Power Supply Repair Extension program for some PowerMac and 20-inch iMac G5 models
"If your Power Mac G5 fails to start up after the power button has been pressed and your computer's serial number is within the noted ranges, your computer may be eligible for repair, free of charge. There are no known safety issues caused by this component failure."

For more info and how to identify if your PowerMac qualifies, please see:
http://www.apple.com/au/support/powermac/powersupply/repairextension/

"If your 20-inch iMac G5 fails to start up after the power button has been pressed or exhibits intermittent shutdown issues and your computer's EMC number is 2056, your computer may be eligible for repair, free of charge. There are no known safety issues caused by this component failure."

For more info and how to identify if your 20-inch iMac G5 qualifies, please see:
http://www.apple.com/au/support/imac/powersupply/repairextension/