LG CM9750 Service Manual page 41

NO SOUND
There is no sound output in the TUNER function, repair the set according to the following guide.
10-4. TUNER FUNCTION
10-4-1. Solution
Replace IC201, TU500 on MAIN board.
10-4-2. How to troubleshoot (Countermeasure)
1) Check if TUNER_L/R is entered from pin1 & 3 of TU500 to IC201(pin26, 27).
  If no signals, Check +3.3 V for Tuner power.
  Check if the Tuner control signals (CLK, DAT, CE, RST, GPO2) are entered from IC501 to TU500.
If it doesn't work, replace TUNER with a new one.
2) Check if ADC_BCK, ADC_LRCK & DAC_MCLK are entered from IC501 to IC201.
3) Check if ADC_DATA is entered from IC201 to IC501.
  If no signal, check +5 V & +3.3 V (ADC) for IC201. If is NG, replace it a new one.
4) Check the following I2S audio signal flow from IC501 to IC202.
  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.
5) Check if the digital audio AMP block is okay.
  If AMP is damaged, replace it with a new one.
10-4-3. Service hint (Any picture / Remark)
TUNER_L/R
IC201
CS5346
MCS_MCLK ADC/MIC_DATA
MCS_BCK
IC501
MCS_LRCK
MLC3730
MIX_DATA_OUT
< TUNER function signal fl ow >
ONE POINT REPAIR GUIDE
TUNER
Jack
Board
IC202
IR AMP
IRS2092+IRF6775
PS9860
PWM
ADC/MIC_DATA to R212 ADC/MIC_DATA to R212
MCS_BCK to R213 MCS_BCK to R213
MCS_LRCK to R215 MCS_LRCK to R215
MCS_MCLK to R216 MCS_MCLK to R216
< MAIN board bottom view >
3-22
TUNER_L/R TUNER_L/R
IC201 IC201