Sharp QT-CD111 Service Manual page 19

• 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. 19-1, 2)?
Yes
Check the tracking system.
HF
0.1V/DIV
0.5µsec/DIV(DC)
(When playing
back the disc)
Figure 19-1
• Check the tracking system.
Check waveform of IC801 pin 7 (TE).
The waveform shown in Fig. 19-3
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
Although IL is possible,
Yes
play is impossible.
Check the VCO-PLL system.
Yes
5ms
1.00 V
IC801 7 TE
5 ms
5.0 V
IC801 54 DRF
Figure 19-3
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
– 19 –
QT-CD111/111C
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 19-2
Check the periphery of IC801
Yes
pin 8 to pin 15, and IC804 to
BI801/CNS801.
Check the periphery of
IC801 pin 14.
Yes