The poster says the TV goes off, therefore it still turns on. Usually if caps have gone the set will not turn on. IMHO the symptoms are of a surge diode gone out out of spec or a dry joint has developed. Again in my experience these are both much more likely to happen on the power board. (Having said this I have just finished one and it was the Video Board!!)
Finding the P Board is easy, just follow the power lead to the PCB and that'll be it. Plenty available on eBay for this model for about $50
Question - when the set goes off does it completely turn off or does some section eg sound still function??