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
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
This datasheet of Panasonic FM does show correlation between bigger capacitance and lifetime.
http://www.farnell.com/datasheets/26036.pdf
http://www.farnell.com/datasheets/26036.pdf
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.
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.
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.
Since the topic has shifted to temperature somehow, while at it may I ask...
The temperature theory, does it apply for 85 vs 105 degree rated capacitors ? i.e. 105 degree capacitors last 100x longer compared to 85 degree capacitors at say 60 degrees.
Of course, I know in reality the lifetime is affected more by other things than temperature rating, but would be interesting to ask.
The temperature theory, does it apply for 85 vs 105 degree rated capacitors ? i.e. 105 degree capacitors last 100x longer compared to 85 degree capacitors at say 60 degrees.
Of course, I know in reality the lifetime is affected more by other things than temperature rating, but would be interesting to ask.
One might think that, and I have too
But maybe it just means they are tested to endure and survive tougher conditions
They are tested and specced to do that
But it doesnt mean that the lesser 85degree doesnt survive the same, its just not been tested to do that
Might even be the exact same cap, just with a different label
To be realistic, 4000hours is like nothing, other than it means the test cap has survived exstreme heat conditions
I dont know, but if the heatsinks are 50degree, maybe the air inside the box is no more than 40degree
And who knows how amps are in 10years
Anyway, the real cap killer seems to be instability, oscillation can boil a cap
Please dont ask me why
I dont know why, but I always get suspicious whenever I see fancy black and gold labels
Why we fall for that is beyond me, but we do
Im no better, cause I think the ordinary looking Panasonic with black and white looks boring, but they are probably just as good as any
Now, the true quality is to me blue, and blue probably because it comes from the old days when Spraque was the ultimate cap, and being blue
Funny ehh, quality being about colours
But maybe it just means they are tested to endure and survive tougher conditions
They are tested and specced to do that
But it doesnt mean that the lesser 85degree doesnt survive the same, its just not been tested to do that
Might even be the exact same cap, just with a different label
To be realistic, 4000hours is like nothing, other than it means the test cap has survived exstreme heat conditions
I dont know, but if the heatsinks are 50degree, maybe the air inside the box is no more than 40degree
And who knows how amps are in 10years
Anyway, the real cap killer seems to be instability, oscillation can boil a cap
Please dont ask me why
I dont know why, but I always get suspicious whenever I see fancy black and gold labels
Why we fall for that is beyond me, but we do
Im no better, cause I think the ordinary looking Panasonic with black and white looks boring, but they are probably just as good as any
Now, the true quality is to me blue, and blue probably because it comes from the old days when Spraque was the ultimate cap, and being blue
Funny ehh, quality being about colours
I would expect so. Less room for the conductive parts (more foil / electrolyte). Check the datasheet.
FYI, I haven't seen a single snap-in that was "slow". Firing a random 220uF 400V into a xenon flash tube, I got a discharge two times faster than any film capacitors I tried (e.g., motor run). Typical discharge for a motor run cap, 20-30us. The snap-in did it in 10. General purpose electrolytics, on the other hand, can be painfully slow: a 100uF 350V axial took miliseconds to discharge, equivalent to 2-3 ohms ESR -- which is as the datasheet states. YMMV, especially for low voltages.
Note that none of this actually matters for most audio purposes. Indeed, I can think of situations where low ESR might make an amplifier unstable. I've also seen switching supplies go unstable when too little ESR is used (for instance, the ESR might be part of the control loop, so it effectively provides derivative feedback, stabilizing the circuit). A proper circuit is engineered on all levels, including capacitor selection; don't just grab something that looks good (or advertizes anything about "sonic quality", which should be a big red flag that something ain't right here), use the component appropriate for its circuit.
Tim
FYI, I haven't seen a single snap-in that was "slow". Firing a random 220uF 400V into a xenon flash tube, I got a discharge two times faster than any film capacitors I tried (e.g., motor run). Typical discharge for a motor run cap, 20-30us. The snap-in did it in 10. General purpose electrolytics, on the other hand, can be painfully slow: a 100uF 350V axial took miliseconds to discharge, equivalent to 2-3 ohms ESR -- which is as the datasheet states. YMMV, especially for low voltages.
Note that none of this actually matters for most audio purposes. Indeed, I can think of situations where low ESR might make an amplifier unstable. I've also seen switching supplies go unstable when too little ESR is used (for instance, the ESR might be part of the control loop, so it effectively provides derivative feedback, stabilizing the circuit). A proper circuit is engineered on all levels, including capacitor selection; don't just grab something that looks good (or advertizes anything about "sonic quality", which should be a big red flag that something ain't right here), use the component appropriate for its circuit.
Tim
yes
and according to Panasonic 'test manual' the specced temperature ratings means that its been exposed to that excact temperature, for a short period
after that it will last the specced life time at the much lower 20 degree
so I think there is wide misunderstanding of what specced life time really means
and according to Panasonic 'test manual' the specced temperature ratings means that its been exposed to that excact temperature, for a short period
after that it will last the specced life time at the much lower 20 degree
so I think there is wide misunderstanding of what specced life time really means
Old thread.... but anyway.
So here is my question.
If an electrolytic is rated for 4000 hours at 85 degrees. And then it sits unused for 5 years at around 20 degrees, is it still good to use?
I think it is OK to use, but I wonder how long it's life would be when voltage is applied and it sits next to a voltage regulator, and the cap gets to perhaps 40 degrees?
Next scenario is that the cap sits unused for 10 years?
Is it still good?
Now, I have no intention of purchasing these, but, what about those new old stock black gate capacitors that people advertse on ebay or other online parts shops?
They are quite old now. Are people who buy these spending money on shrivelled up old prune capacitors? Or are they still good?
So here is my question.
If an electrolytic is rated for 4000 hours at 85 degrees. And then it sits unused for 5 years at around 20 degrees, is it still good to use?
I think it is OK to use, but I wonder how long it's life would be when voltage is applied and it sits next to a voltage regulator, and the cap gets to perhaps 40 degrees?
Next scenario is that the cap sits unused for 10 years?
Is it still good?
Now, I have no intention of purchasing these, but, what about those new old stock black gate capacitors that people advertse on ebay or other online parts shops?
They are quite old now. Are people who buy these spending money on shrivelled up old prune capacitors? Or are they still good?
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