You have bad capacitors. I had the same problem on my IIci and swapped PSUs twice, neither of which were able to solve the problem (both were known good PSUs). Some of the folks on here said it was likely capacitor-related. My IIci's board is actually out being re-capped right now thanks to one of our forum members, which evidently will solve the problem.

You should be fortunate your IIci lasted an hour. Mine was lucky to go 30 seconds before I sent the board off.