LG OM4560 Service Manual page 28

5. NO SOUND
There is no sound output in the CD FUNCTION, repair the set according to the following guide.
5-1. IN THE CD FUNCTION
5-1-1. Solution
Please check and replace IC502, IC700 on MAIN board.
5-1-2. How to troubleshoot (Countermeasure)
1) Check CD_BCLK, CD_LRCK, & CD_DOUTA signals from IC401 to IC502.
  If no signal, check if the RF & servo signals from MD is entered to IC401.
Refer to the "No operation of MD" guide on Item 4.
2) Check the following I2S signal flow. < I2S audio signal Interface >
- MCS_BCK : IC502_Pin E1 --> IC700_Pin23
- MCS_LRCK : IC502_Pin D1 --> IC700_Pin22 (44.1 kHz)
- MCS_DATA : IC502_Pin E2 --> IC700_Pin24
  If there is any trouble, check the power for each IC.
The power is normal but, if the signal waveform to the IC is distorted or no signal, replace it with a new one.
3) Check if "Digital audio AMP block" on Item 5-2 is normal.
5-1-3. Service hint (Any picture/ Remark)
ONE POINT REPAIR GUIDE
3-11
< I2S Signal Flow >
< Waveform of I2S audio interface signals >