On start up - loud pop, burning smell, dead Mac. Help, please!

Question

This morning when my wife tried to fire up her heretofore reliable G5, there was what she described as first a popping sound followed by the smell of something burning. The smell went away quickly, but the computer now seems to be dead. My guess after looking through the forum is the power source. But having learned the hard way about making assumptions I'd like to run it by people (this forum) who know a lot more about my Mac than I do!
Does this sound like a power source issue, and if not what else can it be? Assuming the power source is the problem, how do I determine the correct replacement? I know the computer is a G5 2.0, but I'm not sure of production date, etc. that I might need to know to get the right replacement. Finally, where is the best place to get a replacement power source, hopefully without paying more than the value of the machine?
As always, thanks in advance for any help and advice you all can give me!

Answer 1

OK, before we go any farther, is the flat-liner G5 liquid cooled?
Actually, specific model information would probably help. Remove the big side panel and look at the tiny label at the bottom of the side of the computer. That will have, among other things, the serial number and some information as to the configuration of the computer when shipped. Using the serial number, you can get more specific information on the unit at
http://www.chipmunk.nl/klantenservice/applemodel.html
(It also appears that the first three digits in the serial number conform to the year and week of production. (310 means tenth week of 2003, for instance).
Usually, a popping sound followed by a burning smell means a capacitor. Those who have experienced such over the years recognize the smell of cooked electrolyte, as opposed to the smell of roasted magnet-wire varnish that accompanies a transformer failure.
While the power supply is the most-likely culprit, it could be a cap on the logic board or a PCI or video card. The good news is that such failures are usually easy to spot by visual inspection. That being said, not all capacitors are visible, like, for instance, everything in the power supply assembly.
While it would probably be relatively easy for an experienced person to diagnose, it probably is not something for the inexperienced to tackle.