LG CM9730 Service Manual page 38

NO SOUND
There is no sound output in the MIC IN FUNCTION, repair the set according to the
following guide.
6-6. IN THE MIC IN FUNCTION
6-6-1. Solution
Please check and replace IC508, IC506 on MAIN board.
6-6-2. How to troubleshoot (Countermeasure)
1) Check MIC_SIG signal to Pin6 of CN506.
If no signal, Check the signal to Pin6 of CN3M01 on the MIC board.
Check if the signal is entered from Pin6 of CN3M01 to MAIN board.
2) Check if MIC_SIG is entered from Pin6 of CN506 to Pin3 of IC506 (MIC AMP).
3) Check if the amplified signal is entered from Pin4 of IC506.
If no signal output, check +12 V for IC506, replace IC506 with a new one if it has a problem.
4) Check if MIC_BCK, MIC_MLCK & MIC_LRCK is entered from IC501 to IC508.
Check if MIC_DATA is entered from Pin9 of IC508 to Pin7 of IC600.
If no signal, check +5 V & +3.3 V for IC508. If it is abnormal, change replace it a new one.
5) Check the following I2S signal flow from IC508 to IC600.
If there is any trouble, check the power for each IC. If the signals are abnormal, replace it a new one.
6) 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.
6-6-3. Service hint (Any picture / Remark)
MIG_SIG
IC508
AK5358
DAC_MCLK MIC_I_DATA
IC501
MLC3700
< MIC IN function signal fl ow >
ONE POINT REPAIR GUIDE
MIC IN
IC506
MIC
S4308
Board
DAC_BCK
IC600
IR AMP
DAC_LRCK
PS9854
IRS2092+IRF6775
PWM
3-21
< Signal check point >