The power is perfect on 5 and 12 volts, and the ground is good. The harddisk powers up fine and the floppy light comes on when I pop a disk in, also the video recieves a blank signal.
What color/colors do you get on the screen ? These colors can tell you if there is a problem. I would first check all the voltages at the motherboard connector. There are files on Aminet that tell you what the bootup colors mean, and also what the voltages should be on the motherboard connector.
Ed King