Won't Start/Boot Black Screen, high spinning fans

Hi, I tried to read through every answer I could find on the 20" iMac g5 isight. -A1145.

Based on what i read I have reset PRAM, SMU, and replaced the power supply. Same problem.

When the power button is pushed the light on the front (lower right corner) lights. I hear a faint spinning, (HD, Optical Drive, fans????) The screen stays black. After a minute or so, the fans spin really fast, but nothing else but black screen. It stays stuck in that mode indefinitely. (at least it seems that way)

I could not find the led's some people have mentioned.

Any thoughts? Logic board maybe?

Thanks,