LG CJ87 Service Manual page 52

NO SOUND
There is no sound output in the Bluetooth function, repair the set according to the following guide.
9-5. BLUETOOTH FUNCTION
9-5-1. Solution
Replace IC501 on the MAIN board or bluetooth module on the FRONT Panel.
9-5-2. How to troubleshoot (Countermeasure)
1) Check BT_RX, BT_TX signal to pin4, pin6 of CN504.
  If no signal, check the signal to pin4, pin6 and pin10 (+3.3 V) of on the Bluetooth module and cable
connection state.
  If there are no signal out from module, replace new module.
2) Check if BT_RX/ TX is entered from pin4, pin6 of CN504 to pin K1, pin L1 to IC501(DSP).
3) Check if MCS_BCK, MCS_LRCK & MIX_DATAN is entered from IC501 to IC202.
  If no signal, check VCC12(+1.2 V) for IC501. If it is abnormal, change replace it a new one.
4) Check the following I2S signal flow from IC501 to IC202.
  If there is any trouble, check the power for each IC. If the signals are abnormal, replace it a new one.
5) Check if the digital audio AMP block is okay.
  If AMP is damaged, replace it with a new one.
9-5-3. Service hint (Any picture/ Remark)
B/T Module
BT_RX,
BT_TX
IC501
MCS_BCK
MCS_LRCK
MIX_DATA_OUT
IC600
PWM
< MAIN board bottom view >
ONE POINT REPAIR GUIDE
IR AMP
3-23
BT_TX. pin4 BT_TX. pin4
BT_RX. pin6 BT_RX. pin6
BT_RTS. pin7 BT_RTS. pin7
BT_CTS. pin8 BT_CTS. pin8
BT_TX. R519 BT_TX. R519
< MAIN board top view >
CN500 CN500
BT_RTS. R51D BT_RTS. R51D
BT_RX. R51B BT_RX. R51B
BT_CTS. R512 BT_CTS. R512