Problem with TV Toshiba 50L7335DG

[preebi4]

Hello, I'am having trouble with TV Toshiba 50L7335DG. The tv turns on, backlights is starting but no picture. I think there is audio but not sure because cant test it.  There is only noise like working but no input signal. The question is how to understand where is the problem - main board, t-con board or lcd panel. The power supply board seems to be working fine because all voltages are correct.  Main board is 32L4300 rev 1.02a, t-con is v420hk1-cs5. I try to find schematics to check some control points but nothing came up ( maybe search wrong i dont know).
Thank You!