LG BH5140S Service Manual page 45

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.
2-2. IC155 (NO 3.3 V)
2-2-1. Solution
Replace IC155 on MAIN board.
2-2-2. How to troubleshoot (Countermeasure)
1) Please check 3.3 V of L158 on MAIN board.
2) If 3.3 V voltage doesn't come out, check IC155 pin3 (VCC_3.7VA).
When you figure out those power if there is no 3.7 VA, please check 3.7 VA from SMPS board.
For the solution please back to the solution 1.
3) If 3.7 VA input is normal, first of all check DCDC3.3_CTRL is high (IC101 pin58).
If DCDC3.3_CTRL is high, check R129, R181 and if there's no defective component then replace IC155.
4) If DCDC3.3_CTRL isn't high, you may need to replace IC101.
5) After changing it, if the set is still not booting :
- Refer to the next page for checking another power source. (1.2 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.
2-2-3. Service hint (Any picture / Remark)
IC155
ONE POINT REPAIR GUIDE
L158
< Main board bottom view >
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