Samsung UE55RU8000 power cycling (turning on and off)

I've owned this tv for 3 years when all of a sudden it started power cycling - with no apparent cause. It's not in warranty.

I know this appears to be a fairly common issue, but would appreciate some guidance as I have no idea what i'm doing.

I have taken the back off and when either of the two ribbons connected to the main board are disconnected, no image other than the back light appears on the screen, but the sounds runs. This happens with both ribbons and when they are both in place, the power cycling starts again.

Is there any recommendations on what I could do?

Incredibly frustrating and not in a financial position to buy a new tv.

One thing to add - sometime it will work for 30 mins/1 hour out of the blue and then revert back to not working.

Thanks.