My XBR40800 did about the same thing. I ended up finding on the internet that it was a common problem and one IC needed to be replaced. I had a local repair come do it and he noted he had to do that same repair many times. The labor was 100.00 and I got the part online cheap.

Probably not the same thing since it's a different model but if you can't find it on the internet maybe calling a repair guy and asking might help.