Capacitor curiousity

[Bobdee]

Hello Guys
Can you help me, I removed 4 caps from old m/board brand Ost series RLX 3300uF 6.3V they appeared to look good, bungs fine, no bulging.
When measured with ESR meter several times, over several days at room temp, they read around 4400uF and 0.00 esr, no doubt caput but what causes the caps to go high, well above there tollerance and reduce in ESR and still look good.
The caps I normally remove that are bad go down in capacitance and up in ESR as you know.
Can you tell me why they go like this???
Does this happen often???
Will look forward to your replies
many thanks
bobdee

[Wizard]

Re: Capacitor curiousity

ESR is where water and chemical are, basically the electrolyte formulation comes from. If not right, poor seal or combination of many, the electrolyte dry out and ESR rises. Sometimes violently enough that tops or bung blows out, sometimes boiling and pressure builds quietly then gently pop or with a noise.

And if you see listed of brands like OST it's granteed to go bad with time and use.

Cheers, Wizard

[i4004]

Re: Capacitor curiousity

>no doubt caput

what is caput?
it seems to me you've taken out the good caps and now you're wondering how come they're good.

[gdement]

Re: Capacitor curiousity

>no doubt caput

what is caput?
it seems to me you've taken out the good caps and now you're wondering how come they're good.

4400uF is out of tolerance. But maybe they're not particularly bad other than that.

[Bobdee]

Re: Capacitor curiousity

Hi again Guys
Thanks for input, so you think these caps could still be good, if thats the case they must have been manufactured with way over tollerance, or something made them go that way, is thats possible???.
Also the 0.00 ESR, I am sure I read in a capacitor thread (Ithink byTopcat) a while back, that it is not possible to have a good cap with 0.00 ESR, so I still find that very strange why these caps are like this.
Look forward to revised, and new input from you.
Many Thanks
Bobdee

Sorry about the caput, should have been kaput, meaning had it, gone bad,dead ect

[i4004]

Re: Capacitor curiousity

>or something made them go that way, is thats possible???.

i doubt it.

other thing 0.00 esr may suggest is short circuit, but if it's that than capacitance would be at 0.
(use normal multimeter to test for that...)

[willawake]

Re: Capacitor curiousity

likely esr meter cannot measure low enough

[Bobdee]

Re: Capacitor curiousity

Hi Guys
Tested with m/meter for shorts across terminals both ways, and terminals to casing, no shorts.

Also ESR meter is ATLAS esr60, it measures from 0 to 20 Ohms, resolution as low as 0.01, and if capacitence more than 20 Ohms reads >20 Ohms, did a probe compensation test on meter, tested OK.

Bobdee

[kc8adu]

Re: Capacitor curiousity

iirc in the first stages of cap death the uf value rises.

[Bobdee]

Re: Capacitor curiousity

Hello again Guys
At first I thought iirc that was mentioned by Kc8adu was a chemical component inside capacitor untill I googled it.
Found abbreviation meaning, IF I Remember Correctly, it was new to me, but I will remember that one.

I think hes hit the nail on the head with his explanation, I can certainly go with that, and bin the caps as kaput, unless anyone has more to add.

I would like to thank everyone for there input, much appreciated, I have learned from this experience.
Bobdee

If anyone has a link to read up on this rise in capacitance, I would like to hear from you.