Turning the mac on with the power switch near all the ports just flashes and never turns the computer on. The 1 LED is on, and when I press the button with a screwdriver, the 2 LED flashes for a millisecond and shuts off. Is it the switches fault or the psu?
Earlier Mac models
If your Mac beeps during startup - Apple Support
The beep behavior of Macs typically is also followed by the sleep indicator on these Macs.
Look at the pattern fo the lights. It will usually indicate what's wrong. The manual might have information you need:
See if an authorized service technician will look at it. They should have the diagnostic codes in their documentation. They can also tell you if the capacitors were of bad quality or about to fail. These models were notorious for some having bad capacitors. At this age, it is not uncommon the recap capacitors by hobbiests that know how. Keep in mind this procedure should never be tried on any computer could potentially be under AppleCare or an Exchange/Repair program (which the G5 is not). Evidence of internal tampering of circuitry typically can make warranties void. Not that it matters on an 18 year old computer.
Those iMac G5s had so many capacitor issues with both the Logic Board and the Power Supply. One or both probably have leaking or bulging capacitors. Another possibility is a bad PRAM Battery. Remove the PRAM Battery to see if that allows it to power on.
There are no beeps, the mac does not start up.
iMac G5 power switch trip?
