LG LAB550H Service Manual page 41

If your BD sound plate set doesn't work by no power problem, repair the set according to the following
guide.
1-2. 24 V main power
1-2-1. Solution
Replace Q901, D991 on SMPS board.
1-2-2. How to troubleshoot (Countermeasure)
1) Check Q901 and replace it with a new one.
2) Check D991 and replace it with a new one.
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1-2-3. Service hint (Any picture / Remark)
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ONE POINT REPAIR GUIDE
Q901 Q901
< SMPS board top view >
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2-28
D991 D991