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Capacitor lifespan

#85
MichelD said:
When I brought my Ampeg V4B in for an overhaul a few years ago, the tech re-tubed it but didn't touch the caps.
"Why not ?" I asked, "Guys on the Internet (this site) say you should replace the caps."

"You can't fix an amplifier over the Internet ," was the gruff reply.
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I agree with your tech.

That said, there is a lot of money to be made replacing perfectly good parts and even more money not replacing them and still charging for it (with exactly the same outcome)
 
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#88
mmon77 said:
Having worked with engineers though, I know that many of the so-called "poor design choices" came down to the one thing that is responsible for most bad ideas. Money. Most engineers, given the opportunity would design you a product that would never fail in a million years. The issue is that it would cost far too much. So things are redesigned with cheaper components with cost-savings in mind.

So blaming the engineers that designed it often isn't fair either.
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Having been an engineer in that very situation more than once, I couldn't agree more. The only saving grace for me is that most of what I worked on involved military aviation and/or weapons. In that world while money does narrow down choices occasionally, compromising in design to save a buck is often a very high risk/high consequence decision that many managers don't want any part of.
 
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#89
Al Kraft said:
Having been an engineer in that very situation more than once, I couldn't agree more. The only saving grace for me is that most of what I worked on involved military aviation and/or weapons. In that world while money does narrow down choices occasionally, compromising in design to save a buck is often a very high risk/high consequence decision that many managers don't want any part of.
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Rule number one... if lives are at risk, the cost is always a distant second after reliability.
 
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#93
agedhorse said:
If a bunch of caps care leaky, this indicates a more fundamental problem.

Electrolytic caps used for motor control (AC start and run caps) can degrade because of the type of construction, the ripple current and the environment (wide temperature and moisture) I wasn’t talking about this type of cap.

Why not start with basic troubleshooting first?
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Yes of course, it depends on the design and building of the electronic device.

It's not an electrolytic cap on motors, it's plastic caps on the comm bus between in and out unit.
Failing because of cheap solutions and design.


It's Basic troubleshooting for me to go thru this routine IF i don't know the exact issue.
 
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#94
agedhorse said:
I keep hearing the "all electrolytic capacitors" go bad preaching, the pundits stating that this varies from 10 years to 30 years yet in my experience on quality products 50+ years is a fairly easy metric to achieve. I have been accused of being ignorant, a dummy, and a moron because I don't agree with the mythology of old wive's tales.

I have provided some example calculations taking the data right off of capacitor data sheets and have arrived at calculated lifespans well in excess of 50 years, but these numbers simply aren't understood by the superstitious among us.

Here's the reliability numbers for a small power supply I was looking at, the mean time before failure is 3 million hours. There are several electrolytic caps in this power supply and 3 million hours is well beyond 200 years of continuous operation.

In general, probably 95% of all electrolytic caps replaced are perfectly good and will continue to be good for decades.

View attachment 5326378
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Before I read everything that follows your opening post, let me just say, as owner of a 1976 Ampeg SVT with all original caps, I am very happy to hear this.
 
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#95
Silky Johnson said:
Interesting info here, are there components that commonly fail while simply sitting in storage unplugged? I put a class d head away in a closet in my house that was functioning, then maybe 6-7 years later I pulled it out and it's just putting out a sort of electrical pulsing noise and I was afraid it was going to blow my cab so I shut it off right away. Even the power light was pulsing. I imagine that's not much to go on but any ideas?
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Let me guess...PF350?
 
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#98
agedhorse said:
In general, "reforming" applies to some early cap designs and also some specialty caps used in motor drives (that operate with high ripple currents) but in general I haven't seen the need nor have I seen any failures related to not doing it. But opinions being rear end orifices, everybody has one on this subject. The less educated and experienced, seemingly the more bizarre the opinion.



Beware that most of those opinions are from folks with virtually no education or real knowledge.

In my experience, far more damage is caused by the act of replacing the caps rather than leaving a perfectly good working amp alone. I see it fairly regularly.
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I agree that there is a large amount of unfounded opinion. After a while you can find enough info to compare and make a conclusion if it's good or bad and not because the same statement is made over and over.

It also depends on who is doing the replacing. "Working amp" can be subjective. When I bought the B15, it was working, sort of. Someone had been in there before me and left a few "treasures" to remove so I understand your statement.
 
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