How can I stopthe channels changing on a Samsung SP46L5H Rear projection TV?

I have a Samsung 46" SP46L5H Rear Projection TV and the TV channels cycle upwards after it has got warm (about 20 mins). (It has nothing to do with the remote, and I have replaced the external switch assembly, as well as disconnected it.) It also switches back on after being put into standby. When cold, it's OK. If I run the TV through a DVD player, it stays on the same channel of course, but still indicates a channel change - most annoying. I have been told it is a capacitor on the main board gone leaky, but was unable to find which one, or even to be able to order the main board. At the very least I would like to disable the indication of channel change on the screen.