Sharp MD-C2 Service Manual page 69

• The CD operation keys work.
Check the FOCUS-HF system.
Playback can be performed without a disc.
Yes
Does the pickup move up and down two twice?
Yes
Does the output waveform of IC1 pin 16 (FD) match that
shown in Figure 69-1?
Yes
Check 4 MHz of IC1 pin 50 (CLK) line and the microcomputer
data of pin 51 (CL), pin 52 (DAT) and pin 53 (CE).
• Playback can only be performed when disc is
loaded.
Is the Focus servo active? (Can you hear it working?)
Yes
Does the DRF signal of IC1 pin 54 change from "L" to "H"?
Yes
Is HF waveform normal (see the Figure 69-2, Figure 69-3.)?
Yes
Check the tracking system.
HF
1.0V/DIV
0.5µsec/DIV(DC)
(When playing
back the disc)
Figure 69-2
Focus search OK
No
Check the area around IC3 to CNP2.
No
0.5s
0.50 V
IC1 16 FD
0.5s
0.50 V
IC1 7 TE
Check the laser diode driver.
No
Check the area around IC1 pin 16 to pin 21 (focus servo circuit).
If the disc is not turning, the
No
DRF should not change to
"H".
Level is abnormal
No
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
– 69 –
MD-C2
Focus search is
performed two
times when play
operation is done
without disc.
1
2
Figure 69-1
Check the spindle system.
Check the periphery of
IC1 pin 41 and pin 42.
Check the spindle system.
Waveform in case of
normal play-back
2
1
3
4
Figure 69-3