PRAM reset button checked?
Just eliminating the simple stuff. Next, i would wash the board and try it. The caps need to be redone but if you can get some life out of it, you know it's not the power supply or other components. As MinerAl says, swapping in a known working motherboard would be much easier to eliminate other issues. You could also put an LC575 board in and you have a Mystic upgrade
