When I try to power up my PowerMac, either with the power button on the front, or on the keyboard, I hear two clicks from the PSU, and that's it. No fans or HDDs spinning, no power LED, nada.

Tried CUDA button reset and logic board reset, tried removing the battery, tried removing and re-seating the personality card, RAM, ROM and Vreg.

I figured it might be the PSU, so I connected an ATX PSU with the -5V and P_OK pins removed. I changed the jumper J28 to PS/2 Supply, and tried to power up. Now the PSU fan spins up, and the HDD spins up, but still no power LED, chime, or any other signs of life.

So, am I looking at a dead motherboard here? There are no signs of physical damage. The board was stored for a while, but the battery was removed. Help!! 🙁