all the electrolytics in the power section I replace every 5 years. the rest of them are subjective. if you like the sound I would leave them alone. when you start changing caps in the signal path sometimes the sound of the amp will change.
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Capacitor life and death
- Thread starter Jammin Johneboy
- Start date
- Feb 12, 2006
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- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
I tend to agree with Eight_stringer on this.
To answer his question about how signal gets across a cap, the mechanism is electric field via transfer of charge.
Most quality film and ceramic caps should last between 25-50 years or more. There's not much to fail.
Most quality electrolytics used appropriately, and sized appropriately should remain in spec for between 20-40 years. Where problems crop up is in cases of junk parts and poor application.
On pcb applications, there are only so many times you can replace a part before ending up with other problems.
To answer his question about how signal gets across a cap, the mechanism is electric field via transfer of charge.
Most quality film and ceramic caps should last between 25-50 years or more. There's not much to fail.
Most quality electrolytics used appropriately, and sized appropriately should remain in spec for between 20-40 years. Where problems crop up is in cases of junk parts and poor application.
On pcb applications, there are only so many times you can replace a part before ending up with other problems.
- May 9, 2008
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- Proprietor Springvale Studios
A word in support of much maligned paper in oil caps, quality PIO's like "vitamin Q" and "Zenith" are not subject to the same kind of drying out as electrolytic types and do last a very very long time.
When used in the signal path, they are responsible for imparting a specific tone and changing them out for metalized poly types can make an amp sound rather too bright.
I change electrolytic's after about 15 years automatically but I never change other types unless they fail.
When used in the signal path, they are responsible for imparting a specific tone and changing them out for metalized poly types can make an amp sound rather too bright.
I change electrolytic's after about 15 years automatically but I never change other types unless they fail.
I think that due to Internet and all this capacitor -thing has been blown out of proportions.
Yes, it is an undeniable fact that electrolytic caps do have a service and shelf life. However, the practical lifetime depends on overall construction of the capacitor and the operating conditions; one surely will die faster when operating under higher temperature and ripple currents. I've seen the "15 - 20 years" -figure for overall estimation quoted for few decades so I have strong doubt that the figure might no longer apply to modern components, and keep in mind, we have examples of entirely new capacitors that for some reason failed within the first year of their service life.
At best it's an estimation. ....with tolerance of +/- 30 years...
I sure can't generate any kind of statistic. From the various stuff I fixed only few old amp had issues with aged capacitors, and issues with age-induced corrosion, wear, intermittency and component value drift seemed to be far more popular than issues with aged caps. I'd put aged capacitors far down in the list of usual causes for amp issues. Never had any issues with old caps exploding or simply working inadequately without "reforming" them (et cetera) either.
It's pretty telling that we only need to look at this thread and we already have folks blaming old caps for the hum that is actually produced by their pickups, or we have comments about value drifts in other ordinary components too, not just electrolytic caps. As said: blown out of proportions.
Yes, the issue is real but generally I would only worry about it when it indeed becomes an issue. It might take only a year, or it might take fifty years. There is no universal rule of how fast a cpacitor fails due to its age as far as I know.
Yes, it is an undeniable fact that electrolytic caps do have a service and shelf life. However, the practical lifetime depends on overall construction of the capacitor and the operating conditions; one surely will die faster when operating under higher temperature and ripple currents. I've seen the "15 - 20 years" -figure for overall estimation quoted for few decades so I have strong doubt that the figure might no longer apply to modern components, and keep in mind, we have examples of entirely new capacitors that for some reason failed within the first year of their service life.
At best it's an estimation. ....with tolerance of +/- 30 years...
I sure can't generate any kind of statistic. From the various stuff I fixed only few old amp had issues with aged capacitors, and issues with age-induced corrosion, wear, intermittency and component value drift seemed to be far more popular than issues with aged caps. I'd put aged capacitors far down in the list of usual causes for amp issues. Never had any issues with old caps exploding or simply working inadequately without "reforming" them (et cetera) either.
It's pretty telling that we only need to look at this thread and we already have folks blaming old caps for the hum that is actually produced by their pickups, or we have comments about value drifts in other ordinary components too, not just electrolytic caps. As said: blown out of proportions.
Yes, the issue is real but generally I would only worry about it when it indeed becomes an issue. It might take only a year, or it might take fifty years. There is no universal rule of how fast a cpacitor fails due to its age as far as I know.
Temperature, storage, operating conditions, as well as design, play a roll with life expectancy of electrolytic caps.
I find that the worst offenders are the original Mallory FP type can caps. Many amps use them. Some designs stress them more than others. Sometimes when an amp is sitting a long time, the rubber safety vent seals degrade and the caps dry up. After reconditioning, some caps initially test good but will degrade quickly.
I have two Hammond organs that date back to 1936 with all the original caps and they work just fine. Sometimes I see the wax covered paper caps not holding up. Leslie Mallory ecaps often need attention. With old HP and Tektronix test equipment, the ecaps seem to last a long time. But at the same time I see a lot of musical instrument amps with bad electrolytic caps. A thirty year old amp is going to have issues. A twenty year old amp could very will develop issues if put into service. Other times ecaps simply develop a problem and need to be replaced.
Sometimes caps are changed as a matter of preventative maintenance. I've seen schedules where the ecaps are changed every five years for example. A heavily used gigging amp needs to be kept up to spec and reliable. People in the industry will change the electrolytic caps and tubes as per a maintenance schedule rather than wait for something to break. Same goes for recording studios and other commercial applications where they have maintenance schedules in place so that they can schedule the availability of equipment.
I find that the worst offenders are the original Mallory FP type can caps. Many amps use them. Some designs stress them more than others. Sometimes when an amp is sitting a long time, the rubber safety vent seals degrade and the caps dry up. After reconditioning, some caps initially test good but will degrade quickly.
I have two Hammond organs that date back to 1936 with all the original caps and they work just fine. Sometimes I see the wax covered paper caps not holding up. Leslie Mallory ecaps often need attention. With old HP and Tektronix test equipment, the ecaps seem to last a long time. But at the same time I see a lot of musical instrument amps with bad electrolytic caps. A thirty year old amp is going to have issues. A twenty year old amp could very will develop issues if put into service. Other times ecaps simply develop a problem and need to be replaced.
Sometimes caps are changed as a matter of preventative maintenance. I've seen schedules where the ecaps are changed every five years for example. A heavily used gigging amp needs to be kept up to spec and reliable. People in the industry will change the electrolytic caps and tubes as per a maintenance schedule rather than wait for something to break. Same goes for recording studios and other commercial applications where they have maintenance schedules in place so that they can schedule the availability of equipment.
- Feb 12, 2006
- 60,949
- 5
- 220,576
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
Modern quality electrolyric caps these days, with proper undrstanding of their applications, results in very long lives.
I just retired my primary FOH console last week, a 20 year old Yamaha PM series. It has all original caps (including both power supplies) and it still meets ALL factory specs, even the 20Hz spec that folks seem to be sure is impossible (if youlisten to all the BS on the internet). Recapping this console is a significant job, there are close to 600 caps that would need to be replaced. If there was a real reasonto do so I wouldn't hesitate (it's a trivial job as my shop used to do frame up comsole rebuilds) but when there is no reason to do so, why should I waste the time and money to do this? I don't have the need to "feel better" about myself for fixing a non-problem. This console has done more A circuit shows successfully (right to the very end) than those folks suggesting that the caps are all worn out and "must" be replaced have ever done. Sheeh
I just retired my primary FOH console last week, a 20 year old Yamaha PM series. It has all original caps (including both power supplies) and it still meets ALL factory specs, even the 20Hz spec that folks seem to be sure is impossible (if youlisten to all the BS on the internet). Recapping this console is a significant job, there are close to 600 caps that would need to be replaced. If there was a real reasonto do so I wouldn't hesitate (it's a trivial job as my shop used to do frame up comsole rebuilds) but when there is no reason to do so, why should I waste the time and money to do this? I don't have the need to "feel better" about myself for fixing a non-problem. This console has done more A circuit shows successfully (right to the very end) than those folks suggesting that the caps are all worn out and "must" be replaced have ever done. Sheeh
Yes absolutely, they keep getting better. The Panasonic industrial snap-in caps that I use typically have a 3000 hour service life at 105 degrees C, much longer at lower operating temperatures. That's why I use them when I can. A lot better than the products that you see in vintage musical instrument amps.
I certainly wouldn't recommend replacing 600 caps in a console. I've rebuilt studio analog consoles and outboard equipment and appreciate the work that it involved in such a folly. Clients want the old classic sound with some improvements such as a lower noise floor. They run these things long hours, some are never shut off except for maintenance. Power supply electrolytic caps are often changed. Electrolytic caps and some film caps are changed on modules. Sometimes they want new wire, patch bays or other things configured, cleaning, that sort of thing. Never wholesale recapping. I've owned Studiomaster, Yamaha, and Fostex consoles for live work. They stood up well for many years. The Fostex has a bit of hiss but that isn't from the power supply. It performs to specs, the specs just aren't that good. I use a Mackie Onyx console now because of the high speed digital interface. But a console recap is a far cry from a few caps in an amp.
Earlier I was pointing out that there's a difference between a professional application where they want preventative measures taken to keep equipment in service vs someone that wants an amp checked out. I was also very clear to specify electrolytic caps in my comments and that didn't include coupling or other caps. I really hate to see someone go into a piece of equipment and blindly change out all the caps. This can change the character of the sound.
