Have you repinned all the connectors yet? Start there, that’s the best place to start with any sys1. I’ve owned a ton of them.
I’d you can afford it I would replace at a minimum the cpu board with a Pascal, those are the best. Ni-Wumpf second. Again I’ve owned them all. All in one from Pascal if you never want to worry about another board issue for the rest of your own life. However the stock power supply and driver boards are pretty robust overall.