Sony kp-57hw40 bright flashes

I have a sony rear projection kp-57hw40. It can run great for a week, then all of a sudden while changing stations will start seeing bright red flashes, along with lines, then unit powers off. Wait a few minutes and power back up, sometimes will do it 3 - 6 times in a row, but not necessarily always red. Predominantly red and green are the flashes of choice. Have adjusted the pot in the front for the green since, when watching a dark picture, could see some line traces across. Pot adjust removed them completely, but had no effect on the green flashes. Called service  and they immediately stated it was the red crt and of course, not made any more, also if I brought it in for $100.00 they would try and remove a short from the crt.v i think the problem is further upstream, and not the crt's. Looking for ideas. TV was mfg in 2002 and was one of the 90xxx serial numbers.

Any ideas on what to try next is apreciated... Johnnylj