My LG TV has a flickring image, sound works

I found a dead LG 50LF6090, so I replaced it’s PSU, and it worked very well.

But after about two weeks, the image began to flicker every couple of minutes, it worsened, and now it always has the flickering.

I really don’t know what to do, I looked online and found a lot about T-CON board, but my TV doesn’t have one.

how can I diagnose/fix this?