Electrolytic cap hooked up in reverse. Did I kill it? - diyAudio
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Old 28th September 2005, 06:02 PM   #1
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Default Electrolytic cap hooked up in reverse. Did I kill it?

Last night when testing a power supply, I accidentally ran 35v reversed through a bank of 50v aluminum electrolytics. Each rail has five 10,000uf caps and a 4,700uf cap with a 1ohm resistor in series between them (a la http://www.diyaudio.com/forums/attac...amp=1124231976 )

I found out after I had the bridge rectifiers reversed, but not before I had turned the circuit for 4-5 seconds a few times while debugging. When I turned it on, I heard a crackling sound from the PSU and the 4,700uf caps were hot to touch (the 10,000uf were not). I will be fixing the board and retesting the caps tonight, but I want to ask, from people's experiences:
are the caps probably dead?
if not, could their performance/values be affected?
How can I test if they have been damaged or will have an adverse affect on the PSU's performance? (ie, reduced capacitance/ripple current)
Should I just toss the two 4,700uf caps that got hot and order replacements (I don't want to wait for new ones)

Note: They are Panasonic TS-UP caps

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Old 28th September 2005, 06:46 PM   #2
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I did the same with some nichicon 10.000uf caps some time ago, and they were useless afterwards.

and again i did the same with some simens 100uf caps, but they just got luke warm, so i asked the same question on the forum, and the general perception of the people who answerd me said they might work NOW, but their lifespan had been drastically shortened and internal shorts were a very real possibility.

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Old 28th September 2005, 08:54 PM   #3
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Judging by the schematic, would you guess all are messed up? or just the 4,700uf cap that got hot?
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Old 1st October 2005, 05:58 AM   #4
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If you have a way to test the 10.000uF caps, I think you will find that they are not 10.000uF any more.......
I have also tried it once, and most of the caps where only 1/10 of the original value afterwards
Free Schematic and Service Manual downloads www.audio-circuit.dk, Spare time company (just for fun): www.dupont-audio.com
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