LG BH4120SN Service Manual page 54

ELECTRICAL TROUBLESHOOTING GUIDE
Portable function.
YES
CN251 pin4, 6 audio L/R OK?
YES
IC200 pin43, 42, 41 signal OK?
YES
6A
Tuner function.
YES
TUN01 pin1, 2, 3, 4 signal OK?
YES
TUN01 pin7, 8 audio L/R OK?
YES
IC200 pin42 signal OK?
YES
6A
NO
Check CN251 and JACK PCB.
NO
NO
NO
NO
2-45
Check IC200 or replace.
Check IC101 or replace.
Check TUN01 or replace.
Check IC200 or replace.