LG BH4120SN Service Manual page 46

2. NO BOOTING WHEN YOU TURN THE UNIT ON, NO MESSAGE OR
"PLEASE WAIT" ON FRONT PANEL
When you turn on your set, it will blank / no message or "PLEASE WAIT" display on front panel, and
it will not boot-up.
2-9. MAIN BOARD
2-9-1. Solution
Replace MAIN board.
2-9-2. How to troubleshoot (Countermeasure)
1) Please remove IC501 ~ IC504 and then check the Impedance between each signal (DATA, ADDRESS,
and so on.)
2) If there is some Impedance (a few Ω or infinite Ω) especially power source trace, PCB via might be bro-
ken. You'd better replace MAIN board.
2-9-3. Service hint (Any picture / Remark)
ONE POINT REPAIR GUIDE
IC504
< MAIN board bottom view >
2-37
IC501
IC502
IC503