Electrolytic cap's went bad but never used ?

Thread Starter

DarthVolta

Joined Jan 27, 2015
150
I have a little computer ATX PSU I want parts from, and it's supposed to be new, and I had a look inside and 1 cap has leaked and other's are bulging. I gather that's H2 gas building up.

But do they really go bad and break down on their own like that if they are never used and just sitting there ??

I've taken apart a lot of things, and don't remember actually having bulging caps, and lots of them were way older than this, I guess I've been lucky.
 

jpanhalt

Joined Jan 18, 2008
8,076
I have a little computer ATX PSU I want parts from, and it's supposed to be new, and I had a look inside and 1 cap has leaked and other's are bulging. I gather that's H2 gas building up.

But do they really go bad and break down on their own like that if they are never used and just sitting there ??

I've taken apart a lot of things, and don't remember actually having bulging caps, and lots of them were way older than this, I guess I've been lucky.
Yes, electrolytic capacitors have a limited shelf-life when not used. That is particularly true of wet electrolytic like the ones you describe. See here: https://passive-components.eu/get-the-lowdown-on-shelf-life-and-storage-of-capacitors/
 

Thread Starter

DarthVolta

Joined Jan 27, 2015
150
I fixed re-capped a few things, I'm pretty new in general. I can't remember any bad caps I noticed by looking, except ones I blew up by accident early on I suppose.

This was a gift, he said it was never used. It's a pretty cheap 350W unit, I haven't found a date code yet, no SATA cables on it, so 2000's. era

4 bad TeaPo caps, and 1 bad CapXon, I haven't checked any ESR's yet.

As a project I'm stripping it right down so I can understand more details of these types of supplies. I've learned a lot just past year. I'd like to take a little supply like this, and see how much lower and higher the voltage rails could safely go. I'd be happy with 10-15V as the 12V rail. This one uses a pretty basic PWM controller chip compared to bigger PSU's. I could use some SMPS SG3524 PWM chips I have, that can be controlled.


Holy cow it has several th-hole leads that were bent down super close to other tinned traces. Like insanely close across the tank cap trace even. I can't see how that could have been me just de-soldering some stuff. Glad I never plugged it in, since I fully assumed it was fine. But I intended to dismantle it, since it's a smaller, and more discrete parts unit.
 
Last edited:

bertus

Joined Apr 5, 2008
20,102
Hello,

Here is a part of the reliability page on the capsite:

A problem rarely mentioned is the quality of many Chinese parts in general. Aluminum electrolytics are high-volume, low-margin parts and if the small Chinese regional producers expect to compete with Japan and the larger Chinese companies they must cut costs to the bone.

The low cost of Chinese labor is not enough, their competitors are generally much more automated with the Chinese using older second-hand equipment.

So how can they compete?

Use lower purity aluminum for the case and foil. This can result in cracks when the case is formed and corrosion in critical places.
The use of cheap natural rubber plugs instead of synthetics like EPDM. This can result in early loss of water from the electrolyte and even leakage.
Use lower cost plated foil. Instead of foil with a 10-20% voltage margin, use 25V foil for a 25V capacitor.
Dilute the electrolyte with extra water.
Reduce equipment maintenance. It take time and expertise the Chinese do not always have.
Little product quality control. Again, that takes time and money.

The result is parts with lower reliability and shorter life. It's hard for the user to know. Testing aluminum capacitors is not easy. You can use a cheap LCR meter to measure the uF value. A good LCR meter (expensive) will tell you the value and things like dissipation factor and ESR, but life testing requires thousands of hours and expensive equipment.

I have noticed that a few Chinese manufacturers of cheap electronics, like audio boards, say they use Japanese electrolytes.

http://www.iequalscdvdt.com/Reliability_1.html

Bertus
 

MisterBill2

Joined Jan 23, 2018
4,004
Hello,

Here is a part of the reliability page on the capsite:

A problem rarely mentioned is the quality of many Chinese parts in general. Aluminum electrolytics are high-volume, low-margin parts and if the small Chinese regional producers expect to compete with Japan and the larger Chinese companies they must cut costs to the bone.

The low cost of Chinese labor is not enough, their competitors are generally much more automated with the Chinese using older second-hand equipment.

So how can they compete?

Use lower purity aluminum for the case and foil. This can result in cracks when the case is formed and corrosion in critical places.
The use of cheap natural rubber plugs instead of synthetics like EPDM. This can result in early loss of water from the electrolyte and even leakage.
Use lower cost plated foil. Instead of foil with a 10-20% voltage margin, use 25V foil for a 25V capacitor.
Dilute the electrolyte with extra water.
Reduce equipment maintenance. It take time and expertise the Chinese do not always have.
Little product quality control. Again, that takes time and money.

The result is parts with lower reliability and shorter life. It's hard for the user to know. Testing aluminum capacitors is not easy. You can use a cheap LCR meter to measure the uF value. A good LCR meter (expensive) will tell you the value and things like dissipation factor and ESR, but life testing requires thousands of hours and expensive equipment.

I have noticed that a few Chinese manufacturers of cheap electronics, like audio boards, say they use Japanese electrolytes.

http://www.iequalscdvdt.com/Reliability_1.html

Bertus
Many folks consider that ALL aluminum electrolytic capacitors have a limited lifetime. AND even truly never used filter capacitors do deteriorate with time.
Consider that the typical failure of a computer monitor is in the capacitors of the back-lite power supply.
 

Mario87

Joined Sep 9, 2019
2
Unused capacitors are more likely to fail than ones that have been used moderately. Capacitors are not items that like to sit around for years without usage. Just like batteries, it's best to charge and discharge batteries regularly instead of keeping them constantly full or empty, same applies to electrolytic caps, leaving them unused for long periods does them more harm than good.
 
Top