So, I seem to have the common IIci issue of the machine spontaneously shutting down. Mine is configured, as follows:
2gb Quantum Grand Prix 7200rpm
Radius PrecisionColor Pro 24x
FWB JackHammer, currently connected to nothing
I had assumed that the problem was either the PRAM battery, or the PSU. So, when replacing the PRAM battery did nothing, I replaced the PSU with a known-good unit from a 7100, to make sure that I had sufficient VA. Neither seems to have done the trick.
In my case, it does take quite a while for the machine to decide to spontaneously power off. It's usually over an hour, which is about the time that I always think I've fixed the problem.
I don't see any obvious failed caps on the board, but I'm not an expert.