LG CM9730 - Page 38

3-21
ONE POINT REPAIR GUIDE
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)
tpjzpnUGGXMYG
tpjpkh{hUGwpuG`
tpjsyjrUGwpuGXW
tpjtjsrUGwpuXX tpjijrUGw puGXY
IC501
MLC3700
IC600
PS9854
PWM
DAC_BCK
DAC_L RCK
IC508
AK5358
MIC IN
MIC_I_DATADAC_MCLK
MIC
Board
MIG_SIG
IC506
S4308
IR AMP
IRS2092+IRF6775
< Signal check point >
< MIC IN function signal fl ow >