Sharp CD-C250X BK Service Manual page 13

Is there following voltage input in specific state of IC701 pin 8' 7
Close state: OV
Intermediate state between open state and close state: 5V
Is H output to IC701 pin 70 or 71 for 5 seconds when the OPEN/
CLOSE key is pressed?105 is defective. Replace it.
Is 4V output between IC901 pins 3 and 7 during operation stated
above?
Check the CD, DPS microcomputer, power supply, 4.19 MHz and
16.93 MHz clock, and reset terminal.
Check the waveform of SCK, SO (DATA) and SI (COMM).
(Fig. 14-l-5)
See if the pick-up is in the pick-up in SW4 position.
If the items mentioned above are OK, check the main
microcomputer IC701.
Yes
Yes
Yes
Yes
Yes
Yes
Check the SW1 and the wiring from the IC701 pin 8 to the SWl.
Check the wiring of the lC701 pins 70 and 71, IC901 pins 1
and 9.
Check the periphery of IC901.
OK
I