Might sound stupid, but i had a falcon doing the same sort of thing. It would turn on and play for 10-15 mins and then just shut off. I would then have trouble restarting properly. I triple checked all my solder joints and applied new paste, then done the xclamp fix but it was still doing the same thing. I ended up using a power supply of an old zenon (203w) and bang, worked like a charm. My kids have been playing it non stop for the last 2 months with no problem. I don't know if it will work for you, but it might be worth a shot.