The results are in:

I went upstairs this fine frigid Christmas Day and I pressed the power buttons JUST ONCE on each iMac and what do you know, they fired right up.

The room is COLD and probably closer to 55F.

It appears that they made a liar out of me.

I guess those old PSU CAPs still have some life left in them after all.

I only shut the systems down yesterday afternoon. Could the PSU CAPs still have been holding enough residual charge?

Maybe I will power down and wait some longer period before trying again. I'm thinking maybe a week.

Any thoughts out there on what's long enough to fully discharge the CAPs?

Brian