I have a G3 500mhz Indigo iMac that had PAV problems.
I've made a new power connector to plug it into an ATX power supply and a new video cable but the video is dark, greenish/orangish and blurred.
I've tried a couple settings for the video but I get bad or worse.
Plugging into the onboard connector is no better.
I converted a 400mhz iMac here http://www.applefritter.com/node/10574