Hi. I have a G4 Digital Audio that's had gradual mods over time, including a 1.5 GHz processor, a TB of storage with the two internals and two externals, a 128 MB video card running dual 22" flat panels, a super drive and a pair of USB2 PCI cards. I added a couple of lighted fans inside of the case and another fan that cools the video card installed in one of the PCI slots.

So I have a lot of stuff plugged into the thing, including my Wacom tablet, a webcam, printer, iPod, etc. A while ago I noticed the case was getting hot and discovered that the power supply fan wasn't spinning. I can coax it to spin when I start up by helping the blades get going with a plastic toothpick, but that is a sucky workaround. I'd like to put a new supply in, perhaps something with more power than the original which, I think, is a 338 watt box? So the question is, can I just pop in to the local Best Buy and pick up any off the shelf supply, or is it more likely that Apple used something funky that's going to make this difficult and expensive for me to do? If any of you have experience with this machine or can offer me any advice, it would be greatly appreciated. Thanks in advance!

if this PSU works just fine you can simply replace the fan in the current PSU. To be honest that might be less work depending on what tools or skills you have.

If you really want to swap the PSU then look here:
http://www.outofspec.com/frankenmac/wire.shtml

I would suggest just replacing the fan in your current PSU though. It will be 80mm, 12v. Just get one with the same or higher CFM rating and you should be good to go.

Oh. Sweet! I never even thought about replacing the fan itself. Now I need to see if anyone sells those locally or if I have to hunt one down off the web. Thanks!!!

It is just a plain 80mm fan. you can get one at any PC shop. Just make sure it has the same or higher CFM as the one it is replacing.

I would go with a higher CFM rated fan to make things better in the long run.

Thanks guys! Works great and cost me a LOT less than a new power supply.

Glad to know that we helped.
btw, got any pictures from the results of (possibly?) your first venture into a PSU?