Sharp QT-CD161 Service Manual page 25

• 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. 25-1, 2)?
Yes
Check the tracking system.
HF
0.1V/DIV
0.5µsec/DIV(DC)
IC801 41
(When playing
back the disc)
Figure 25-1
• Check the tracking system.
Check waveform of IC801 pin 7 (TE).
The waveform shown in Fig. 25-3
appears, and no-disc state appears
soon.
Play is possible in
TEST mode.
Data cannot be read.
1.00 V
IC801 16 FD
10.0 V
IC801 12 CLV+
10.0 V
IC801 54 DRF
2.00 V
IC801 7 TE
Yes
The unit will be initialized in
Yes
Normal mode,but it will not
playback.
Check the VCO-PLL system.
Yes
5ms
1.00 V
IC801 7 TE
5 ms
5.0 V
IC801 54 DRF
Figure 25-3
Check the laser diode driver.
Check the area around IC801(16) - (21) (focus servo circuit).
No
If the disc is not turning, the DRF
No should not change to "H".
No
evel is abnormal.
L
Waveform is unstable.
0.5s
0.5s
0.5s
0.5s
Tracking servo is inoperative.
Normal jump is impeded, and the
program top cannot be reached.
Yes
4
3
– 25 –
QT-CD161/141
Yes
Check the spin
system.
Yes
Check the periphery
of IC801 pins 41 and
42.
Yes
Check the spin
system.
Waveform in case
of normal play-
back
2
1
3
4
Figure 25-2
Check the periphery of IC801
Yes
pin 8 to pin 15, and IC803 to
BI801/CNS801.
Check the periphery of
IC801 pin 14.
Yes