Is my LG fixable?

I have a 59" LG TV (60UJ6300) that one day just stopped coming on. Actually, it started with the sound going in and out, and then nothing. The red light on the power button comes on and reacts to the remote, but the screen stays dark, with no sound dark. If a light is shone directly onto the screen when the set is "on", one can faintly detect the LG logo slowly flashing on and off. I replacced the power board with one from a broken-screen TV of the same model, and no change. Then I replaced the main board with the same model. Still no change. I've disconnected and reconnected all the electrical connections visible with the back of the TV, using electrical contact cleaner as I reassembled them. Any hope for this TV?