My 2002 iMac G4 went down during a power out. won't restart. tried PMU button. still won't start. fan tries for 2 sec, but nothing

Question

my 2002 iMac G4 went down during a power out. won't restart. tried PMU button. still won't start. fan tries for 2 sec, but nothing

Answer 1

Sometimes, a replacement 1/2AA 3.6v Lithium PRAM battery is needed
to get these back into running form again, because these are one-way
and without a good battery, settings are lost or easily corrupted. And this
can contribute to a failure on startup. But that is a troubleshooting measure.
There could be another issue, although these batteries are only good for a
few years at best. A power outage can revoke any remainder of life out of it.
The take-apart is tedious and detail oriented; to include new thermal paste
and some special tools, good instructions, and some skills also help. An
ifixit.com repair guide may help; as would an original Apple Service guide.
Not sure if other good online guides or youtube video are available.
If the power supply is bad, the test ports near the PMU button are where
to check; with multi-meter. Also power supplies may develop issues with
bad capacitors. They have been said to be repairable.
Here's an older site with a take-apart from some time ago.
http://www.xlr8yourmac.com/systems/imac_g4/imacg4_takeapart.html
This also would be a good time to consider, if battery is all that's failed, to
upgrade the internal RAM chip, or upgrade the hard disk drive, etc.
Good luck & happy computing!
edited