Sharp CD-C422 Service Manual page 33

• When the CD tray fails to open or close.
Is there following voltage input in specific state of IC701 pin 19?
Open state: 0V
Close state: 0V
Intermediate state between open state and close state: 4.3V
Yes
Is H output to IC2 pin 24 or 25 for 7 seconds when the OPEN/
CLOSE key is pressed?IC91 is defective. Replace it.
Yes
Is 4V output between IC91 pins 3 and 7 during operation
stated above?
Yes
Check the loading motor (M1) and the loading mechanism.
• The CD function will not work.
The CD operating keys don't work.
Yes
Check the CD, DSP, power supply, and 16.93 MHz clock, and
reset terminal.
Yes
Check the waveform of SCK, SO (DATA) and SI (COMM).
Yes
See if the pick-up is in the PICKUP IN SW position.
If the items mentioned above are OK, check the main
microcomputer IC701.
• The CD operating keys work.
Check the Focus - HF system.
Playback can be performed without a disc.
Yes
Does the pick-up move up and down twice?
No
Does the output waveform of IC1(16)(FD) match that shown in
Fig. 33?
No
Check the IC1(50)(CLK) line, 4MHz.
Check the microcomputer data on pins (51)(CL), (52)(DAT)
and (53)CE.
Yes
CD-C422/C422C/C2800/C2800C
Check the OPEN CLOSE SW and the wiring from the IC701
No
pin 19 to the OPEN CLOSE SW.
Check the wiring of the IC2 pins 24 and 25, IC91 pins 1 and 3.
No
IC2 defective.
Check the periphery of IC91.
No
IC91 defective.
0.5s
0.50 V
IC1 16 FD
0.5s
0.50 V
IC1 7 TE
Focus search OK
Yes
Check the area around IC5-CNP2.
Yes
– 33 –
OK
OK
Focus search is
performed two
times when play
operation is done
without disc.
1
2
Figure 33