LG CM5660 Service Manual page 25

4. 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 (IC501)
4-3-1. Solution
Please check and replace IC501 on MAIN board.
4-3-2. How to troubleshoot (Countermeasure)
1) If the crystal (X500) does oscillate, check serial flash (IC501) on MAIN board.
  Check pin8 (VCC), pin6 (CLK), pin1 (CS), pin2 (DO), pin5 (DI) of below waveform.
2) If pin1, 2, 5, 6 doesn't come out, check registers (R595, R596, R570, R571, R572, R569) of IC501.
  If registers of IC500 is OK, then replace IC500. (it need to download program.)
3) After change IC500, if It is still not below waveform, check IC500 (DSP IC).
4-3-3. Service hint (Any picture/ Remark)
< MAIN board top view >
ONE POINT REPAIR GUIDE
IC501 IC501
V V CC
CS#
CLK
DO
< Signal waveform >
3-8