This is a Hitachi model 55R7 4K UHD Roku smart TV and is about 5 years old. It was working just fine until a week or so before the problem. It started with one side of the screen losing definition and 'ghosting' when the picture changes. This was intermittent, and I thought was solved after I re-seated all internal cables, however it came back and ultimately resulted in a total failure somewhere. Now, when the TV is turned on, I just get a black screen with a large blue splotch that fills the entire screen within a few seconds (see attached images). The TV will turn itself off after about 15 seconds. All symptoms made me suspect the T-Con board, which I replaced, but this did not solve the issue. I'm hesitant to declare a bad LCD panel because the entire screen suddenly died, rather than only sections of it. Maybe the mainboard should be replaced? This is only $25 but perhaps someone can tell me before I order that it's not the problem. Only other thing I could think of would be the LVDS cable. (If I unplug the mainboard end of that cable, the screen goes black...plugging it back in replicates the slowly expanding blue splotch each time.)

If it turns itself off after 15 secs, I would suspect something in the PS.
Check for puffed caps, poor solder connections, etc.

I have uploaded a video to YouTube to hopefully help with this issue. See here:

https://youtu.be/Ar4M8ufI_Kk

If your screen has two ribbon cables connecting to the T-con board, try disconnecting them one at a time. If you get a "normal" left or right side picture with one cable not connected, chances are the disconnected half of the screen is causing the problem.

If your screen has two ribbon cables connecting to the T-con board, try disconnecting them one at a time. If you get a "normal" left or right side picture with one cable not connected, chances are the disconnected half of the screen is causing the problem.

I tried this after first getting the problem...as I recall, the disconnected side just went all white. I'd need to pull the set apart again to confirm this, though. I tried both sides with the same result.