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You will get opinions from electrolytics last forever to they need to be replaced every 10 years. The truth is they do wear out but the the variables are too great to make an accurate prediction of when. The 10 year people may be overly cautious, the 40+ year people are ignoring the facts, the truth is probably somewhere in the middle.
"Any" gear last longer if used? It may last much longer if used occasionally, especially if it gets hot or has moving parts or has tubes.
Bif,
Electrolytics form a thin layer of oxide on the aluminum and this layer gets thinner the longer they sit around with no voltage. If they sit too long and this layer gets too thin they can breakdown and be destroyed if you suddenly apply full voltage. That is why it is recommended to bring the voltage up slowly with a variac if you are turning something on that has been sitting around for a long time. This is called reforming the cap.
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Ralph, can you back that up with some references?
Curious where you got 1/2 fail in 20 years.
Even if true, given that the lifetime of a particular cap is inversely proportional to operating voltage and temperature I fail to see how this is useful for predicting the lifetime in any particular piece of equipment.
BTW that is not the definition of half life.
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. Marakanetz. capacitance could be OK but ESR and/or leakage too high. It is doubtful a 50 year old electrolytic is still in spec. Rrog, half life is the time it takes for something to decay or decline by 50%, it is not the time it takes for 50% of a group of objects to fail. For instance; the half life of a discharging capacitor is the length of time it takes for the charge to drop 50%. The half life of an ingested drug is the time it takes the body to eliminate half of it. http://en.wikipedia.org/wiki/Half-life. |
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I'm dumbfounded you would continue to defend what is clearly just plain wrong. You are evidently just making stuff up as you go along this time.
That is absolutely not the correct use of the term. It means something has half it's life left, not that half of a group are dead. Find one other example where it is used as you used it.
How could you possibly have seen it many times? Give me one example where you have seen a group of caps where 1/2 have failed after 20 years.
You'll have to do better than they teach it in technical school to have any credence. I taught in a technical school for ten years and I've never heard that 1/2 after 20 years statistic before. If it is correct you should be able to easily produce at least one credible source, but of course you can't because there are too many variables to have a statement like that be true.
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Plutonium is a good idea though, it has a half life of 80 million years ;>)
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. Here is another concern. My company has been dealing with this for several years now. The caps in the computers that run our equipment are failing at a very high rate. http://en.wikipedia.org/wiki/Capacitor_plagueI agree that MTBF is not applicable when talking about caps. It applies to complex equipment that needs to be repaired and put back into service. The time it takes a cap to fail is simply lifetime. Failing caps may lead to a lower MTBF for whatever they are installed in though. . |
. Ralph, Again, I'm dumbfounded you continue to defend what is clearly wrong. I've been dealing with electronics for over 30 years, taught it for 10, and have looked at this topic quite a bit since it often comes up on this and other forums. I've never seen it mentioned that 1/2 fail in 20 years or any other statistic that puts a lifetime like that on them. Any data always factors in temperature and voltage. I really respect most of what you say here but you clearly have no real data to back up any of these 20 year claims. Yes, English evolves but that doesn't mean it is acceptable to use it in any way you wish. Half life has a very clear, concise, scientific definition and your use of it is well outside that definition. Ir would be nice if someone on these forums would just once admit they are wrong. MTBF to describe cap failure is also incorrect as stated above. It refers to complex, repairable devices, not components. How can you possibly have a "mean time BETWEEN failures" for a device that is thrown away when it fails? There is never a second failure so there can never be a between. From this articleMTBF is properly used only for components that can be repaired and returned to service. Yes, I suspect the caps we are seeing fail are part of what you talked about. I posted a link to it in my response above. . |
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Minor, sounds like you are a very thorough tech.
Question: you say you check the caps for leakage and replace only as needed. What about a loss of capacitance and/or increased ESR? The amp may function with these problems but well below it's potential.
Also curious what method you use to measure the leakage.
Thanks
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No problem Ralph. I think it is a disservice to those who are trying to learn something here but If you are comfortable muddying the water with incorrect information then that is your choice. As one of the senior "experts" around here who comes from a technical background I would think you would strive for accuracy but your choice. I think from now on I'm going to refer to tubes as transistors since they transfer a signal and both words have trans in them. It's not correct but it's just as logical as your use of half life :>)
Like I said, it amazes me that nobody around here will ever admit they are wrong about something. When called on something they either don't respond, change their story, or do as you do and rationalize their incorrect responses. Actually, I find it a bit amusing.
In any case I'm done with it. Carry on.
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Rieff, we are systematically replacing all of the motherboards and video cards from the affected period.
Minor, so you mean physical leakage like stuff oozing out of them. The problem is they are performing below spec well before they start oozing. Since most don't have the equipment to test them some people recommend replacing after 10 years. I don't want to debate exactly how long is the right amount of time as that has been debated before but waiting until they ooze is a little too late.
take care
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Cathode, I don't feel it is being negative to correct a mistake. Electronics is a branch of physics. It is science. We use specific terms with specific meanings to avoid confusion. Why anyone would insist otherwise baffles me.
For example, your use of MTBF is simply incorrect. It is Mean Time BETWEEN Failures. It is not the same thing as MTTF.
Something is working.
It breaks down.
You fix it.
It works for some period of time. (this the "between")
It breaks again.
The mean of those "It works for some period of times" is the MTBF. It is not, as you stated, the length of time it takes for a certain percentage to fail.
That is not being negative. It is correcting a mistake.
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Minor I would have to disagree with "it is only too late if it fails" when it comes to audio. The statement may be true with power supplies for some equipment, but since they typically affect the sound of an amp long before they fail they have to be replaced sooner if your goal is optimal sound.
I do agree you should only replace caps in really old amps when necessary, but if we take 30 or more years to be really old then IMHO it is necessary in all of them. Bulging or oozing or not those caps have deteriorated. They need to go.
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Rower
What you say is just plain wrong.
Unless it is bulging or leaking fluid it is impossible to visually inspect a cap and determine if it has deteriorated. The capacitance drops and ESR goes up and they leak current and you have no way of knowing if or how much just by looking at it. You can delude yourself if you wish but all electrolytics slowly deteriorate in ways you cannot see.
All electrolytics have a limited lifetime. Take a minute to google the topic and you will get hundreds if not thousands of hits discussing this phenomenon.
It is impossible that your 30 year old caps function as well as new ones. To deny this is to deny that which has been studied extensively and is well documented. Your amp may sound "fine" whatever that means but that does not mean it wouldn't sound better with fresh caps.
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sorry................
your rant is just about impossible to follow
Sober up and then formulate a response.
Your position that power supply caps don't matter could not be further from the truth. They are the heart and soul of the amp. I build my amps and can assure you from experience that caps do affect the sound in a major way.
Taking one incidence (your old amps still work) to justify your stance makes as much sense as saying smoking is good for you because you know someone who is 95 and smokes a pack a day. There is a huge amount of data that says otherwise.
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. He's a little more specific than "LONG time." From the X150.5 manual.... Hardware Facts.. So how long will this hardware last? It is our experience that, barring abuse or the odd failure of a component, the first things to go will be the power supply capacitors, and from experience, they will last 15 to 20 years before needing replacement So you are at the lower limit of 15 years with a 1997 amp. Better start saving up for that cap change. If you agree with Pass then you must agree with my point above that caps 30+ years old should be replaced. . . |
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Rower,
Sorry, I just don't have the energy to read your dissertation. I glanced at it and despite your lengthy denial you are in a word
wrong.
Caps do matter.
Caps do have a profound effect on how an amp sounds
Caps do age and affect the sound.
No point in debating it further since you clearly dont want to be bothered with the facts.
Believe what you want but if you would bother to do a little research you would find an overwhelming body of evidence from hobbyist as well as manufacturers of amps including the maker of your Pass and those who make caps.
Take care
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Once again, I don't have the energy to read through your dissertation.
Despite whatever you said it is well documented that caps do age and I've replaced enough of them to know they do have a profound effect when I do.
If you google "electrolytic capacitor aging" you will find a ton of information that contradicts your position including Nelson Pass who's equipment you list in your system.
I will not be responding further since you clearly have no intention of accepting the overwhelming body of evidence that contradicts what you say. Believe whatever you wish. It is certainly cheaper than properly maintaining your equipment.
Take care
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How would you know if your self described "low end" systems have deteriorated when they don't sound that good in the first place.
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Oh my, you are quite the clever one aren't you? I'm so glad we have such a quick witted forum policeman on board.
attack?
putrid?
rants?
denigating? (the correct word is denigrating. If you want to impress us with your vocabulary you should check your spelling)
Hold on a second, your idea that using low-fi, antiquated equipment to prove caps don't deteriorate is rightly, politely refuted and you consider this an attack? There is no "mine is better than yours attitude" in that. It is a simple statement of fact.
Your rants full of insults and abuse is much more denigrating than what you rant about. Probably one of the most ironic posts I've ever seen here.
Thanks for entertaining us.
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