Author Topic: Rebuild a power supply?  (Read 2148 times)

Offline nanopico

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Rebuild a power supply?
« on: November 08, 2016, 09:28:05 PM »
Has anyone rebuilt/refurbished/restored a power supply?
I have this Dual 867mhz MDD with a bad PSU.  I'm considering rebuilding it for fun.
Just wondering if anyone else has done this and can provide any pointers.
If it ain't broke, don't fix it, or break it so you can fix it!

Offline Knezzen

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Re: Rebuild a power supply?
« Reply #1 on: November 08, 2016, 11:04:47 PM »
A friend of mine resurrected a Xserve G5 PSU with a simple recap.
It was stone dead before that.

Offline nanopico

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Re: Rebuild a power supply?
« Reply #2 on: November 09, 2016, 06:17:32 AM »
A friend of mine resurrected a Xserve G5 PSU with a simple recap.
It was stone dead before that.

Do you know if it hummed and sort of chirp/clicked when plugged in but not powered on?
If it ain't broke, don't fix it, or break it so you can fix it!

Offline Texas_RangerAT

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Re: Rebuild a power supply?
« Reply #3 on: November 19, 2016, 01:40:54 PM »
I've never done it myself but had an MDD power supply rebuilt. They tend to fail a bit more spectacularly than just going out, mine had an exploded varistor and probably some hidden damage.

Power supply failure seems to be a common denominator of nearly all computer systems, probably at least partly thanks to crowded switching-mode power supplies where electrolytic caps and other components get fairly hot.

Offline mrhappy

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Re: Rebuild a power supply?
« Reply #4 on: November 20, 2016, 09:54:03 AM »

Do you know if it hummed?

Maybe it just doesn't know the words???

Helpful I know!😁

Offline nanopico

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Re: Rebuild a power supply?
« Reply #5 on: November 21, 2016, 12:26:17 PM »

Do you know if it hummed?

Maybe it just doesn't know the words???

Helpful I know!😁

Well it's a bit tone def and rhythmically challenged.
If it ain't broke, don't fix it, or break it so you can fix it!

Offline MacOS Plus

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Re: Rebuild a power supply?
« Reply #6 on: November 21, 2016, 08:26:40 PM »
  I'd like to know the chances for success on this too, seeing as I have two dead MDD supplies also.

Offline nanopico

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Re: Rebuild a power supply?
« Reply #7 on: November 21, 2016, 08:34:03 PM »
  I'd like to know the chances for success on this too, seeing as I have two dead MDD supplies also.

I'm at a point where it is just sitting there so if I mess it up I really don't care.
If it ain't broke, don't fix it, or break it so you can fix it!

Offline Texas_RangerAT

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Re: Rebuild a power supply?
« Reply #8 on: December 24, 2016, 03:19:05 AM »
I'm in a somehat similar situation now, except I'm considering going through a power supply that still works to keep it from failing in the first place. At the very least I'll replace all electrolytic caps except for any on the primary (usually a 47 F/400 V) but I'll try to find out if there's anything else likely to fail in a catastrophic manner.

As long as you're aware of the fact that those primary capacitors can hold a potentially deadly charge for a long time I can't see how you could damage a power supply any further (I'd suggest bleeding the cap via a 100 kΩ resistor) but depending on how much you know about diagnosing power supplies you might end up replacing a lot of stuff without actually fixing anything. From your questions I guess you don't really know more than I do and unfortunately that's very little. I recently tried to do a - fairly straightforward - Amiga 500 power supply and after having replaced all electrolytic caps, the fuse and a physically broken resistor I still haven't gotten anywhere. I suppose the next step would be measuring output voltages and trying to determine if the switching circuit does anything at all and if it does, which voltage is affected. Without schematics and intimate knowledge of the workings of a power supply in general I'm afraid it'd still be hard to figure out which parts do what and are likely culprits.

By now there isn't much left of that Amiga brick so I might get it done - basically I'm down to something like five small transistors, two voltage regulators (probably one for 5 and 12 V each, haven't bothered to check the numbers, just saw they started with LM), a thyristor and two parts I haven't been able to identify because they're in such crowded places I can't read anything on them. That's seven parts, probably a few cents each so I suppose in theory I could just replace all of them - in a worst-case scenario only to find out that the transformer is blown open.

The MDD power supply is considerably more complex IIRC so there might be a lot more that could fail. If I find out any details I'll let you know!

Offline IIO

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Re: Rebuild a power supply?
« Reply #9 on: December 24, 2016, 08:06:26 AM »

Do you know if it hummed and sort of chirp/clicked when plugged in but not powered on?

thats what most of my G4s psu do ;)
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Offline s0s

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Re: Rebuild a power supply?
« Reply #10 on: December 27, 2016, 09:54:45 PM »
Has anyone rebuilt/refurbished/restored a power supply?
I have this Dual 867mhz MDD with a bad PSU.  I'm considering rebuilding it for fun.
Just wondering if anyone else has done this and can provide any pointers.
Unless you want to rebuild it merely to learn electronics skills, I would get a new one. Most computer manufacturers use the cheapest components they can get so they can maximize profit. A high-quality PSU can prolong the life of your system. As mentioned here, http://www.tomshardware.com/forum/id-2547993/psu-tier-list.html

Quote
Components - Higher quality components means more stable functionality, thus longer life on power supply and components of PC. Low quality components can affect the life of the unit and all components of your PC.

You can find some high-quality PSUs that are platinum rated for not much money. Many of the PSUs manufactured in China are crap.

Offline nanopico

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Re: Rebuild a power supply?
« Reply #11 on: December 28, 2016, 07:31:37 AM »
Has anyone rebuilt/refurbished/restored a power supply?
I have this Dual 867mhz MDD with a bad PSU.  I'm considering rebuilding it for fun.
Just wondering if anyone else has done this and can provide any pointers.
Unless you want to rebuild it merely to learn electronics skills, I would get a new one. Most computer manufacturers use the cheapest components they can get so they can maximize profit. A high-quality PSU can prolong the life of your system. As mentioned here, http://www.tomshardware.com/forum/id-2547993/psu-tier-list.html

Quote
Components - Higher quality components means more stable functionality, thus longer life on power supply and components of PC. Low quality components can affect the life of the unit and all components of your PC.

You can find some high-quality PSUs that are platinum rated for not much money. Many of the PSUs manufactured in China are crap.

If you have a reference for an affordable power supply for the MMD that would be great.   
They are not a standard power supply.  They have a different shape and and also a 25v rail for the ADC port. I use an ADC.

Electronic skills aren't an issue. I was just curious if anyone here had done it before.
If it ain't broke, don't fix it, or break it so you can fix it!

Offline s0s

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Re: Rebuild a power supply?
« Reply #12 on: December 28, 2016, 10:44:16 AM »
Well I had a bookmark from several years ago for a MDD PSU on newegg. I should have checked it before I posted, because it's not there anymore. I just remembered that I found one once, back when I was thinking about buying a non-working MDD, thinking it would be cheaper to fix myself than buy a working one.

Offline nanopico

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Re: Rebuild a power supply?
« Reply #13 on: December 28, 2016, 01:35:15 PM »
Well I had a bookmark from several years ago for a MDD PSU on newegg. I should have checked it before I posted, because it's not there anymore. I just remembered that I found one once, back when I was thinking about buying a non-working MDD, thinking it would be cheaper to fix myself than buy a working one.

Almost all of them are about $100 now.  Not really what I want to spend and it's not really a machine I need to have working so it's not worth the money.
If it ain't broke, don't fix it, or break it so you can fix it!

Offline DieHard

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Re: Rebuild a power supply?
« Reply #14 on: December 28, 2016, 02:20:25 PM »
Many, Many MDDs have been ewasted because of a bad Power Supply. 

Many more have also been ewasted for the seller to sell the PS only on ebay at the same price (and easier to ship) than the whole unit.

We must protect this "en-dangered" species of G4 from hunting them for their PS blubber... this is an Atrocity of the modern world and MUST STOP NOW.

Well, anyway, the guy that used to make the translation PS harness from MDD to standard PS has long since faded into obscurity. Please let us know if he is still alive.  Many have tried to email him and never got an answer back
http://atxg4.com/mdd.html

Offline Apfel

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Re: Rebuild a power supply?
« Reply #15 on: December 28, 2016, 04:13:40 PM »
...

Well, anyway, the guy that used to make the translation PS harness from MDD to standard PS has long since faded into obscurity. Please let us know if he is still alive.  Many have tried to email him and never got an answer back
http://atxg4.com/mdd.html
using the wiring schemes there for modding an ATX-Power Supply there is a guide on how to fit the ATX PSU in the original place of the MDD-PSU here http://aquamac.proboards.com/thread/1174?page=1#8403 post #8 very last line, where he lists the video links (see only part3, if in a hurry).

Offline s0s

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Re: Rebuild a power supply?
« Reply #16 on: December 30, 2016, 11:06:23 AM »
Many, Many MDDs have been ewasted because of a bad Power Supply. 

Many more have also been ewasted for the seller to sell the PS only on ebay at the same price (and easier to ship) than the whole unit.

We must protect this "en-dangered" species of G4 from hunting them for their PS blubber... this is an Atrocity of the modern world and MUST STOP NOW.

Well, anyway, the guy that used to make the translation PS harness from MDD to standard PS has long since faded into obscurity. Please let us know if he is still alive.  Many have tried to email him and never got an answer back
http://atxg4.com/mdd.html
Very good endangered species analogy, and I totally agree!

Offline nanopico

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Re: Rebuild a power supply?
« Reply #17 on: January 28, 2017, 02:22:32 PM »
Had a day to get around to doing all sorts of fun things with my machines waiting to be set up and stuff.
And this was on the list.
All I can say, is that these power supply are a royal pain in the ass to disassemble.
If it ain't broke, don't fix it, or break it so you can fix it!

Offline GaryN

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Re: Rebuild a power supply?
« Reply #18 on: January 28, 2017, 02:33:30 PM »
What the world needs is a "Magic Potting Compound Remover"

Offline nanopico

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Re: Rebuild a power supply?
« Reply #19 on: March 01, 2017, 09:54:50 AM »
And now I am giving in.  Too many projects, too little time. (I'm sure most of you would understand that one).
I bought a new PSU for the MDD.  Maybe someday I'll get to rebuilding the old one.
If it ain't broke, don't fix it, or break it so you can fix it!

Offline InspectorG

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Re: Rebuild a power supply?
« Reply #20 on: March 01, 2017, 06:49:32 PM »
And now I am giving in.  Too many projects, too little time. (I'm sure most of you would understand that one).
I bought a new PSU for the MDD.  Maybe someday I'll get to rebuilding the old one.

Did you buy an original Apple PSU (used I'm assuming) or something third-party?

Offline nanopico

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Re: Rebuild a power supply?
« Reply #21 on: March 01, 2017, 08:52:18 PM »
And now I am giving in.  Too many projects, too little time. (I'm sure most of you would understand that one).
I bought a new PSU for the MDD.  Maybe someday I'll get to rebuilding the old one.

Did you buy an original Apple PSU (used I'm assuming) or something third-party?
Original Apple PSU. Found a new old stock.  We'll see how well that works out.
If it ain't broke, don't fix it, or break it so you can fix it!