PowerMac G5 DP that's been in storage for a couple of years. Just connected it up and it won't power on. A relay in the PSU clicks twice when the power cable is attached. Press the switch and the power LED stays on for a half a second, the relay clicks twice and the fans in front of the CPUs twitch and nothing happens. I've reseated the RAM and graphics card. No change. Removed all but the original RAM. No change. Any suggestions?