CNP2.
Yes
0.5s
0.50 V
IC1 16 FD
0.5s
0.50 V
IC1 7 TE
Check the laser diode driver.
No
Check the area around IC1(16) - (21) (focus servo circuit).
If the disc is not turning, the DRF
No
should not change to "H".
No
Level is abnormal.
Waveform is unstable.
0.5s
1.00 V
IC1 16 FD
0.5s
10.0 V
IC2 13 CLV+
0.5s
10.0 V
IC1 54 DRF
0.5s
2.00 V
IC1 7 TE
– 42 –
Focus search is
performed two
times when play
operation is done
without disc.
1
2
Figure 42-1
Yes
Check the spin system.
Yes
Check the periphery of
IC1 pins 41 and 42.
Yes
Check the spin system.
Waveform in case of
normal play-back
2
1
3
4
Figure 42-3