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Muh-soggy-knee -
Re: Why does a cap vent?
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Vented gas caps work by a pressure activated one-way release valve. When pressure builds to a certain point it opens the valve. This allows a small amount of air to be released into the gas tank line.Comment
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Re: Why does a cap vent?
^ I'm afraid we're talking electronics cap-acitors here, not vented fuel tank caps
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Re: Why does a cap vent?
They discovered that venting caps were preferred over the exploding ones.
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Re: Why does a cap vent?
The only time I saw a cap explode was back in the 80s when building a 286 pc clone. They were into using little tantalum caps all over the board then, not all the little cans we see now. As soon as I applied power to the board one of those little puppies went off like firecracker! Sure glad the top didn't hit me because it ricocheted all over the shop like a tiny bullet! Smelled like hell too!Comment
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Re: Why does a cap vent?
That is not to say I have not seen exploded caps after the actual explosion, that is the only time that I saw one in the act of exploding.
I had a blonde Fender Tremolux Amp that the big power supply caps blew out after a very hot and long day in the back window of a VW microbus and being set up on a very hot outdoor stage and powered on. I heard and smelled those caps blow but couldn't see them. It was a mess. That is why they make them with vents now.Last edited by SteveNielsen; 02-02-2014, 10:24 AM.Comment
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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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