LG LAB550H Service Manual page 46

When you turn on your set, it will display "WELCOME" on front panel, and it will not boot-up normally.
2-5. IC503 (DDR3 MEMORY)
2-5-1. Solution
Replace IC503 on MAIN board.
2-5-2. How to troubleshoot (Countermeasure)
1) Please check 0.75 V of DDR3_VREF (R567).
Please check 1.5 V of IC155.
2) If it doesn't work even though IC155 is no problem,
IC503 (DDR memory) could have problem.
3) After changing it, if the set is still not booting :
- Check MT8553 IC (IC501) refer to item 2-6.
2-5-3. Service hint (Any picture / Remark)
ONE POINT REPAIR GUIDE
< MAIN board top view >
2-33
IC503 IC503