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.
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
http://en.wikipedia.org/wiki/Capacitor_plague
or google "bloated capacitors" and you'll see lots of references to such...
Cheers
The ripple current/frequency that the capacitor has to filter also has direct effect on how much stress / gassing it does. Near the CPU - those would probably be the step-down supply filters - heavy current ripple, and pretty HF. I'd say that's the main cause, but undoubtedly there are effects from heat as well.
Cheers
Cheers
johndiy said:
True!
But in the case of failures on the motherboards - the caps that fail are usually rated at 6.3V or 10V, and they are used to filter the CPU supply - at that time was about 2V or so. Even Vio is only 3.3V. So that's half the rated capacitor voltage at most...
Cheers!
bikehorn - yeah how did that brown liquid get to the trannies without getting to the other places first???
The root cause of that sort of failure in all electrolytics (assuming they DID get the chemistry right!) is HEAT. It can be generated internally or externally, but usually, the catastrophic kind seen in the pic is generated internally. Either by overvoltage, wrong polarity, or, most commonly if it is a switching circuit, ripple current.
Just like in this day and age we get counterfeit transistors, it is not uncommon to get counterfeit electrolytics - usually a perfectly ordinary construction which has been branded as low ESR for switcher use, as the latter go for a rather higher price then the bog standard electrolytic cap. The result is what you see in the pic.
On occasion it boils down to a bad design, not bad caps per se. For instance, the cap failures on motherboards may not only happen due to using the cheapest caps or ones with a built in faulty chemistry, but also due to simply not having enough in parallel to cope with the ripple currents involved. Todays CPUs require high current low voltage supplies for the core and IO voltages, requiring ripple currents in their PSU caps that are easily on the order of 50-100A. The power regulators on a motherboard tend to be the most expensive part of the desing, and hence the one where savings are most likely to be made. Couple this to the fact that other hot components are likely to be very close by - transistors, diodes and inductors, and you get exploded caps. Something similar has happened in the pic above, as it seems to be a switching PSU for a car amp.
FInally, if the 'brown stuff' people are referring to in the pic is the brown stuff around the bank of transostors on the upper left, that is a Kapton insulator and not spilled electrolyte.
Just like in this day and age we get counterfeit transistors, it is not uncommon to get counterfeit electrolytics - usually a perfectly ordinary construction which has been branded as low ESR for switcher use, as the latter go for a rather higher price then the bog standard electrolytic cap. The result is what you see in the pic.
On occasion it boils down to a bad design, not bad caps per se. For instance, the cap failures on motherboards may not only happen due to using the cheapest caps or ones with a built in faulty chemistry, but also due to simply not having enough in parallel to cope with the ripple currents involved. Todays CPUs require high current low voltage supplies for the core and IO voltages, requiring ripple currents in their PSU caps that are easily on the order of 50-100A. The power regulators on a motherboard tend to be the most expensive part of the desing, and hence the one where savings are most likely to be made. Couple this to the fact that other hot components are likely to be very close by - transistors, diodes and inductors, and you get exploded caps. Something similar has happened in the pic above, as it seems to be a switching PSU for a car amp.
FInally, if the 'brown stuff' people are referring to in the pic is the brown stuff around the bank of transostors on the upper left, that is a Kapton insulator and not spilled electrolyte.
It's pretty exciting -- this is from the first photo-multiplier densitometer I worked on -- sounded like a shotgun blast.
fwiw -- in 1980's vintage SMPS many of the caps were enveloped in heatshrink tubing as failure was often the norm.
fwiw -- in 1980's vintage SMPS many of the caps were enveloped in heatshrink tubing as failure was often the norm.
An externally hosted image should be here but it was not working when we last tested it.
NASCAR Capacitors
I went to Michigan this summer in an RV to take in some NASCAR. We were running off the propane generator as we did not have a shore line. Noon Saturday, the RV filled with smoke and it looked like she was burning down. I thought the generator somehow caught on fire so everything was shut down and after the panic and the smoke subsided our neighbor helped me open a panel in the rear where the smoke came from. It was the inverter board for the power. Two very large filter caps had taken a beating, one vented and the other was ready to go.
I couldn't believe the poor engineering; the two caps were so close and almost touching the giant heat sink with all the semi's mounted to it. The board had lots of room perhaps 30cm x 30cm?
The RV was poorly designed too; the little metal cover vent was tucked in a tight corner down low and out of view. The girls just packed there luggage and clothes there blocking it. I guess we suffocated it.
It didn't take long to have a power cord over to our neighbors and it was pure debauchery until the end. We all had a good time!
Shawn.
I went to Michigan this summer in an RV to take in some NASCAR. We were running off the propane generator as we did not have a shore line. Noon Saturday, the RV filled with smoke and it looked like she was burning down. I thought the generator somehow caught on fire so everything was shut down and after the panic and the smoke subsided our neighbor helped me open a panel in the rear where the smoke came from. It was the inverter board for the power. Two very large filter caps had taken a beating, one vented and the other was ready to go.
I couldn't believe the poor engineering; the two caps were so close and almost touching the giant heat sink with all the semi's mounted to it. The board had lots of room perhaps 30cm x 30cm?
The RV was poorly designed too; the little metal cover vent was tucked in a tight corner down low and out of view. The girls just packed there luggage and clothes there blocking it. I guess we suffocated it.
It didn't take long to have a power cord over to our neighbors and it was pure debauchery until the end. We all had a good time!
Shawn.
Maybe some additional info could be found here:
http://www.badcaps.net/forum/
Apparently, there is some kind of plague.
Regards
http://www.badcaps.net/forum/
Apparently, there is some kind of plague.
Regards
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