Shut downs? Is it the power supply or not?
I'm working with a 2010 iMac. Out of the blue, as of Monday, the machine has been shutting down. These are dead-stop shutdowns. No warning, no KP. The machine stops going as if somebody yanked the cord out. Sometimes it will let me start it up right away while other times it won't turn on again unless we wait 5, 10, 30 minutes.
I vigorously shook all cords and sockets etc.. No response there. So, my guess is that something is goofy with the power supply. But that's just a guess, of course.
How would I test that? I've never run across this before. I'm assuming AHT would only give vague if even useful information. Where should I turn now? I want to pin it down for certain before I order a part and go into the operating theater.