Flash, burning smell, computer dead: diagnosis?

[tiny-tim]

when i pressed the power button on my imac g3 desktop computer, there was a bright flash from inside the computer (it has a transparent blue top), and a burning smell such as when a fuse blows

i tried using a different power lead a few hours later, the same thing happened again

everything on it (except my emails) is backed up on another computer, but i'd like to revive it if i can

assuming that I've fried something (i haven't yet taken the lid off to look inside), is it likely to be an important part of the electronics, or is it more likely to be an easily replaceable component such as you'd find in an electric heater?

(further symptoms: for the last two weeks, the computer sometimes started-up ok, but sometimes did nothing at all on pressing the power button, and sometimes made the start-up noise but didn't do anything else: in either case, it then started up ok if i disconnected from the mains (i usually leave it connected even when swithced off) and then reconnected before pressing the power button again: does that have something do to with a capacitor? )

help! ​

 

[nsaspook]

The magic smoke escaped from the power supply.

http://www.dvwarehouse.com/iMac-Power-Supply-c-247_585.html?gclid=CMnRsMTb4a0CFQ41hwodmz3sTQ

 

[I like Serena]

If it were me, I'd open the lid and check a couple of things.

It sounds like it may be your power supply that might be fried.
So open the lid, disconnect the power supply from the main board, switch the power on, and check with a voltage meter whether you have power (6 V, 12 V, 15 V, whatever...).

This will tell you if it's either a fuse, the power supply itself, or the switch.
It's not unusual for the isolation in the coils in the power supply to have lost some of its capacity to isolate, which may explain your previous problems.
If that is the problem, you can fix it by replacing the power supply.