Feb 28, 2012

Standard ATX Power Supply in PowerMac G4 MDD

 My PowerMac G4 gets a heart transplant... That's just me... saving lives, day by day...

 The PowerMac G4 Mirror Door Drive was quite an abrupt departure from the computer towers of the day. As well, the power was something that challenged intel, often beating their CPU’s with only half the clock speeds. But what’s a PowerMac with a dead power supply? Well, for a few months, it was a nice decoration. I’ll show you how you can restore that floor decor into a respectable power house!

No give-sie back-sie!

 One day, I got an email from somebody that was asking for computer repair. I was the only person in the area that specialized in Macs, so the person was happy to stop by and let me take a look. I immediately concluded that the power supply was gone, which is an inherent flaw in the Mirror Door Drive.
 On a whim, I asked the owner if he’d consider trading it for a PC I had just picked up the same day. He said, “a working one for a non-working one? Might as well.” So we swapped the hard drives and he left satisfied with his new Pentium 4.
[It was intel’s Pentium 4 that the PowerMac used to stomp]

 Without thinking too much of it, I simply left the PowerMac sitting at the foot of my bed for three months.
 Finally, work was slim one week and I was getting restless. I looked over at the beautiful G4 and decided that it deserved to be humming along playing iTunes and Quake rather than collecting dust.

We can rebuild him. We have the technology.

 I realized that the molex connector on the motherboard was a standard 24-pin ATX! I also realized that a standard ATX power supply with 24 pins had all but one of the right leads! But was that one lead the crucial factor that would bury my plans? Considering you’re reading this post now, you can probably guess that no...no it wasn’t.
 That one pin is the 25v supply for the Apple Display Connector. If you don’t use an Apple Display with an ADC connector, then this is a non-issue and we can continue!

 Because this was simply experimental, I wanted to keep a tight budget. I spent $45 on a standard 350w ATX power supply at Best Buy. The first MDD G4 used a 400w power supply and the later models used 360w. I am not certain if the 400w power supply was simply a redundancy or if it’s necessary, but I know that using two hard drives, one DVD drive, and an ATI Radeon 9000 Pro graphics card, I never had an issue with the power draw.

 I didn’t want to ruin the power supply if the experiment was unsuccessful, so rather than snipping any wires, I simply pulled the pins from the Molex connector to rearrange them. This is the guide I used:
[Keep in mind that this is how the pins should look if viewing from the back of the connector, not the end with the pins.]

 After arranging the pins, I connected the PSU to the motherboard and tested it open. Bingo! I was exhilarated to see the power button light up and to hear the gong... Of course it didn’t boot because the drive still had a Windows installation on it, but that was taken care of with a Tiger install disc.

 It was running excellently with no hang ups, so I figured it was time to make it work while closed. After fumbling around enough, I was able to squeeze the beast into the PowerMac ever so.

I simply strung some hanging-wire through the holes in the top of the metal frame and suspended the PSU in such a way that the graphics card, which occupied the lowest [AGP] slot, would slip under it with a bit of wiggling.

 The downsides to this specific setup are that I can’t place any 64-bit or full-sized PCI cards into the slots and the power supply would just heat them with its exhaust.

 So there we have a perfectly functional (minus ADC port) PowerMac G4!

 Now that I’ve done all of the experimenting for you, we can feel more confident in using a standard ATX PSU. Ideally, you could use a Mini ITX power supply that would fit in the original power supply’s slot! This would  allow you to fit any PCI card into the slots!
 Finally, the most straight-forward process would be to simply cut the cable from the original MDD power supply and splice the wires to the new PSU, matching the voltages of course. Simply remove the brown 25v cable from the molex connector and the cable would fit and connect just as intended!

 I’d like to give this another try with a Mini ITX power supply some day.

Oh this would be simply beautiful...

Don't forget to comment below, follow at the top, and email me questions! No sign up required!

1 comment: