Playback Can Only Be Performed When A Disc Is Loaded; Check The Tracking System - Sharp CDC2900 - 3-CD Compact Stereo System Service Manual

• 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.45-1, 2)?
Yes

Check the tracking system.

HF
1.0V/DIV
0.5 sec/DIV(DC)
(When playing
back the disc)
Figure 45-1
• Check the tracking system.
Check waveform of IC1 pin 7 (TE).
The waveform shown in
Fig.45-3 appears, and no-
disc state appears soon.
Play is possible in
TEST mode.
Data cannot be read.
Tracking servo is
inoperative.
Yes
Although IL is possible,
Yes
play is impossible.
Yes
5ms
1.00 V
IC1 7 TE
5 ms
5.0 V
IC1 54 DRF
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
Check the periphery of IC 1
pin 8 to pin 15, and IC 5 to
Yes
CNP2.
Normal jump is impeded,
Yes and the program top
cannot be reached.
Check the VCO-PLL system.
Figure 45-3
– 45 –
CD-C622/C2900
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 45-2
Check the periphery
of IC 1 pin 14.
Yes
4
3