LG BH4120SN Service Manual page 40

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.
2-3. IC155 (NO 1.2 V)
2-3-1. Solution
Replace IC155 on MAIN board.
2-3-2. How to troubleshoot (Countermeasure)
1) Please check 1.2 V of C1A4 on MAIN board.
2) If 1.2 V voltage doesn't come out, check IC155 pin2 (VCC 14 VA).
3) If VIN (pin2) of IC155 is not 14 VA.
First, check CN150 and if there's no defective component, please check SMPS board.
4) After fixing it, if the set is still not booting :
Check L1E4 and finally check IC155 or replace.
5) After fixing it, if the set is still not booting :
- Refer to the next page for checking another power source. (3.3 V, 1.5 V)
- Check Crystal X501 refer to item 2-5.
- Check NAND Flash IC (IC504) refer to item 2-6.
- Check DDR IC (IC502, IC503) refer to item 2-7.
- Check MT8560 IC (IC501) refer to item 2-8.
2-3-3. Service hint (Any picture / Remark)
ONE POINT REPAIR GUIDE
C1A4 C1A4 C1A4
IC155
< MAIN board top view >
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