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MP 3.1 PSU Repair

Roman78

Roman78

macrumors 6502
Original poster
May 7, 2018
380
131
Eifel - Germany
I wonder if someone here already repaired a failing PSU from a MacPro, regardless which version. At this moment i have 2 defective PSU's here from some MP 3.1. Both act like the same. The computer start short and turned off again.

Now there are some bright people on here who do more than just like replacing the defective part. As this is a kind of common problem of the MP PSU's maybe someone has or could make a guide of what parts to replace.
 
Power supply in my 3.1 went south two days ago. Would like to know what generally goes south in the Power Supply when this happens.

Fans spin for about 5 seconds and then it shuts off. Removed RAM trays, same behaviour. Pulled GPU, same result. Took out RAM trays and GPU. No chime, same behaviour. Suspect power supply above all else. After 10 years, I'm not shocked.
 
Capacitors definitely have a finite lifespan, and classic Mac Pro owners are walking toward that reality, or, have reached it unfortunately.
The thing I don't get, is that in all these years I've never once seen a service that refurbishes a cMP PSU. I've had a Samsung serviceman come to my home and replace 3 or 4 capacitors on my LCD TV. Took him 10 minutes.
So why not the same thing on our PSU's??
 
Likely we're a niche product group... I don't know how many cMP Apple have sold, but Samsung likely has sold a few million more LCD's. I agree with you though, that this would be great. Alas, computers have a finite lifespan vs a panel that strictly displays an image, although with the advances in that department, who knows...
 
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Well there are some services available from some companies to repair a MP PSU. But there is no DIY like for fixing the MBP 2010 or 2011. Normally i only repair PSU from older computers like Amiga, Commodore or BBC. This is a new level for me. There is a lot more of stuff in those PSU compared to one of C64 :D I could measure the Caps one by one, but there are a lot and mostly there are only some failing.

Oh i repaired some iMac G5 PSU some time ago, also leaking caps. But those i could easily identify because they were leaking. Those in the MP PSU are all looking fine. I read somewhere that it is a problem whit cold solder spots, but also all the soldering looks fine.
 
Suppose the easiest is to buy a replacement and move on. If it was easily repairable, I'd be all for fixing it. This is beyond my scope of expertise. After 10 years, it's not overly surprising they are failing. Particularly in the case of mine having been used for 3d rendering before I got my hands on it.
 
Well.. thats not the spirit... Actually I still own 4 of those MP 3.1 so spare parts enough. But it is about the satisfaction to get something to work again. I know we are living in a disposable society and i don't like to trow stuff away which could be fixed again.
 
Definitely agree with you here. I don't intend to throw the old PSU out at all. If it's fixable, I'm all for it. I'm going to hang on to it for now and see what can be done.

The only forum member I can think of off the top of my head that could repair them might be Dosdude or Lightbulbfun. Their skill sets seem otherworldly to me.... There are probably others, but there's been no feedback thus far.
 
You should absolutely check the 300+ Volts primary capacitors and discharge them with a light bulb (no Energy Savers, lol). Light Bulb with wires is always handy in a PSU repair shop. Also you have optical feedback.

Take good caution, discharging those high capacity with your body is at least painful...

Also live measurements should ONLY be thru a insulating transformer (big !)
 
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Appreciate you saving me from potential death here... Joking aside, appreciate your advice. The article was a good starting point and the whole subject worth researching. As time goes on, replacement parts for these towers will get more difficult to find.
 
There is a really big energy load in the primary caps in such a big PSU. I do this for living and even with a lot caution it happened a few times getting bitten by mr Osram. Feels like someone rips your arm off, if you catch the full load, no fun...
 
so would my power supply be suspected IF im running my mac pro 3.1 for like 2 days straight and suddenly it acts as if it goes to sleep and i loose all connectivity and it acts as if it goes to sleep? i posted today about my mac pro doing this, replaced all 32 gigs of memory and it works well for 2 days at a time, then it makes a clicking sound and then everything turns off, except my main power button is still lit up and both monitor lights flash slowly as if asleep...i have a usb expander plugged into the back to allow for more usb devices as well as a firewire 5 port hooked up back as well....all connected to a back up battery
 
Roman78 said:
I wonder if someone here already repaired a failing PSU from a MacPro, regardless which version. At this moment i have 2 defective PSU's here from some MP 3.1. Both act like the same. The computer start short and turned off again.

Now there are some bright people on here who do more than just like replacing the defective part. As this is a kind of common problem of the MP PSU's maybe someone has or could make a guide of what parts to replace.
Click to expand...

I would focus my checkup on three main components together with some essential tools that might be able to help you in the process.

#1 Transistor kind of components (Tyristor/Transistor/Fets/Mosfet and derivatives)
(Leistungselektronik hat erfahrungsgemäß den größten Verschleiß und obliegt der Alterung. Dreifuß-kandidaten mit und ohne Kühlkörper, messbar je nach Halbleiter Sorte, Gate Spannung usw..)

#2 Caps as mentioned below.

#3 AC/DC elements (Spannungswandler bzw. Gleichrichter von AC auf DC sowie andere ähnliche Konsorten wie Leistungs-Dioden usw.)

The use of a big magnification glass can be helpful at times. Sometimes the component level damage is visible.
(Lupenleuchte mit Vergrösserungsfunktionen :)
Other than that, more sophisticated equipment such as an Oscilloscope can be helpful as well as an FLR camera or a device with multiple temperature sensors (Fluke) can be helpful to detect hot spots. (on the other functioning PSU's as well as on the damaged PSU to compare heat signature) to have a comparison. Temperature sometimes can hint to failure or defective parts.

Good luck, Detective Spürnase!
 
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j2048b said:
so would my power supply be suspected IF im running my mac pro 3.1 for like 2 days straight and suddenly it acts as if it goes to sleep and i loose all connectivity and it acts as if it goes to sleep? i posted today about my mac pro doing this, replaced all 32 gigs of memory and it works well for 2 days at a time, then it makes a clicking sound and then everything turns off, except my main power button is still lit up and both monitor lights flash slowly as if asleep...i have a usb expander plugged into the back to allow for more usb devices as well as a firewire 5 port hooked up back as well....all connected to a back up battery
Click to expand...

Try to reduce load as far as possible for a test run. Pull all spinners but the system ssd, pull most of the ram, reduce the machine to a bare minimum.

Like a car with a dead battery.

If it survives it might be the PSU
 
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Macschrauber said:
Try to reduce load as far as possible for a test run. Pull all spinners but the system ssd, pull most of the ram, reduce the machine to a bare minimum.

Like a car with a dead battery.

If it survives it might be the PSU
Click to expand...
Thanks im about to run a hardware test and a few others then ill report back
 
So i threw in a different video card fired it up

Fan spins then stops screens go to sleep state slow flashig lights and power light above button stays bright but nothing really works


More than likely its the darn power supply it just wont fire up now, might be a video card as well? Who knows, might be time to get rid of this monstrosity and stay w my mac mini and macbook pro
 
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howiest said:
Capacitors definitely have a finite lifespan, and classic Mac Pro owners are walking toward that reality, or, have reached it unfortunately.
Click to expand...
+100 this one....

The "use before" date for cMP systems was quite some time ago. Betting your business (or your paycheck) on the reliability of six to twelve year old components is a fool's errand - especially when the best place to find replacement components is to get used components that haven't failed yet on eBay.

And power supplies are the worst items. If you've ever looked at servers, you'll have seen that all but the lowest end servers have hot swap dual power supplies for N+1 redundancy. Many of the HPE servers that I buy have four power supplies, for N+2 redundancy. Scary when a server has 6000 watts of power supplies (four 1500 watt supplies on a 240 volt power strip) - but absolutely necessary when it needs at least 3000 watts to run.
 
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@Macschrauber thank for the tips. Never usesed a UV-Light to see electrolyte, ill try this when i find mine. And the Lamp to unload the Hi-Voltage caps is also a good idea. Now i use a Multimeter and wait, but a lamp would go faster.

I did not found any blown Caps, that would be obvious. But I found some dodgy soldering spots at the Coil on the Low Voltage side.

@AlexMaximus what do you mean with Gate Spannung? Should i Remove the Transistors from the circuit board for the measuring. I have a little respect for measuring under load. Last time i killed the copper in a Atari PSU while measuring the frequency.

I own a Oszi and Thermal Camera. And a Microscope Camera for the small parts.
 
Macschrauber said:
Try to reduce load as far as possible for a test run. Pull all spinners but the system ssd, pull most of the ram, reduce the machine to a bare minimum.

Like a car with a dead battery.

If it survives it might be the PSU
Click to expand...
Ota and otb start flashing red which from my understanding is an over temp, but is it an over temp from the memory rizers or the power supply? I took a video and as it over temps the 4 dimm lights flash red and then the computer stops working, yet the front power button is still lit. Not flashing but lit bright
 
Do these temps look too high? Also my memory is like 800 mghz not sure but maybe too high for a 3.1? Thought 667 was the highest it was supposed to take mghz wise?
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Macschrauber said:
800 mhz is ok for the ram

The rpm of the fans are too low for those temp sensors imo.

Try smc reset and 4x pram reset in a row
Click to expand...

Ive done so many resets on this today its killen me smalls hahah

Got a fan app i am using to try and increase fan speeds, not sure why fan speeds are so dang low?
 
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