The Cd Operating Keys Work; Playback Can Only Be Performed When A Disc Is Loaded - Sharp CD-PC1881V Service Manual

CD-PC1881V

• The CD operating keys work.

Check the Focus - HF system.
Playback can be performed without a disc.
Does the pick-up move up and down twice?
Does the output waveform of IC1(16)(FD) match that shown in
Fig. 42-1?
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?)
Does the DRF signal change from "L" to "H"?
Is HF waveform normal (see the Fig. 42-2, 3)?
Check the tracking system.
HF
1.0V/DIV
0.5µsec/DIV(DC)
41
IC1
(When playing
back the disc)
Figure 42-2
Yes
No
No
Yes
Yes
Yes
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