MP 1,1-5,1 Is it time to give our cMP's PSU a recap?

donluca

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Jul 30, 2018
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I've read several reports of people having their PSUs dying, so I was wondering, since those Mac Pros are at least 10 years old, if it's finally time to get our hands dirty by opening the PSU, warming our soldering irons and give the thing some love with new shiny capacitors.

Recapping is a long, tiring process and I'm saying this as someone who has recapped lots of stuff, from hi-fi components with hundreds of caps, to old videogame consoles all the way down to (very) dangerous huge 29" arcade cabinets CRTs (never again, thank you very much).

Has anyone had any experience in recapping those?
 

MAFcz

macrumors newbie
Jun 26, 2018
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Czech Republic
I tried it once with PSU from MP 3.1 without success I just don't have enough knowledge repair it without schematics but if someone give me schematics I am able to repair it.

So is here anyone who has schematics of Mac Pro PSU?

PS: I couldn't find it on internet.
 

donluca

macrumors regular
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Jul 30, 2018
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Unfortunately I could not find any schematics or component list even on the service manual.

Although there are components (the usual suspects) which are clearly labeled when you see them.

On a faulty PSU I'd go for the electrolytics cap first, followed by the voltage regulators. If there's something else broken... well, you need to take out a good multimeter and start probing to see where current flows and when it stops or goes funky.
 

Mac Gus

macrumors regular
Dec 31, 2013
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My 2009 PSU died a couple years ago and I bought a used one on ebay for about $75 and replaced it and haven't had any issues since.
 

bsbeamer

macrumors 68020
Sep 19, 2012
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Seriously, if you don't know what you're doing with a PSU don't risk repairing it. There's a multitude of things that can go wrong working on it AND after installed if work was not done correctly. And if you think you're covered if you have renters or homeowners insurance and there's a major failure to your electrical system or even fire, just wait until the investigation and they discover it was repaired (by the owner themselves) instead of replaced...
 

donluca

macrumors regular
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Jul 30, 2018
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Just to make it clear: I'm not telling people to recap the PSUs themselves: if you don't have the knowledge to do this, then send it to an expert.

As for myself, I've been working with CRTs where there are 50.000V flowing through the circuit and can instantly kill you and I'm proficient in those kind of repairs (but so are other people).

The whole point of the thread is discussing whether it is time to do some preventive maintenance on our Mac Pro PSUs (or have it done by experts) or if they should be still good to go for 2-3-4-X years.
 

startergo

macrumors 65816
Sep 20, 2018
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Just to make it clear: I'm not telling people to recap the PSUs themselves: if you don't have the knowledge to do this, then send it to an expert.

As for myself, I've been working with CRTs where there are 50.000V flowing through the circuit and can instantly kill you and I'm proficient in those kind of repairs (but so are other people).

The whole point of the thread is discussing whether it is time to do some preventive maintenance on our Mac Pro PSUs (or have it done by experts) or if they should be still good to go for 2-3-4-X years.
I gotta say they are not reliable. I ‘ve Recently replaced my second PSU cause it started acting weird. Something i guess with switching (transistor maybe). When I press the start button it turns on and 3-5 seconds later off. On second hit it starts. Or could be leaky capacitors which need a recharge. But similar symptom I got with my original PSU but it worsened to a point where I had to keep the power button pressed to start. These are old PSU’s and they need a recap for sure. Nowadays though to find somebody to do the job professionally will probably cost more than 300 bucks.
 

donluca

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Nowadays though to find somebody to do the job professionally will probably cost more than 300 bucks.
Oh my god are you serious? I know I might sound sarcastic, but I think I might have found a nice way to make some extra income, LOL.

Really, I've done some recap jobs in the past, even of hi-end audio equipment but I can't remember making people paying more than €100 + components (generally 20€, more or less).

I'll definitely check my 4,1>5,1 PSU.
 

startergo

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Sep 20, 2018
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Oh my god are you serious? I know I might sound sarcastic, but I think I might have found a nice way to make some extra income, LOL.

Really, I've done some recap jobs in the past, even of hi-end audio equipment but I can't remember making people paying more than €100 + components (generally 20€, more or less).

I'll definitely check my 4,1>5,1 PSU.
I will definitely use a repair option for 100 bucks US wide.
 
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donluca

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Jul 30, 2018
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Well, I've never opened a MP4,1 (or 5,1) PSU, right now I'm working on an unbelievably crappy PSU a friend of mine gave me as a gift:



I see ~20 caps to replace, this is, at most, a 1-2 hours work if you take it very very slowly.

The caps themselves, even the big ones, even going for *really* good ones, won't cost more than 10€ in total.

Let's say that the Mac's PSU is incredibly overengineered and has 40 caps, you're still looking at a 2-3 hours max work + 20€ in caps.

Let's even go for the worst case scenario, where ALL the regulators have blown up, you have to pick new regulators and apply new thermal paste between them and the heatsink and whatever... really, I can't see this going north of 150€ total.

If someone is asking you for 300$, unless they include a 2 years warranty or something like that, is highway robbery, IMHO.
 
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tsialex

macrumors 603
Jun 13, 2016
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Well, I've never opened a MP4,1 (or 5,1) PSU, right now I'm working on an unbelievably crappy PSU a friend of mine gave me as a gift:



I see ~20 caps to replace, this is, at most, a 1-2 hours work if you take it very very slowly.

The caps themselves, even the big ones, even going for *really* good ones, won't cost more than 10€ in total.

Let's say that the Mac's PSU is incredibly overengineered and has 40 caps, you're still looking at a 2-3 hours max work + 20€ in caps.

Let's even go for the worst case scenario, where ALL the regulators have blown up, you have to pick new regulators and apply new thermal paste between them and the heatsink and whatever... really, I can't see this going north of 150€ total.

If someone is asking you for 300$, unless they include a 2 years warranty or something like that, is highland robbery, IMHO.
You would be surprised when you open a Mac Pro PSU, it’s nothing like a PC PSU and incomparably complex, with two big PCBs. To recap a Delta PSU you need SMD gear, but a ACBell is thru-hole. To access some of the caps, you need to remove the heatsinks, just this is an hour of work.

Capacitors are a lot bigger and costlier than the usual PC PSU. You should open and inspect your PSU before pre-formulating ideas.
 

tsialex

macrumors 603
Jun 13, 2016
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Has anyone built a kit to convert a PC PSU to work on a mac pro?
MP4,1 and MP5,1 PSUs are managed by the SMC. You could probably make a Mac Pro backplane to work with a pair of lab power supplies and some interfacing for the SMC part for backplane repair purposes, but I doubt that this idea is useful to anyone wanting to interface a PC PSU with the SMC. 1000+ W PC PSUs are not cheap anyway, just buy an used PSU.
 
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donluca

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Jul 30, 2018
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You would be surprised when you open a Mac Pro PSU, it’s nothing like a PC PSU and incomparably complex, with two big PCBs. To recap a Delta PSU you need SMD gear, but a ACBell is thru-hole. To access some of the caps, you need to remove the heatsinks, just this is an hour of work.

Capacitors are a lot bigger and costlier than the usual PC PSU. You should open and inspect your PSU before pre-formulating ideas.
Thanks for the input! Now I'm very curious to dig into my cMP Pro PSU.

SMD caps, eh? That's a big no-no, it's a huge hassle working with SMD caps and I gotta admit I've *never* seen any kind of PSU with *only* SMD caps. How in the world do they put the big electrolytic filter caps in SMD? Plastic/Polyester/Polypropylene, alright but those are virtually indestructible, I've yet to find one of those dead.

"Just buy a used PSU" it's not a 100% valid solution because it would still be a 10 years old and you're still running the risk of having it die on you in just 1 or 2 years, depending on various factors such as heat and usage.

I'll be exploring the recap option and see what I can come up with. Granted, if it's truly 100% SMD there's no way in hell I'll ever do a recap of the thing.
 

AlexMaximus

macrumors 6502a
Aug 15, 2006
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Thanks for the input! Now I'm very curious to dig into my cMP Pro PSU.

SMD caps, eh? That's a big no-no, it's a huge hassle working with SMD caps and I gotta admit I've *never* seen any kind of PSU with *only* SMD caps. How in the world do they put the big electrolytic filter caps in SMD? Plastic/Polyester/Polypropylene, alright but those are virtually indestructible, I've yet to find one of those dead.

"Just buy a used PSU" it's not a 100% valid solution because it would still be a 10 years old and you're still running the risk of having it die on you in just 1 or 2 years, depending on various factors such as heat and usage.

I'll be exploring the recap option and see what I can come up with. Granted, if it's truly 100% SMD there's no way in hell I'll ever do a recap of the thing.

Unfortunately I have to confirm the recommendation from Alex. Not long ago, I had my 5.1 PSU apart for the pixlas upgrade. Of course I was curious and opened it up for further inspection. I am an electrical engineer by trade, but I absolutely do not see any way how to effective prevent a failure by replacing capacitors. Don't fix something that's not broken.
First of all, this scenario is based on the speculation that one of the main failure reasons are capacitors. Of course most people on this forum may remember the good old PowerMac G5 area where we had some issues with that. But at that time this was because of production failures or failures in product development on the side of the parts supplier across several products and brand names. - not aging through use. Who's say's that's the an issue or risk a whopping 15 years later? I doubt it. Aging can come into the mix, but the question is when. In my personal opinion, the biggest failure risk is in the tyristor/mosfets parts on that aluminium heatsink. (German - Leistungselektronikbauteile) This is usually the prime candidate for failure and fails usually a lot sooner than any capacitor has a chance to dry out. In industrial applications you would loose easily three thyristor elements or more before a single capacitor says goodbye. Even the cooling fan motor or the cooling fan motor bearings might be a higher risk.

If you want to ensure a long shelve live for your 5.1 PSU, there are many other things you can do. Here is my recommendation for you:

- Get informed about the Power/Net Quality of your local power provider. Sometimes they are obligated to monitor a minimum standard. If they are clueless, direct them to the page down below. If they have an ISO-9000 Quality System in place, they are required to show you (or a specialist) the latest report about net quality.
- Get informed about past power spikes in your area. You may contact insurance companies as well, to track down past occurrences such as lightning strikes or power plant shutdowns.
- Make sure you have proper lighting protection installed at your home to ensure a minimum of power spike protection.
- Get informed about UPS Systems to insure clean power as a preventative effective measure in case of power failure or power loss.

https://www.fluke.com/en-us/products/condition-monitoring/power
 

donluca

macrumors regular
Original poster
Jul 30, 2018
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That's some solid advice, although, in my humble experience, recapping has been one of the best practice for old electronics to prevent breakdowns.

I must admit I'm now really curious, as I've never seen a mosfet or thyristor going bad on their own. I've seen some blown up due to other circumstances, but in 99,99999% of the cases, it would be electrolytics going bad long before any other IC. I've had some cases of *very* old carbon resistors which had their resistance higher (even twice or more sometimes), but rarely on stuff made post '80s. I've seen relays going bad, switches and loads of potentiometers and sometimes regulators (although it's often due to poor cooling).

This whole topic has piqued my interest, guess I have a nice little project on my hands during this summer holiday.

EDIT: I double down on the UPS suggestion: those are real life savers. Better to have your UPS die then your precious Mac Pro.
 

Macschrauber

macrumors 6502
Dec 27, 2015
492
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I do electronic repairs for living for about 30 years.

If you want to investigate then take the psu apart, uncharge the high voltage caps and check all caps with an ESR meter.

Did that with MP 1.1 PSUs a while ago but did not find any caps what urged replacement. Ended by curing the PSUs by replacing the low voltage boards. Had a bunch of dead PSUs so it took the cheap way :)

Would love to see someone curing 4.1/5.1 PSUs.

Still got no dead PSU of that Mark in my hands to dig into. If someone in Europe, Germany exactly, donate me a dead PSU I can give it a closer look.
 
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donluca

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Jul 30, 2018
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Did that with MP 1.1 PSUs a while ago but did not find any caps what urged replacement. Ended by curing the PSUs by replacing the low voltage boards. Had a bunch of dead PSUs so it took the cheap way :)
That's very impressive, to say the least, for a PSU older than 10 years.
I guess you've took out the caps from the circuit to measure the ESR right? Otherwise you might have parasitic resistance due to their placement in the circuit.

Also, bear in mind that ESR doesn't tell the whole story, sometime you have to check the straight capacitance to get a good idea of the condition of the capacitor. I've had some (rare, gotta admit) cases where a bad cap measured ESR just fine, but it was as dry as a Martini.

Definitely keep an eye on this thread, I'll probably open up the 4,1 PSU and give a good look this summer.
 

startergo

macrumors 65816
Sep 20, 2018
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I do electronic repairs for living for about 30 years.

If you want to investigate then take the psu apart, uncharge the high voltage caps and check all caps with an ESR meter.

Did that with MP 1.1 PSUs a while ago but did not find any caps what urged replacement. Ended by curing the PSUs by replacing the low voltage boards. Had a bunch of dead PSUs so it took the cheap way :)

Would love to see someone curing 4.1/5.1 PSUs.

Still got no dead PSU of that Mark in my hands to dig into. If someone in Europe, Germany exactly, donate me a dead PSU I can give it a closer look.
Once i took apart the PSU and started measuring with the ESR meter the big capacitors and some medium ones. I did not find anything out of tolerance. Now I am thinking more about thyristors (or any other switching elements) being faulty. Anyway without a wiring diagram it would be really hard. I was also thinking about smart tweezers.
 

Macschrauber

macrumors 6502
Dec 27, 2015
492
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That's very impressive, to say the least, for a PSU older than 10 years.
I guess you've took out the caps from the circuit to measure the ESR right? Otherwise you might have parasitic resistance due to their placement in the circuit.

Also, bear in mind that ESR doesn't tell the whole story, sometime you have to check the straight capacitance to get a good idea of the condition of the capacitor. I've had some (rare, gotta admit) cases where a bad cap measured ESR just fine, but it was as dry as a Martini.

Definitely keep an eye on this thread, I'll probably open up the 4,1 PSU and give a good look this summer.
Yes, ESR dont tells the whole story, frequency, temperature, pulses, etc etc.

I bet there are caps what not measure like new, cant be after all those years. But in my cases that had to do with the low voltage board (2006 PSU) - cause all PSUs I repaired worked after replacing them. So simply no need to dig in further at that time.
 

donluca

macrumors regular
Original poster
Jul 30, 2018
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Thanks for reporting, would you mind telling us how many years did it have before it was gone for good? And how frequently you used the mac?

I'd love to start looking at some stats and see if there's a pattern from which we can make some (very) broad assumptions about a Mac Pro PSU life estimate.
 

Macschrauber

macrumors 6502
Dec 27, 2015
492
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One very important data point on a switching supply is if it runs on 110 or 230 Volts. As pulse width should be longer the primary part should run hotter on 110 Volts.