LG BH4120SN Service Manual page 44

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.
2-7. IC502, IC503 (DDR3 MEMORY)
2-7-1. Solution
Replace IC502, IC503 on MAIN board.
2-7-2. How to troubleshoot (Countermeasure)
1) Please check 0.75 V of DDR3_VREF (C545).
Please check 1.5 V of C523.
2) If it doesn't work even though IC150, IC155, IC151, IC101 are no problem,
IC502, IC503 (DDR memory) could have problem.
3) After changing it, if the set is still not booting :
- Check MT8560 IC (IC501) refer to item 2-8.
- Check MAIN board refer to item 2-9.
2-7-3. Service hint (Any picture / Remark)
IC501
IC504
IC503
< MAIN board bottom view >
ONE POINT REPAIR GUIDE
IC502
2-35
C523
C545
DDR3_VREF
< MAIN board top view >