Toshiba SD-K740SU Service Manual page 38

TROUBLESHOOTING GUIDE
NO OPTICAL OUT
Is there voltage at pin
2 of OS8001 about 5V?
Yes
Is the waveform at pin 1
of OS8001 about 3V ?
No
Change OS8001.
No
Yes
D-7
Check P.CON +D5V line.
Refer to "NO DIGITAL
AUDIO ON PLAYBACK OF
COXIAL JACK".