You might want to make sure that there isn't a shutdown script in your startup folder (a popular joke around some offices). If you have the original CDROM that came with the iMac, try booting from it. If it lets you boot and run, then go check out the startup folder on your hard drive. Otherwise, if it still shuts down then you have a hardware issue. Also, try starting it up with the keyboard disconnected--a faulty powerswitch on the keyboard might create such a problem as well.

BTW, if you don't have the original CDROM (or any other that you can boot the iMac from) I believe that there is also a way to do a minimal power-up by holding down certain keys during powerup but I can't remember the sequence.

- Jeff


Andy Cuffe wrote:

I'm working on an orange slot loading imac that powers on normally with
the turn on chime, but shuts down about 5 seconds later. The power
light stays on (green), but the monitor and hard drive shut down. The
5v and 3.3v supplies to the logic board drop noticeably when the monitor
shuts down, but this may be due to the sudden loss of most of the load
on the power supply (the B+ to the monitor remains constant). Has
anyone seen anything like this before? I suspect a monitor/SMPS
problem, not a logic board problem. It has HV and vertical deflection
before shut down. Apple's service manual is useless.
--
Andy Cuffe