Apple emac booting problem

I recently installed a fresh copy of Tiger on my emac and after using it for a bit it turned off by itself and won't turn on unless I plug and un-plug the power cord a few times. Once it does turn on it always just goes to the open firmware screen and if I type "mac-boot" the emac hangs. I replaced the logic board battery and reset the PMU and still does the same thing. I also reset the nvram and did a "reset all" command, but no matter what I do it always brings me back to the open firmware screen and won't go past that. Any ideas on what I can do to fix this would be really appreciated.

Have you tried booting from the Install CD/DVD? Hold down C after the startup sound. Will that boot all the way to the installer? If so I have a feeling the shut down messed something up on the OS. Do an Archive and Install and that should fix it. Let us know what happens when you try booting from the Tiger DVD.

With an Archive and Install you will not lose any of your settings.

I've tried that already. I think the actual PMU unit on the logic board is gone. I have to press the power button about 10-20 times to get the unit to turn on and once on it automatically goes into the Open Firmware screen and says, to boot type "mac-boot' Command and when I do that it starts to boot and hangs an turns off the computer. I've been going crazy all day trying to make it work. Any other ideas? Thanks for the reply

The only issue like yours I have ever had (where I had to press the power button a million times) with an older Mac (iMac G3) was the PRAM battery was dead, but you have already replaced that. Will search around and see what I can find.

yea I replaced the battery and reset the PMU, but its strange because I had just installed tiger and was working perfectly. All of a sudden it just hangs and when I restarted it, it comes on with a long beep and went to the open firmware. The ram is fine because its the original memory module, so I replaced the battery because the voltage was low and same thing goes right back into the open firmware. I even tried booting the tiger cd from open firmware but it won't work. If you can find out anything I'd applicate it

I finally get it to turn on a bit quicker. If I press the power button 10-20 times it turns on and it still goes straight to the open firmware. I am unable to boot for the cd drive. When I do "mac-boot" in open firmware, it attempts to start, shows the apple symbol, the screen goes dim and crashes. I am able to hold "T" and go into target disk mode. Thats is about it