LG CM9730 Service Manual page 36

NO SOUND
There is no sound output in the PORT. IN FUNCTION, repair the set according to the
following guide.
6-4. IN THE PORT. IN FUNCTION
6-4-1. Solution
Please check and replace IC202 on MAIN board.
6-4-2. How to troubleshoot (Countermeasure)
1) Check PT_L/R signal from JOG board to MAIN board.
2) Check if PT_LR is entered Pin4 & 5 of CN3J01
3) Check POT_L/R signals to IC202(Pin21, 22).
4) Check if ADC_BCK, ADC_LRCK, & DAC_MCLK are entered from IC501 to IC202.
5) Check if ADC_DATA is entered from IC202 to IC501.
If no signal, check +5 V & +3.3 V(ADC) for IC202. If is NG, replace it a new one.
6) Check the following I2S signal flow from IC501 to IC600. (Refer to Item 6-1.)
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.
7) Check if the digital audio AMP block is okay. Refer to "Digital Audio AMP" guide.
If AMP is damaged, replace it with a new one.
6-4-3. Service hint (Any picture / Remark)
POT_L/R
IC202
CS5346
DAC_MCLK ADC_DATA
DAC_BCK
IC501
DAC_LRCK
MLC3700
< PORT. IN function signal fl ow >
ONE POINT REPAIR GUIDE
POT. IN
VOLUME
Board
IC600
IR AMP
PS9854
IRS2092+IRF6775
PWM
Pin4 & 5 of CN3V02
3-19
Pin21 & 20 of CN3V01.
< Signal check point >