Service manual

QT-CD121
– 19 –
Check the laser diode driver.
• Playback can only be performed when a disc
is loaded.
Does the DRF signal change from "L" to "H"?
No
If the disc is not turning, the DRF
should not change to "H".
Is HF waveform normal (see the Fig. 19-1, 2)?
Yes
Is the Focus servo active? (Can you hear it working?)
No
Check the area around IC801(16) - (21) (focus servo circuit).
Level is abnormal.
Check the periphery
of IC801 pins 41 and
42.
No
Waveform is unstable.
Check the spin
system.
Yes
Yes
Yes
Yes
Yes
Figure 19-2
Figure 19-1
Check the spin
system.
HF
0.1V/DIV
0.5µsec/DIV(DC)
(When playing
back the disc)
Waveform in case
of normal play-
back
3
2
1
4
0.5s
1.00 V
IC801 16 FD
0.5s
10.0 V
IC801 12 CLV+
0.5s
10.0 V
IC801 54 DRF
0.5s
2.00 V
IC801 7 TE
Check the tracking system.
▼
▼
▼
• Check the tracking system.
Check waveform of IC801 pin 7 (TE).
Check the periphery of IC801
pin 8 to pin 15, and IC804 to
BI801/CNS801.
Tracking servo is inoperative.
The waveform shown in Fig. 19-3
appears, and no-disc state appears
soon.
Yes
Yes
Yes
Yes
Play is possible in
TEST mode.
Although IL is possible,
play is impossible.
Normal jump is impeded, and the
program top cannot be reached.
Check the periphery of
IC801 pin 14.
Yes
Data cannot be read.
Check the VCO-PLL system.
Yes
3
4
5ms
1.00 V
IC801 7 TE
5 ms
5.0 V
IC801 54 DRF
Figure 19-3