Powermac G5 (Dual Core 2.3) PSU repair?

[TheCorruptedBit]

Hello 68kMLA!

I recently acquired a G5 Dual Core 2.3, and it seems like the power supply in it is dead. It clicks twice when plugged in, and the "trickle power" LED indicator on the logic board only briefly lights up before going dark.

Somehow, I managed to get the Power Supply out of the mac, and thought that I might be able to repair it, or replace it with an ATX power supply - however, the last generation of PMG5s seem to use a power supply that's different from other G5s, as the connectors are completely different (and the PSU has bus bars on the top), so most online resources (like the Damn Technology mod, and every single pinout chart online) seem to be tailored to a different model of PSU. Picture attached:

Opening it up, I spotted what looks like a scorch mark on the other side. Not good! Most of the fuses read good though, and the PSU shocked me as I tried to turn the PCB over, so it seems like power is flowing through it - just not to the computer.

Does anyone here have experience with repairing these later PSUs, or replacing them with an ATX power supply? Replacement PSUs of this model are about $45 on eBay, but I don't want to spend that much only to find out that there's a simpler/cheaper/more reliable solution out there.
Thanks!

 

[QuadG5MacDan1138]

What’s on the other side of that discolored area?

 

[Builder68]

In my experience, a common fault in PowerMac G5 PSUs are the small, 4.7uF electrolytic capacitors soldered vertically onto a daughterboard attached to the mainboard. These capacitors likely play a role in monitoring the DC voltage rail for stability and preventing shorts. Replacing these capacitors can be a repair option, but it requires soldering expertise and carries the risk of damaging other components if not done carefully.

 

[Builder68]

Just replace any 3.3 / 4.7 uf electrolytic capacitor you found, even if the capacitance measurements reads ok

 

[Builder68]

PowerMac G5 psu not turning on - Badcaps

Technical discussion for power supplies. This covers PC supplies, and any other related power supply issue. When starting a new thread, please put the make AND model of your device in the thread title. Also be VERY descriptive of your issue, that way you'll get the best answer possible!

www.badcaps.net

 

[TheCorruptedBit]

I ended up recycling the old PSU and buying one of those replacements I was dreading... I thought about repair, or maybe replacing it with a modern PSU, but I couldn't find a pinout for the G5 PSU, and the PSU kept shocking me as I tried to handle the board. So frustrating to know that the answer all along was bad caps!