It got really cold in the upstairs and I went to start the 2 iMacs albeit a bit earlier than I said I would. The older one will not start now, even with the blow dryer trick. The newer one took a few tries after the blow dryer treatment. There were a couple of false starts where the fan would start to spin but not quite and then finally a boot up.

My plan is to take out the power supply on the older iMac and to inspect and replace most if not all of the caps with higher temp low ESR CAPS. CAPS are cheap enough so I will double up on my buy and after the first one id fixed I will go and to the other iMac. There are variations even amongst the same models for these PSUs but I will chance it.

It may be a few weeks but I will report back on how well this turns out.

Brian