imac g5 - is it brain dead?

My imac g5 (2gHz, 2G RAM, Ambient Light Sensor model, OSX 10.4.11) went black on me two days ago while surfing the internet. I could hear the fan running, but no picture. I held the power button down for 5 seconds to force it off. But when I tried to restart, nothing. I reset the SMU per this article iMac G5: How to Reset the SMU. After, I pressed the power button and the fan starts, but nothing else. After about a minute the fans kick into high gear and start going really fast. There are no chimes or normal start up sounds. The screen stays black.
Then I found this article iMac G5: Troubleshooting when your computer won't turn on . After going through these steps, the fan comes on and the power light pulses, but nothing else and again after about a minute the fans start going really fast. When I turn the computer off and then back on only the fans come on, no pulsing power light. I reset the SMU again, turn it on, and get the pulsing power light again
The diagnostic LEDS were: 1 lit up before I reset the SMU. 1 and 2 lit up after I reset the SMU. 3 and 4 never lit up.
I replaced the back up battery, no change in imac's condition.
I fear it's the logic board and not worth fixing, but how do I know? Could it be the hard drive? How would I test it?
Any help is greatly appreciated.

I think you've analyzed it correctly. From what you know now, it's not the hard drive.

Could well be the power supply from your description which may be worth the cost of repairs.

This link may help:-


http://jimwarholic.com/2008/11/apple-imac-g5-power-supply-issues-and.php

thanks

Thanks for the quick replies.
I'm glad you don't think it's the hard drive.

hb2448 - I had actually been to that site before I posted here. None of my caps looked bad, so I quit reading. I took the time to dig a little deeper and read that they don't have to look bad to be bad! I may just try this.

Thanks again.