Tips Reform Mother Board Electrolytic Capacitors?

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Tips Reform Mother Board Electrolytic Capacitors?

Postby kenitholson » Mon May 09, 2016 8:18 am

Recently I inherited an old Dell Dimension 2400 PC http://www.cnet.com/products/dell-dimension-2400/specs/ that had been in storage for many years.

I remember reading that audio amps that have been in storage for a long time should have the electrolytic capacitors reformed. http://www.vcomp.co.uk/tech_tips/reform_caps.htm

Did a forum search using "reform electrolytic capacitors" to check if others have asked this question but got "No suitable matches were found".

Appreciate any tips!!!

Thanks,

Ken
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Re: Tips Reform Mother Board Electrolytic Capacitors?

Postby Karlsweldt » Mon May 09, 2016 4:54 pm

More fable than fact, about "reforming" capacitors. Maybe the older ones of 40 years or more ago, but today's product is of better quality and longevity. That is ASIDE from the plague of bad capacitors that ravaged the electronics industry!
Best to inspect each capacitor for domed top, leaning excessively, or signs of leakage. Then they are bad, and must be replaced with new of identical voltage and capacitance. I would also scrutinize all capacitors in that Dell system before firing up. Same with its PSU. Heat is the worst enemy of capacitors, causing them to vent and dry out. The temperature rating for most applications is 85°C, for computer and higher temperature uses, must be 105°C.
The primary purpose of a capacitor is to absorb voltage peaks (ripples) in power supplies, and provide an almost pure DC source.
The other purpose of a capacitor is to safely pass AC signals to other circuits, without altering voltages of those other circuits.
An "AC" capacitor is simply two identical DC capacitors in the same shell, negative terminals mated. The positive terminal of each is external. There is no polarity.
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Re: Tips Reform Mother Board Electrolytic Capacitors?

Postby Twisty » Mon May 09, 2016 7:46 pm

That audio thing is talking about very old huge capacitors that generally need to be in well matched pairs. Not the hundreds of little caps all over your Dell. If i were you - I would clean tbe dust out, give it a visual inspection and then switch it on. If it doesn't work then that is the time to worry about what is wrong and how to fix it.

Computers tend to store pretty well i would rate the top potential issues as
    1. thermal paste drying out and becoming less effective
    2. Oil drying out on fan bushings/bearings
    3. Stored in damp causing corrosion to contacts etc
    4. Become a antiquated and worthless (morrs law)

As an aside, whilst it is possible to create a bipolar (ac) capacitor from two electrolytics they are more commonly just made from a non eleytrolytic material (e.g ceramic)
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Re: Tips Reform Mother Board Electrolytic Capacitors?

Postby evasive » Tue May 10, 2016 11:44 pm

This for once Dell used Rubycon caps so that is most likely not going to be an issue. Just make sure to unplug the system whenever there's a thunderstorm nearby, they are easily killed by ESR spikes it seems, nobody knows why.
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