This is an IBM thing. When you get a replacment PSU from IBM the switch is set to the 220v setting, no where in the documation is it noted that that is the DEFAULT setting. And Yes it got me once.
The bad capactior is an industry wide problem. John
A few tid bits of food for thought!
A known problem with some IBM models consists of the capacitors near the processor overheating and swelling, sometimes leaking on the top. This is known to cause involuntary reboots and system shut down. I suppose it also posible that other system boards could be sporting some of these same capacitors so if you are having this type of problem you should check these capacitors.
On the not powering up syndrom one of the first things I check is the voltage switch in the power supply. If it gets inadvertantly switched to 220 volts the system will not power on. I had an IBM engineer miss this on one of their units when he and others were trying to trouble shoot one not powering up.
Just thought I'd throw this out to see if it helps.