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Old 2nd Dec 2017, 10:27 pm   #42
Argus25
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Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,679
Default Re: Electrolytic capacitor fails after 1 hour in service!

Quote:
Originally Posted by kalee20 View Post
but known internal rejects, but a dishonest employee has intercepted them en route to the skip to flog them and make some easy money.
That is an interesting mechanism of how this could happen, if they made a mislabeled batch at the factory, say 16V caps labelled as 63V, or reverse polarity and put them in a dumpster out the back, they would look pretty attractive to anyone, not necessarily an employee. Then the person selling them might not have known there was an issue in the first place.

It is a big deal in the aviation industry how to dispose of faulty parts, often they end up getting recycled & sold as refurbished. Sometimes they mutilate them before dumping. There was a story about a helicopter blade(these things are worth 100's of thousands of $) being mutilated with multiple holes drilled in it. Someone found it, filled the holes with Bondofil, repainted it with a masterful black gloss coat and on sold it.

At least with axial electros the polarity is self evident due to the rubber seal. But radial ones it relies on the plastic cover being put on and labelled correctly.

Check the physical size of the caps against others, if its a mislabeled 16V one it should be physically smaller than a 63V one of the same capacity.

One thing I found recently with radial electros, if they have leaked electrolyte in the past (which can sometime not be easily optically visible) if meter probes are placed on the rubber base, 2 or 3mm apart, they conduct because the electroltye is on the rubber's surface.

I recently repaired a video monitor where a film of invisible electrolyte had coated the board in an area of a few square inches and corrupted the function of some high impedance circuits in a color processor circuit.The board also had a matt looking conformal coating which I think was microscopically porous. Standard pcb cleaner had no effect at all, in the end warm water managed to remove it. Another electrolytic nightmare.
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