Originally posted by PeteS in CA
thank you for the analysis...do you know any good sites so i can read
about the composition of electrolyte?
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Re: Why does a cap vent?
quite interesting effect if they could lift off...
thank you for the analysis...do you know any good sites so i can read
about the composition of electrolyte? -
Re: Why does a cap vent?
1)What is the "X" mark or the "T" mark on the top of the caps? is this the escape door?
It's an intentional "weak" spot in the can. It make it less likely that the whole can will launch like a little rocket. The scorings vent at a fairly predictable pressure - electrolyte vapor and/or hydrogen. BTW, electrolytes with significant water content are not peculiar to crap caps: e.g. all Rubycon low impedance caps have significant water content, but Rubycon (the other two 'cons and Panasonic also) knows what to add to stabilize the electrolyte.
2)The electrolyte is it corrosive for our skin? is it dangerous to smell it?
As a whole, no, though I wouldn't use electrolyte as soap or a beverage.
3)do we know the chemicals it contains?
The basic ingredients are known publicly.
4) The thin metal film inside the cap what is it? aluminium or some other metal?
AluminumLeave a comment:
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Re: Why does a cap vent?
some stupid questions
1)What is the "X" mark or the "T" mark on the top of the caps? is this the escape door?
2)The electrolyte is it corrosive for our skin? is it dangerous to smell it?
3)do we know the chemicals it contains?
4) The thin metal film inside the cap what is it? aluminium or some other metal?
thank you...
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Re: Why does a cap vent?
both. electrolysis starts the bulging.as it dries out esr rises and heating occurs.as the vent opens and more electrolyte is lost the cap looses capacitance and goes open.Originally posted by Tom41Leave a comment:
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Re: Why does a cap vent?
I think it is the H2, wich is generated by a chemicall reaction of H2O and AL if no inhibiting additive is in the elektrolyt. The H2 would be collected at the top of the cap, abd if the pressure is high enough the safety vent will burst.Leave a comment:
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Re: Why does a cap vent?
The theory is that of a pressure cooker. They heat, things expand, have no place to expand to, and poof.....they vent. They do it faster with shoddier brands, as the electrolyte is water-based, and evaporates at temps a lot lower than good ones.Leave a comment:
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Why does a cap vent?
Like the title suggests, what exactly causes a cap to vent? Does it heat up and 'boil' the electrolyte? Does electrolysis occur and produce gas?
I vented a cap recently - by pumping 20v into the 10v-rated cap on reversed polarity
and the pic in my avatar shows the result. It 'exploded' with a load of smoke. The cap was very hot afterwards, so maybe it boiled?
Last edited by Tom41; 08-21-2006, 02:51 AM.
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got this tv from a friend who got a new one and didnt want to bother repairing this one.
he said it sometimes would just flash color patterns.
and sometimes it would just work
i figured it had some intermittent mainboard issue.
i stored it at home for a while before looking at it
when i plugged it in for the first time, i heard some popping noises
and then a big cloud of white smoke came out of the back of the tv!
i noticed the smoke didnt actually smell like anything. not like when an IC blows.
i unplugged it and took the back off and discovered... -
I just bought these from Mouser and upon closer inspection the area where the bung and leads meet has some dried green substance on it, presumably dried electrolyte. Is this normal?...
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I recently bought some Nichicon caps on eBay (yeah, I know). These are small 4x7 radial 16V 10uF caps. I feel they are fakes because the plastic pattern on the bottom and they don't have the X-vent stamped in the aluminum end and all the datasheets I have read indicate there is a vent(not exactly sure what series they are....or are supposed to be). I don't really care about the couple dollars wasted but when I let the seller know he thought they were real and he doesn't want to sell fakes. I thought I would do a little research and let him know. Is the lack of the characteristic X enough to prove... -
From what I've found, the endurance of a liquid electrolytic cap is determined by the loss of electrolyte. If a cap is rated for 1000 hours. That's typically for a straight run test. How would the life vary if the cap is intermittently heated to its rated temperature (105C). Maybe for an hour at a time then cooled back to 30-40C (just a random number). Would the life still be 1000 hours?
Does it make a difference in the life expectancy if the cap is heating from ripple current (internal heating) instead of from the external ambient temperature?
Why do polymer capacitors... -
Hello All, I have on the bench a couple of PSU's which have some failed Nichicon PL series caps. They didn't "puke" their guts through the top, but instead "diarrhea'ed" corrosive brown electrolyte through the bottom, down the legs and onto the board. On one cap, the electrolyte rotted the cap right off the board leaving 2 little stubs, and also corroded a trace on the foil side.
The PSU's are Power-One MAP series and are ringing-choke topology. The semiconductors have date codes in 1993. The PSU's were used in a commercial application, fan-cooled. They had failed...
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