Unit fails to power up
My unit fails to stay powered up. Comes on for a few seconds, then powers down. Then it doesn’t power up. This sequence occurs repeatedly.
Plugs and power leads have been changed.
It does sound like your power supply is failing iMac G5/Intel Power Supply and here’s the guide you’ll need to follow iMac Intel 20" EMC 2105 and 2118 Power Supply Replacement
This series PSU’s might have defective electrolytic capacitors Capacitor Plague.