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Old 26th March 2010, 10:28 PM   #1
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Default Do larger caps age better then small ones?

when re-capping a vintage amp do you always need to replace the large filter caps? I see places sell large caps as NOS, does this mean they age better then smaller value caps?
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Old 26th March 2010, 10:55 PM   #2
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What do you mean by large?

The larger capacitors in amps are generally electrolytics, which have poorer lives than other (smaller) types due to the loss of electrolytic over time.

When re-capping an amp, you need to replace those caps which are out of spec. Determining which these are is another matter. Typically people replace all the electrolytics as a precautionary measure and hopefully to extend the future life of the amp before it needs attention again. The other caps will be left unchanged unless there is a particular reason to think there is need.

Electrolytics can deteriorate in storage as in use. NOS generally implies a period of storage.

w
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Old 26th March 2010, 10:58 PM   #3
a.wayne is offline a.wayne  United States
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NOS ... What is NOS ?
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Old 26th March 2010, 11:02 PM   #4
Apex Jr is offline Apex Jr  United States
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NOS = New Old Stock

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Old 26th March 2010, 11:30 PM   #5
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by large caps I mean the big filter caps on the power supply. large capacitance.
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Old 27th March 2010, 02:35 AM   #6
wwenze is offline wwenze  Singapore
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This datasheet of Panasonic FM does show correlation between bigger capacitance and lifetime.

http://www.farnell.com/datasheets/26036.pdf
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Old 27th March 2010, 06:47 AM   #7
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Quote:
Originally Posted by wwenze View Post
This datasheet of Panasonic FM does show correlation between bigger capacitance and lifetime.

http://www.farnell.com/datasheets/26036.pdf
Thanks for that link
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Old 31st March 2010, 11:11 PM   #8
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Default big cap life

All the photos of cap explosions I have seen on the internet (i haven't seen every one obviously) was a pretty big filter cap for a power supply unit. I blew a little one on a battery charger trans by putting it in backwards, it hissed and bubbled but did not throw conductive borax water all over everything the way a big one can. Some of the Mallory 10 15 and 20 uf units In my 1968 organ and 1970 tube tester seem to be doing fine, (the harp circuit on the H100 works okay, replacing all 110 of them would cost $160) whereas replacing the can filter caps (about 800 uf total at 350-450 volts) raised the volume by about 30 db and restored function to the "percussion" circuit which was dead powered by 1968 can caps. The above chassis can caps replaced were Sprague cans, mostly. Eveybody that has thought about buying an unrestored H100 has complained about the low volume, whereas mine with new caps will rattle the sheet music and the windows.
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Old 1st April 2010, 02:47 AM   #9
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Anything electrolytic over 30 years of age is to be replaced, or else it's your own risk!

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Old 1st April 2010, 03:15 AM   #10
poptart is offline poptart  Canada
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You guys all probably know this, but for the record temperature is by far the most significant factor aging an electrolytic cap. Sprague used to have some good pages showing this kind of stuff. All the other variables are completely swamped by that one. Interesting (to me) that DC voltage up to the working voltage is pretty insignificant too, which is good info for people looking to build a bulletproof amp, don't bother getting caps overated for voltage, moving them another inch from the closest resistor or heat source will have a much better effect.
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