Hitachi 51F510 While watching TV there is periodically a very loud 'pop', then the screen goes black for 1/2 a second. The picture returns and everything is fine until the problem repeats itself, usually in about thirty minutes. The set is just out of warranty. The problem started yesterday

The loud "pop" sounds like high voltage arcing coming from one of the CRT's.....you may have to pull each CRT out and put silicon sealant on the anode connectors to prevent the arcing.(one of the CRT's may be arcing internally also and the only cure is to replace that CRT) If you let the arcing continue,it will short out the horizontal output transistor sooner or later.......