Sharp CDC2900 Service Manual - Page 45

Playback can only be performed when a disc is, loaded., Check the tracking

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Page 45 highlights

CD-C622/C2900 • 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. Check the laser diode driver. No Check the area around IC1(16) - (21) (focus servo circuit). Yes If the disc is not turning, the DRF No should not change to "H". Check the spin system. No Level is abnormal. Yes Check the periphery of IC1 pins 41 and 42. Waveform is unstable. Yes Check the spin system. HF 1.0V/DIV 0.5µsec/DIV(DC) (When playing back the disc) Figure 45-1 • Check the tracking system. 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 Waveform in case of normal play-back 2 1 3 4 Figure 45-2 Check waveform of IC1 pin 7 (TE). The waveform shown in Tracking servo is Check the periphery of IC 1 Fig.45-3 appears, and no- Yes inoperative. Yes pin 8 to pin 15, and IC 5 to disc state appears soon. CNP2. Play is possible in TEST mode. Although IL is possible, Yes play is impossible. Yes Normal jump is impeded, and the program top Yes cannot be reached. Data cannot be read. Check the VCO-PLL system. Yes Check the periphery of IC 1 pin 14. 5ms 1.00 V IC1 7 TE 4 5 ms 5.0 V IC1 54 DRF 3 Figure 45-3 - 45 -

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– 45 –
CD-C622/C2900
•
Playback can only be performed when a disc is
loaded.
Is HF waveform normal (see the Fig.45-1, 2)?
Check the tracking system.
Is the Focus servo active? (Can you hear it working?)
Check the laser diode driver.
Check the area around IC1(16) - (21) (focus servo circuit).
No
Yes
Yes
Yes
Does the DRF signal change from "L" to "H"?
No
Yes
If the disc is not turning, the DRF
should not change to "H".
Level is abnormal.
No
Yes
Waveform is unstable.
Check the spin system.
Yes
Check the periphery of
IC1 pins 41 and 42.
Check the spin system.
Figure 45-2
Figure 45-1
Waveform in case of
normal play-back
HF
1.0V/DIV
0.5
μ
sec/DIV(DC)
(When playing
back the disc)
3
2
1
4
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 tracking system.
Check waveform of IC1 pin 7 (TE).
Play is possible in
TEST mode.
Although IL is possible,
play is impossible.
Check the periphery
of IC 1 pin 14.
Normal jump is impeded,
and the program top
cannot be reached.
Check the periphery of IC 1
pin 8 to pin 15, and IC 5 to
CNP2.
The waveform shown in
Fig.45-3 appears, and no-
disc state appears soon.
Tracking servo is
inoperative.
Yes
Yes
Yes
Yes
Yes
Data
cannot be read.
Check the VCO-PLL system.
Yes
3
4
5ms
1.00 V
IC1
7
TE
5 ms
5.0 V
IC1
54
DRF
Figure 45-3