You can always turn the button on the PSU by 90º to see if it was in the "always on" position. This was done as a failsafe on these machines in case they were used as servers and power was interrupted.
Of course, it could just be a wonky PSU or even something on the board. I have a IIci with the exact same issue, although the power-up isn't immediate. The board was re-capped and it's been problematic since, which I think is just the result of cursory work.
A few of us have come across the same problem recently - LCD stays on black once both logic board and LCD controller have been recapped, and it appears to be an unknown fault on the PB100 logic board itself. You can interchange the "black" LCD to another PB100 board and it works.
What that fault is I'm stumped, but more of us would like to know!
Now there's a name I haven't heard in a long time... didn't they make everything from PhoneNet adapters and Bernoulli drives to actual, full, Motorola-sub-licensed clone systems?
I guess the real test would be if you can clear PRAM with it my PowerComputing-branded ADB keyboard can't... among other things.