Replace power supply in G4?

It seems very unlikely that you have two of these Macs with dead power supplies, unless you bought them that way, and have evidence of sparks, smoke, or burned stuff.

Many Macs will misbehave and may not start at all if their PRAM Backup battery is low. For debugging, remove the PRAM battery if it is under 3.2 Volts and reset the PRAM/PMU using the tiny button nearest the battery. Hold for about a quarter minute, then wait at least five seconds before attempting to restart.

Those power supplies also have an internal fuse on the AC input, but the supplies must be opened to access it. It should only blow when the supplies have had way too much current drawn, such as from a short-circuit on one of the outputs.

Power supplies are routinely harvested from otherwise-dead Macs and resold on eBay for cheap.

The AGP has a 20 pin power supply, but requires mod of the ATX supply. See:

Power Macintosh G3 (Blue and White) and Power Mac G4: Power Supply Voltage Test
http://docs.info.apple.com/article.html?artnum=58561

G4 (AGP/Sawtooth) to ATX case Conversion
http://www.xlr8yourmac.com/systems/ATXG4_AGP_conversion/G4_AGP_to_ATX_casepg2.htm

Don't know if these are available, but check this out.
Power Supply Adapters
http://groups.google.com/group/lemswap/browse_frm/thread/1b2c5f07358e809c/a96b79 e1d5048047#a96b79e1d5048047

I believe that the Quicksilver has the 22 pin supply like the G4 Gigabit Ethernet. See http://docs.info.apple.com/article.html?artnum=95064

 Cheers, Tom 😉

I'm also looking for a new power supply unit for a Mac G4.

My dad's G4 has a 237 W box, and I'm looking for something with a little more kick. I was referred to http://atxg4.com by the same folks that I bought processors and hard disks from, for three computers.

This site sells prefabricated adapters for various ATX power supplies.

I also went by the local computer shop and asked about PSUs there and was told that Apple uses proprietary power boxes, as does Dell, so finding one that will work and give a fair amount of juice will be hard.

On the other hand, if you're looking for a part out of a mac to put into another, then ebay would be a good place to look.

Message was edited by: Cnz

This article may add a little insight. Read Carefully the notes at the top regarding the 28 Volt supply -- especially if you intend to use an ADC display!

http://www.xlr8yourmac.com/systems/ATXG4_AGP_conversion/G4_AGP_to_ATXcase.htm

Well, thing is that my dad's G4 AGP, which I'm trying to find a PSU for, isn't using an Apple Display.

What I really would like to do is find a PSU that will physically fit, as well as work correctly with it with out frying it. What's more, can I pick just about any 20 pin PSU, plug in the adapter for it, and let her rip, or is there anywhere I need to go in particular for a G4 AGP PSU that puts out more than 300 W?

Page 2 of the article above shows exactly what wires to modify to turn an off-the-shelf ATX supply into a supply for any G4 up to Gigabit Ethernet G4. Includes wiring diagrams and photographs:

http://www.xlr8yourmac.com/systems/ATXG4_AGP_conversion/G4_AGP_to_ATX_casepg2.htm#next