Capacitor types

amirm

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Apr 2, 2010
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Audiophile products often tout the capacitor types they use. Here is a nice video from Dave Jones on different caps and issues with some types:

 

amirm

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Apr 2, 2010
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Seattle, WA
As a related item to the video, and poor life of electrolytic caps, here is a quick story. I was in my den where I have my audio workstation organizing my files and I kept smelling this foul odor. It smelled like a dead animal! I kid you not. So I thought maybe an animal had made it in there and died. I search and search and I cannot find the source. Right then I start to hear a relay clicking erratically and one of the channels on my Mark Levinson DAC cutting out. I think that is a strange coincidence. I pop the top off and this is what I see:



Notice the puddle of oil like substance around that vertical capacitor. I get my noise to it and that is what I was smelling!!! In all the years of repairing electronics I had never seen a device have such odor. Anyway, pulled that cap out and tested it. Its value showed half as much and bottom of it had leaked out the fluid. I replace the cap, power the unit and smoke pours out of a nearby power resistor. I see that it drives the blue capacitor in the picture above. I pull that out and test it and it shows the right value. Since I had it out, I replace it anyway and boom, the DAC works and problem resolved. The cap did not show signs of damage but clearly it was.

The DAC is about 12-13 years old. Ironically I had thought a few months ago that I should replace all the caps in it as this is around the time caps dry out and fail. But of course I did not get around to it.

Failure mode is obvious for the first cap. Right next to it is a "line driver" IC which looks like a power transistor with that metal tab. It gets quite warm and heats up the cap next to it, causing it to fail sooner. ML had picked 105 degree C rated cap instead of 85 which is a good move but still, it would have taken very little work to distance the two parts. It is amazing how this little bit about how to keep caps cool is not known even by best engineers. I think they should be forced to repair electronics for a while in order to know what fails :). I bent the line driver forward just a fraction of an inch on both channels and the impact on cap temp was huge. It no longer heated it.
 

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amirm

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Apr 2, 2010
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Seattle, WA
Thanks! I wish I had known about that when I was trying to insulate a wire in my boat engine! Had to special order it from the auto parts store.
 

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