I have the same model, e550-b2, 55" version. Exact same problem - has audio, but no video. I fixed mine by following this YouTube video:
https://youtu.be/NKdSrAH8_hs
Turns out I have the exact same root problem: the connector on the power supply board that's connecting to the driver board became loose, because the soldered iron broke off. I followed the video, removing the back board, took out the power supply board, re-solder the iron, and TV came back alive!
If this is also your problem, it's an easy fix. Took me 30 minutes and I'm no handyman at all.