I've been trying to repair my G4 MDD power supply for awhile now and not sure what exactly to replace on it. I've replaced all the caps except for the 3 big 450v ones. I know that the mosfets also should probably be replaced (presumably the ones on the heat sinks). Not sure if anything else would need to be replaced. Id much rather restore this power supply rather than ATX mod one so I can have ADC support. Any help would be appreciated.
PowerMac G4 MDD Power Supply
- Thread starter Duke09
- Start date
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- Tags
- mdd pmg4 powermac g4
It can be a lot of things. You need to narrow down where the failure is whether it’s the primary or secondary and which rail(s). I recently repaired a PSU which turned out to have a bad optoisolator. It seemed to test fine out of circuit but replacing it did the trick anyway. There are a lot of videos about SMPS repair on YouTube and I recently came across this PDF which was helpful. Good luck! https://electrohosh.com/wp-content/uploads/2018/10/smpsrepairebook.pdf
What a great resource! I have a PowerMac G4 Quicksilver with a dead PSU that I've been meaning to repair for years. I read through much of this guide, and I think that I have a better understanding of what to do now. I'll have to finish reading this and see if I can find the fault in my PSU now. I still need to read the safety section before trying anything.
My PSU has a problem where it blinks on and off but it never starts up all the way. @Duke09 what are the symptoms of your broken Power Supply?
Before the power LED would turn on for a second and the fans and then turn off. After the recap it does nothing now. I checked some of the mosfets and all the pins are shorted so that’s probably why.What a great resource! I have a PowerMac G4 Quicksilver with a dead PSU that I've been meaning to repair for years. I read through much of this guide, and I think that I have a better understanding of what to do now. I'll have to finish reading this and see if I can find the fault in my PSU now. I still need to read the safety section before trying anything.
My PSU has a problem where it blinks on and off but it never starts up all the way. @Duke09 what are the symptoms of your broken Power Supply?
Sorry for digging up an old thread, but for future users I wanted to point out that on eBay exist power supply converter cables for various G4s and MDD included.
I repaired the API1PC36 REV:A PSU on my MDD a couple of years ago. There's a number of useful threads on badcaps.net and the best for me was:
In my case, the culprit was one of the smaller electrolytics on the hot side. But I first had to replace all the secondary filter caps termed the "shotgun 12 caps" though all of these measured fine after replacement.
PowerMac G4 MDD ACBel Power Supply issues (API1PC36 400W) - 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
Powermac MDD ATX converter cable
I think the cable is a pretty elegant solution to a problematic PSU in a MDD but the thing about the ATX mod is that you lose ADC power, so if you use a ADC cinema display, you'll need to rethink that monitor or grab something like a a1006.
Love my MDD and very bummed the power supply suddenly died with no warning. Thanks!
Those adapter cables are pricey. If you are so inclined & have the time, below is a link to an DIY adapter guide for the MDD.