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How to fix a PSU

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a b ) Power supply
May 6, 2011 3:31:58 AM

Assuming you have awareness of electronic safety and basic soldering skills this is very easy. If you want to know about soldering and electronic safety I'm sure you know how to use google.

So my mother in laws Acer dual core pentium D computer was acting up, from slow operation, to intermittent freezing and hangs. I said id have a look for her. After cleaning out all the dust it was still a bit flakey. So i opened up the PSU to have a look, low and behold a bulging capacitor >



I removed the psu circuit board and tilted it on its side so i didnt have to remove the fan or anything. Take note of the markings and polarity of the old capacitor. This one was 10v 1000uf at 105 degrees C. So I removed it and replaced it with one i had around the workshop rated at 16v 1000uf at 105 degrees C. Its ok to replace with something of higher voltage just not lower, either way the new capacitor was exactly the same size so it fit just right. Removing the old capacitor I used pliers to grip it and held the soldering iron to the legs to melt the solder and wriggled it out. Inserted the new one and cut the legs to size. The next image shows the new cap soldered in place, the 2 shiny solder joints are the legs of the new cap.



Heres a pic of the new cap in place



Now the old PC runs flawlessly and all for about 15 mins work and what was probably a 10 cent capacitor. I know this article is not very comprehensive at all, it was just to show you it can be done without too much knowledge, and without a lot of effort. There are plenty of more detailed articles around if you want to look into doing this yourself one day. I also suggest practising removing and re-soldering capacitors from an old motherboard or something before you attempt this.

More about : fix psu

a b ) Power supply
May 6, 2011 10:31:20 AM

I'm totally going to try this on my mother-in-law's PC. :) 
a b ) Power supply
May 6, 2011 11:37:31 AM

lmao, yeah, if you try it first on the mother in laws PC you better be sure it works. unless she already hates you, then it doesnt matter if you stuff it up.
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a b ) Power supply
May 6, 2011 2:21:10 PM

^ Concur, and to iam2thecrowe very good explaination on How-to-do it.
Great fix, maybe, maybe not. It may have fixed it and it runs for the rest of the usable life of the computer, or it may have produced a time bomb waiting to take out the rest of the computer - but that could also be a good thing, reason to upgrade the system and mack the Mother-In-Law really happy.

Fixing is one part of the equation. How did you test the PSU after the fix? Requires an O'scope and loads for the various outputs. This is to verify that the PSU can still provide the regulation at rated loads with an acceptable ripple.
The electrolytic Capacitor is defective for a reason - Poor quality (most likely), or another component caused it to fail. In either case the failing capacitor caused excessive ripple and excessive leakage current which may, or may not have damaged (weaken) other components.
Would I recommend this fix, myself - No, but it is an individual call.

I have the qualifications:
.. Certified to solder/repair space flight hardware.
.. Taught power supply circuit analysis - series/shunt regulated and switching, was hired to work with the engineer who designed power supplies. Perform testing/calibrating of Power supplies.
.. Have my own digital O'scope
a b ) Power supply
May 7, 2011 4:51:21 AM

"The electrolytic Capacitor is defective for a reason - Poor quality" spot on, its an Acer PSU, and its also quite old.
"How did you test the PSU after the fix?" - ran 24 hr stress test which would have failed prior to the repair......... i have no oscilloscopes or anything. but its not like i modified it, i just replaced the bulging cap with one of the same spec but better quality and higher voltage tolerance. I have replaced blown caps plenty of times before (mostly in printer psu's and monitors) and never really had a problem. It isnt always a sure fix though, but sometimes its worth a shot. Will see how it goes over the next few weeks since she just got a new computer and gave me this one. will just use it as a spare second pc.
!