I had similar symptoms on a firepower a few years back. My problem was the 5v supply. My voltmeter told me it was good but when I put an o-scope on it the voltage wave looked like crap. Replaced the power supply and it fired up. Kind of an oddball problem but might be worth looking at.
Tim

You could apply 5v on the bench to see if it will boot. If I recall you need to jumper the reset circuit. If you need more guidance maybe look at the manual for the system 3-6 test rig on www.smokingcircuit.com . It will give you the general bench power setup.