I recently did some work on an iMac-G4@800 I picked up. When I was putting the drive caddy back in place, I hadn't pushed the power Molex connecter in firmly all the way (very tight fit). Opened it up and redid the connecters, and all is good. Those PATA/SATA adapters are finicky, make sure all the connections are good, and that there is no pressure on the connectors. Maybe some small cable ties and/or electrical tape to fix the connectors in place.