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Capacitors: Who is Right? What ages them faster?

Power supply electrolytics - the main thing audiophiles worry about getting old and having to replace.

What's the truth here?

Manufacturers can be quoted as saying the life expectancy of caps is anywhere from 10 - 15 years. Is this true? Why is it that Krell amps seem to need capacitor changes in 8 years, while people have receivers from the 70's that never had caps replaced?

Another controversy, with three viewpoints:

(1) I was told that caps age faster in amps that are left on continuously. The rationale here is that the lack of a discharge cycle is not good for the caps since they are in a constantly charged state.

(2) Others claim that leaving a unit unused in a box for years also shortens the life of the caps, as they never see a charge.

(3) Others say the lifespan is the same whether on the shelf, or in the unit.

Who has the technical background or the knowledge to sort this out?
kevziek

Showing 3 responses by kevziek

kevziek OP
323 posts
 
Arthur,
I spoke to Nelson Pass today. He said that, over time, the fluid in the cap slowly dissipates from the cap, until it eventually dries out. He believes that if the amp is left on, the higher ambient temperature is accelerating the process, but by how much, he didn't seem sure.

Your colleague is probably more knowledgeable than Pass is on this issue, since this is his profession. I'll be very interested in his answers......
kevziek OP
323 posts
 
Sean: I don't know if you are correct about the caps being exposed to high heat. Nelson said that he has always run the caps considerably below the rated temps. He mentioned 55 degrees C, while ratings are 85 C. The heat sinks may be absorbing the bulk of the heat, while the internal components remain cooler. I'm not sure on this, though.
kevziek OP
323 posts
 
Sean, in my conversation with Nelson, he indicated that the caps would probably dry out faster when the amp is on all the time, probably due to the heat, as you suggest. Yet, he seemed to feel that you shouldn't worry about life span for probably 15 years, in his designs, anyway. How much of this is conjecture on his part, I don't know. That's why I eagerly await Aball's buddy's opinion.
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