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Old 14th December 2010, 07:08 PM   #1
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Default caps and lifespan

Hey

this is my first post here. im rather new to electronics so i guess this is a newbie thread. im about to order capacitors in order to recap my mixing desk. its a very nice all discrete desk, so i want to get high quality caps. i did some research and it seams to come down to either nichicon kz, elna Silmic or panasonic fm. now my big question is lifespan. the panasonic last a lot longer telling from the datasheet. the nichicons and elnas only last 1000 hours...what does this mean in real life?
my desk is running all day...everyday. does this mean the nichicons and elnas will go bad after a little over a year? i must be getting something wrong....the caps that are in there now are at least 15 years old...still working. id appreciate if someone could give me some advice. thanks a lot.
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Old 14th December 2010, 10:15 PM   #2
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Default predicted capacitor life

Nichicon, for example, sells both 1000 hour and 5000 hour caps in the 470 uf 50 V size. Newark.com has both. The 1000 hour is $.91, the 5000 hour is $1.84.Here is the 5000 hour link http://www.newark.com/nichicon/upm1h...ial/dp/65R3633 . As I am not selling into a competitive market where first cost is king, I tend to buy 2000 hour up electrolytic capacitors so I don't have to replace it again next year. I don't run competitive trials, and I don't know of a consumer digest of electronics parts. I do know I bought a competitively priced HDTV converter from a big box retailer, and the caps were bad the day I bought it. It has diagonal lines (60 hz) in the signal that go away after 10 minutes. I would guess the 5000 hour cap has more expensive materials or better final assembly testing than the competing cap from the same manufacturer. I like newark because they highlight the hours life right in the selector table, so you can filter out the garbage without wasting time. In europe they are farnell.co.uk.
Some posters on this board are married to some series of cap like it was a religion or something. I'm more into numbers. ESR can be important,self inductance and life can be important, copper leads instead of steel can be important to reduce frequency cold joints hand soldering. You have found a Nichicon "competitive" series, apparently. Nichicon also has caps installed in Siemens premium brand 460 V 3 phase motor drives, where temperature is extreme and customers buy enough ot the same device to remember if they are changing it out more than average. The nichicons are not a big cause of failures there, but I would suspect they are not the cheap ones. I've seen a couple of nichicons blown up after 15 years high temp 5 days a week 24 hours/ day service. So the brand is not as important as the series the buyer chooses. I've got both blown up Siemens motor drives, and Semi drives. The Semi brand drives tended to leak slime into their enclosures at about 4-5 years, then refuse to power up on a cold morning. I spent a lot of Sunday nights rewiring machines that had Semi drives for something else, because Semi drive was bankrupt. Siemens drives do not have the 5 year leaky caps problem. Semi drives did not use nichicon.
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Last edited by indianajo; 14th December 2010 at 10:37 PM.
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Old 14th December 2010, 10:43 PM   #3
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Those lifetime figures can be confusing. Usually they are the guaranteed life at the maximum operating temperature, 85C or 105C. At more normal temperatures (i.e., in well ventillated and well designed equipment, rather than cheap far-east plastic stuff) they will be at little more than room temperatue all their life and will last considerably longer.

5000h life also doesn't mean they will die at hour 5001; it does mean that they are no longer expected to be within their rated tolerance (+10% / -5% or whatever it is). Your old caps are still working but they may have dropped in value to say 50% or 60% of their correct value. In good designs, they are way over-rated so the anticipated change in value is accounted for and shows few problems.
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Last edited by Steerpike; 14th December 2010 at 10:46 PM.
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Old 15th December 2010, 12:02 AM   #4
jcx is offline jcx  United States
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Default buy a high temp rated cap and keep it cool

http://www.niccomp.com/Products/Gene...lifeexpect.pdf

and buying larger V rating helps a little on life too

any signal coupling electros should be Al, non/bi-polar, with high V overating factor - even if they have bias V - see Bateman's "Capacitor Sound" results - the old "back-to-back" polar configuration didn't give as low measured distortion as non/bi-polars with full thickness oxide grown on both foils

also technology evolution allows more C in the same case size - another plus for signal coupling distortion minimization

of course even the worst film was better than the best electrolytic

Last edited by jcx; 15th December 2010 at 12:10 AM.
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Old 15th December 2010, 12:20 AM   #5
kevinkr is offline kevinkr  United States
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The biggest bang for the buck lifetime wise is to buy caps rated for 105 degree C.

Note that for every 10 C reduction in internal temperature the capacitor life doubles. In cases where there is no ripple current this is the prevailing ambient temperature around the cap. In the case where ripple current is present the internal temperature may be appreciably higher than ambient. It pays to look for low ESR types with the highest ripple current ratings you can find for these applications. (Input filters in linear supplies for example.)
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