LG CJ87 Service Manual page 51

NO SOUND
There is no sound output in the MIC IN function, repair the set according to the following guide.
9-4. MIC IN FUNCTION
9-4-1. Solution
Replace IC200, IC201 on MAIN board.
9-4-2. How to troubleshoot (Countermeasure)
1) Check MIC_SIG signal to pin6 of CN200.
  If no signal, check the signal to pin7 of CN3M01 on the FRONT board.
Check if the signal is entered from pin6 of CN200 to MAIN board.
2) Check if MIC_SIG is entered from pin6 of CN200 to pin2, pin13 to IC201(MIC AMP).
3) Check if the amplified signal comes out from pin3 & pin12 of IC201.
  If no signal output, check +3.3 V for IC201, replace IC201 with a new one if it has a problem.
4) Check if MCS_BCK, MCS_LRCK, & MCS_MCLK are entered from IC501 to IC200.
5) Check if ADC_DATA is entered from IC200 to IC501.
  If no signal, check +3.3 V(ADC) for IC200. If is NG, replace it a new one.
6) Check the following I2S signal flow from IC501 to IC600.
  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.
  If AMP is damaged, replace it with a new one.
9-4-3. Service hint (Any picture/ Remark)
MCS_MCLK to R219 MCS_MCLK to R219
MCS_LRCK to AR201 MCS_LRCK to AR201
MCS_BCK to AR201 MCS_BCK to AR201
ADC_DATA to AR201 ADC_DATA to AR201
< MAIN board top view >
ONE POINT REPAIR GUIDE
IC200 IC200
IC201 IC201
< MAIN board bottom view >
3-22
MIC_IN_DATA. pin2 MIC_IN_DATA. pin2
MIC_OUTPUT. pin3 MIC_OUTPUT. pin3