Looks like a panel failure to me. Of course you've cleaned the connectors between main and T-con and between T-con and panel. Another idea is to remove one flexi between the T-con and panel, switch on, and see if one half of the screen gives a good picture (or a clean white 1/2 screen with no input). Then refit that flexi and remove the other one. Repeat the process. If you get a clear screen on one 1/2 but not the other, the panel is definitely faulty. I'll upload the service manual to the forum. It includes a "panel test" with on board patterns.TH-L55ET60A.