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Old 04-28-2022, 09:54 AM   #1
Crystaleyes
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Default Is an exploded cap still usable?

I just bought two non-working Kenwood CS4035 scopes to muck around with, as I'm in the process of learning electronic repair, so figured they should teach me something.


They have linear power supplies, and on one of the PSU boards, there is a 4700F electrolytic which had it top blown open.
Turns out that both scopes have had various repair/mods done before and this cap had been fitted in reversed polarity.

Anyway, out of interest, I figured I would see how a blown cap tested, so flattened the top and took a reading, which came back as 4800F, with negligible ESR and V loss.

I was not expecting a reading anything like that, and it has never even entered my head that an exploded cap might still be usable

So my question is, could this capacitor still be used?

Last edited by Crystaleyes; 04-28-2022 at 10:06 AM..
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Old 04-28-2022, 11:00 AM   #2
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Default Re: Is an exploded cap still usable?

Quote:
Originally Posted by Crystaleyes View Post
So my question is, could this capacitor still be used?
No, at least not for any extended time period, if it was relatively new and just reversed polarity there may still be electrolyte in it now leading it to test "good" but now that the seal is broken (even if you pushed the vent back down it isn't sealed anymore, that is a solid piece of metal from the factory with relief notches stamped into it to allow for venting if the can is over pressurized, once it vents that seal is broken) it will likely dry out and go "bad" in short order (I guess you could theoretically epoxy the vent, but then if it ever needs to vent again it will go "kaboom" and possibly do allot more damage).
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Old 04-28-2022, 11:25 AM   #3
Crystaleyes
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Default Re: Is an exploded cap still usable?

Thank you.

It would have been changed regardless, however I was just surprised to get that reading.

Every day's a school day...
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Old 04-28-2022, 12:29 PM   #4
Per Hansson
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Default Re: Is an exploded cap still usable?

Maybe you will find this thread a fun read
https://www.badcaps.net/forum/showthread.php?t=102937
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