Power issue on dual 1ghz G4won't finish startup

My dual 1 ghz tanked yesterday. It had been turned off and when I turned it back on it was totally dead. My internet research steered me to resetting the PRAM which made it come back to gray apple startup screen>black screen. I then reset the pmu and got gray apple startup screen>white screen. Then I used my laptop to access the drives using firewire target mode, and reinstalled leopard. Same result. Finally I removed the battery, discharged remaining charges, let sit overnight, bought a new battery, and just for the fun of it reset the pmu and PRAM. Still starts up normally, but then defaults to now a blue screen. Removed ram and restarted: same result. I am in the process of reinstalling tiger on the second internal drive now. I was able to run disk utility from the install disk and all volumes are ok. any thoughts? thank you.
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Sounds like your logic board might be a problem . . .

How long have you waited for it to boot? For whatever reason my iMac was taking 15 - 20 minutes to boot until I reformatted it. Let it go for 30 minutes. Let me know.

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