LG OK99 Service Manual page 33

NO BOOTING IN CD/USB FUNCTION
After you turn on power key and displayed message in the following order (HELLO  VOL XX  CD
or USB) on VFD, it will not display other message on VFD, and it will not boot-up normally.
4-3. SERIAL FLASH (IC503)
4-3-1. Solution
Please check and replace IC503 on MAIN board.
4-3-2. How to troubleshoot (Countermeasure)
1) If the crystal(X500) does oscillate, check Serial Flash(IC503) on MAIN board.
 Check pin8(VCC), pin6(SCLK), pin1(CS), pin2(SO), pin5(SI) of below waveform.
2) If pin8, 6, 1, 2, 5 doesn't come out, check damping resistor(R5B72, R5B73, R5B74, R5B76) of IC503.
 If damping resistor of IC503 is OK, then replace IC503. (it need to download program)
3) After change IC503, if It is still not below waveform, check IC501(DSP IC).
4-3-3. Service hint (Any picture / Remark)
IC503 IC503
< MAIN board bottom view >
ONE POINT REPAIR GUIDE
V V CC
CS#
SCLK
SO SO
< Signal waveform >
3-8
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