PowerBook Duo 250

I got in a PowerBook Duo 250 w/Mini Dock, Floppy Drive and AC Adapter. The machine boots and stays on for a minute, then shuts off. I have attached a SCSI CD-rom drive and booted to the OS7.6 CD. It gets halfway through and shuts off. The DC in-board does not appear loose, the power supply tests good. It does the same thing with the battery in and out. I've hit the reset button, same result. Any ideas? The machine is near mint with a crystal clear screen and i'd like to get it running properly.