This is probably a stupid tip, but I managed to do this.
I bought a 400W powersupply as I was having problems with my AmigaPPC too. I made a mistake though by cutting the red 5V wire from the HD powerconnector. I did this because I wouldn't ruin the motherboard powerconnector in case it didn't work. Quess what, this 5V wire was probably never ment to supply huge currents as my Amiga didn't work. After I used the 5V wire from the motherboard connector my amiga worked just fine.
Perhaps there is a difference between the 5V for the HD and the 5V for the motherboard?
