What causes Rail Capacitors to Swell and Split Open? - diyAudio
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Old 17th September 2006, 10:54 PM   #1
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Default What causes Rail Capacitors to Swell and Split Open?

I have an amplifer and the Rail Voltage Capactors are Swelled big and one looks like it lots its juice. What causes this? The 12 volt supply caps look fine.
Also what cause the filter caps on the output of Class D amplifier to swell?
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Old 17th September 2006, 11:00 PM   #2
johndiy is offline johndiy  Greece
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overvoltage

john
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Old 17th September 2006, 11:05 PM   #3
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Oh, my. CHANGE ALL OF THEM RIGHT AWAY. They usually do that either when their voltage ratings are exceeded, or when they are connected with opposite polarity. If you don't change them, they will explode. Use higher rated caps as a replacement. If your output filter caps are swelling as well (I assume they're electrolytic), then there is probably something very wrong with the amp. Check it out, or if you don't have the skill, have someone check it out for you. Whatever you do, DON'T TURN IT ON.
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Old 17th September 2006, 11:13 PM   #4
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Quote:
Whatever you do, DON'T TURN IT ON.
Yup. That amp is in serious trouble. One or two caps could possibly be down to age, but all of them? Nah, that has been badly abused.
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Old 17th September 2006, 11:43 PM   #5
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Lightbulb AC Power???

A second possibility is that your bridge rectifier has failed, and/or some other means of AC power is being delivered to the filtering capacitors, at any rate, not good news!!! Change the bridge rectifiers, and capacitors right away, double check your voltage ratings on the caps.
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Old 17th September 2006, 11:53 PM   #6
kevinkr is offline kevinkr  United States
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Is this a car amplifier? Sure looks like one. Excessive battery voltage could be the culprit if the amplifier uses a switching power supply. Also age, heat, poor quality caps, and just running it too hard for very long time periods - subwoofer amps.
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Old 18th September 2006, 12:27 AM   #7
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I have repaired many of computer power units by changing exploded caps....on all lines 5 volt, 12 vols 3.3 volt....i never realy find out why they do that swell thing ??? and actual question that i ask myself is:
Are there special caps just 4 SMPS purposes or they R all the same ?
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Old 18th September 2006, 02:33 AM   #8
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Quote:
Originally posted by Dragance007
I have repaired many of computer power units by changing exploded caps....on all lines 5 volt, 12 vols 3.3 volt....i never realy find out why they do that swell thing ??? and actual question that i ask myself is:
Are there special caps just 4 SMPS purposes or they R all the same ?
Yes.There special caps for SMPSs.
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Old 18th September 2006, 02:55 AM   #9
clem_o is offline clem_o  Philippines
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Computer motherboards too have this problem. It's supposed to have been caused by a capacitor formula 'leaked out' to a competitor by a disgruntled employee. Apparently the formula was incomplete or not yet finished, causing the electrolytic to be unstable. The result is that capacitors produced using this electrolytic have a tendency to produce excessive internal gasses - failure can happen within low hundreds of hours of operation, versus the normal rated life of a few thousand hours. See this link

http://en.wikipedia.org/wiki/Capacitor_plague

or google "bloated capacitors" and you'll see lots of references to such...

Cheers
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Old 18th September 2006, 03:35 AM   #10
rdf is offline rdf  Canada
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Heat does that in a computer as well. I just tossed an ATX board with swollen caps adjacent to the CPU cooler. The same brand and value a centimeter away were fine.
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