LG LAB550H Service Manual page 43

When you turn on your set, it will blank / no message or Welcome on front panel, and it will not boot-up.
2-2. IC153, IC155 (NO 1.2 V & 1.5 V)
2-2-1. Solution
Replace IC153, IC155 on MAIN board.
2-2-2. How to troubleshoot (Countermeasure)
1) Please check 1.2 V of IC153 on MAIN board.
2) If 1.2 V voltage doesn't come out,
- Check IC153 pin3 (12 VA).
If there is no 12 V, please check 12 VA from IC154.
If 1.5 V voltage doesn't come out,
- Check IC155 pin3 (VCC 3.3V).
If there is no 3.3 V, please check 3.3 V from IC157.
3) If VCC input IC153 there are 12 VA,
First of all check the pin5 is high and if it's high
if there's no defective component please replace IC153.
If VCC input IC155 there are 3.3 V,
if there's no defective component please replace IC155.
4) After changing it, if the set is still not booting :
- Check 1.2 V, 1.5 V, 3.3 V is normal. (please refer to other sections of this guide)
- Check Crystal X501 refer to item 2-3.
- Check NAND Flash IC (IC502) refer to item 2-4.
- Check DDR IC (IC503) refer to item 2-5.
- Check MT8553 IC (IC501) refer to item 2-6.
2-2-3. Service hint (Any picture / Remark)
< MAIN board top view >
ONE POINT REPAIR GUIDE
IC153 IC153
2-30
IC155 IC155
< MAIN board bottom view >