bad panny fj. low capacitance, high vloss. what happened?

[ChaosLegionnaire]

recently, i tested some panny fj caps that i pulled from an asus a8v board some years back. these caps are 820 µf 6.3v rated and they all tested low capacitance with a reading of around 550 µf with a vloss of 5%. the esr tested normal tho.

these caps were used as general filter caps around the board for the minor rails. none of the caps show any signs of bulging. it should be noted the board was used with a capxon psu which seems to output a ton of ripple making the board unstable and failing to boot after a year of use.

so my question is what happened internally to the panny fj caps to make them low capacitance and high vloss? my assertion is that the excessively high ripple would make the electrolyte evaporate due to internal heating from what i know but none of the caps show any signs of bulging (there are over 20 of them!) so im not sure if my hypothesis is correct. so i guess these fj caps are drying out internally if they exhibit low capacitance and high vloss due to loss of electrolyte? it seems like caps only bulge if heat abused but not if electrically abused. need to know if my understanding of all of the above is correct so i can avoid this type of failure in future and not use junk failing psus and killing my mobos. thanks.

[stj]

Re: bad panny fj. low capacitance, high vloss. what happened?

nothing lasts forever,
i have seen pany FC leak at the leads multiple times,
and had a ruby MBZ explode because the board had not been powered for several years.

[Topcat]

Re: bad panny fj. low capacitance, high vloss. what happened?

I've pulled lots of bad pannies out of Dell systems. They aren't indestructible.

[Wester547]

Re: bad panny fj. low capacitance, high vloss. what happened?

Here are three posts documenting silent FJ failures:

https://www.badcaps.net/forum/showpo...77&postcount=1
https://www.badcaps.net/forum/showpo...&postcount=241
https://www.badcaps.net/forum/showpo...90&postcount=2

Low capacitance and in-spec ESR / high leakage current could denote that the anode foil has degraded. Capacitance depends upon the thickness of the anodic oxide film and how well the anode foil is formed and etched (some electrolyte is also necessary). Liquid electrolytics don’t need to experience thermal duress to bulge - overvolt one, reverse polarize one, manufacture one with an unstable electrolytic formula (KZG and KZJ) or shoddy raw materials (many a bad brand), and hydrogen gas will form (and a hiss or a bang will likely precede that proviso if it happens quickly enough).

My understanding is that the Dell systems of old, whether they are USFF, SFF, slim desktops, or even mid towers, tend to run on the hot side by default, so I’m not surprised that even Panasonics would eventually fail there. I’ve also kept wary of Panasonic FC leaking from the bung - I don’t know if it’s because their bungs are just softer and don’t take well to heat or if they’re simply decomposing over time. I consider Rubycon MBZ exploding after years of storage to be a tad more concerning. I’ve seen that happen lots with Nichicon HMs made before the second quarter of 2005 (as well as various crap brands), but not with MBZ. I would be curious to know what output that MBZ was filtering, the PSU feeding it, its capacitance and voltage rating, date code, etc, if such details were committed to memory. I realize capacitors aren’t meant to sit on the shelf forever and that the oxide layer needs to be reformed after years of disuse, so it may have been a factor.

[stj]

Re: bad panny fj. low capacitance, high vloss. what happened?

the MBZ was on the5v rail and 10v rated,
i suspect it simply needed re-forming because it had sat with a load across the terminals for several years.

[ChaosLegionnaire]

Re: bad panny fj. low capacitance, high vloss. what happened?

ah well... i guess that means i just have to take very good care of and be very nice with my ultra-low esr lytic caps. keep them actively cooled with a fan near them and no junk cap psus. only ultra-low ripple jap cap psus. also have to take them out of storage every year or so to reform them so that they dont pop.

with all this "fragile glass construction" of ultra-low esr lytics, its no wonder they got deprecated in favor of polymers. maybe i should start polymodding some stuff i dont use often.