Wow! Got so many replies so quickly. Thank you all so much.
Yes, I was already getting ready to put my wife's HD into an enclosure and boot it from my iMac.
Taking the iMac to the shop is my last resort. I'm trying to determine if it's something I can fix and pay for the parts, only. If I can positively determine it's the power supply it would be a waste to pay for labor, as I can just replace it myself. I just want to make sure it is in fact the power supply, before buying a replacement.
Also, if there was a way to positively determine that it was a bad cap I could obviously change the cap. But I have a feeling it is not a bad cap.
If its completely dead it may be something quite simple...
That was exactly my thinking.
...before you start doing things, since you have another computer, you should try to find the Apple repair docs on that particular model, If you are certain you both have the same machine, look in your "about this Macintosh" The model name should be there...
I do have the exact same machine but can't find Apple repair docs in "about this Mac". I also looked a bit online (even before I posted here) but not found the resource, as of yet. I'll look some more.
In the "about this Mac" it says it is an iMac12,2 but when I look online I find different model names, such as "iMac 27" Intel EMC 2639", and so on. I just need to look some more.
Try the repair manuals resources listed here in the wiki...
I didn't know there was a wiki here... I'll look.
I would NOT at this stage put your other power supply in this machine...
That's why I asked. For future reference, is is possible there is something else wrong, which killed the power supply, and I risk killing another power supply with such test?
Yeah, completely dead and silence, most likely is the primary greenchip, mosfet and fuse...
I was also thinking that if it was just faulty caps I'd still be seeing/hearing some activity.
After I reassembled the Mac I also though it could be a fuse, but I don't remember seeing a fuse on that board. I'll take it apart again and look for one.
Again, I cannot thank you enough, all of you, for replying so quickly.
There is still one question I would like to know the answer to (also just for general knowledge). Can one just connect any switching power supply to the mains voltage if there are no loads on the outputs?
Thanks...