I have the same tv with the same problem. Not the power supply, not the inverter boards. I'll try a used main board and let you know. Did you get yours going yet? If so what was the problem?
It can't be done. The DVD remote will be single frequency for that device only and the LG remote for that LG Blu Ray (or series) only. Companies don't make cross-control between makers easy. The only exception is cable and satellite boxes to allow their remote to also control the television.
If you have lost a remote or it doesn't work, this is the answer
https://www.fixya.com/support/r29872378-universal_remotes_no_facsimile_remote
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