Electronics > Beginners

What happens when you put an electrolytic capacitor the wrong way?

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Phaedrus:
Once had a 1200W SMPS left on a load tester idle, with just a 1A load @3.3V. It sat there maybe an hour, then out of nowhere--BOOM!!! The PFC capacitors, a pair of 560uF 420V numbers, both went nuclear! Unbelievable, that would happen with only about 20W of AC input (not very efficient at that low load). Still not sure what caused it; it was the first time this had ever happened, and the product was due to EOL, so the CEO told us not to waste time diagnosing. I disagreed, but followed orders.

Anyway, the whole lab stank like toad cheese for two whole days, even with the window open and a fan blowing. Disgusting.

HWM:
if Electrolytic capacitor was used in decoupling mounted in reverse polarity, will it explode immediately?

extide:
This is what happens

vk6zgo:
 Often, it will  go bang, but sometimes, nothing obvious will happen.

I was refurbishing a Sony BVM 2000 Monitor one time, & found a number of electrolytics on one board were installed "the right way round" according to the "silk screened" markings on the component side of the PCB, but reversed, according to the markings on the other side, as well as the schematic.

This device had been in service, meeting all specifications, for around 10 years!
Needless to say, I replaced them the right way around as per the schematic.

On another occasion, "in another place", I replaced all the electros (big ones) in a rack mounted PSU in an AM Broadcast Tx site "speech input room".
Unfortunately, it was a -24v supply, & I mindlessly fitted the caps as for a positive supply.

At turn on, there was a loud "Bang!" & the air was full of capacitor guts----it looked like it was snowing!

On another occasion, a trainee gave me his project (A Dick Smith Electronics kit), to check the wiring.
From a cursory inspection, all was well, right components, excellent soldering, & so on.
Having got my approval, he switched  it on.

There was a sound like a 0.22 rifle shot, & the case of an electrolytic blew its end open (It was a small  cap-- the big ones sounded like a shotgun)

Dear old DSE had marked the board wrongly, so I wouldn't have been able to pick it without a much closer look.
Even so, I think the trainee lost a bit of faith in my supervisory capacities!

Nerull:
http://youtu.be/HEc5Juq7TaQ?t=593

The Amiga CD32 came with capacitors installed backwards from the factory.

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