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Topic: Capacitors Lifespan (Read 9347 times) previous topic - next topic
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Capacitors Lifespan

Hello,

Does anyone know the general lifespan of electrolytic capacitors in a power amp?

I have a (rated 200W per channel 8 ohm load) power amp that is 19 years old. Some of those 19 years have been spent sitting in storage boxed up, the rest of the time it was in regular use.

I purchased the amp new and the amp has been 'babied' all of its life by driving efficient 8-ohm speakers and was not ever pushed to its limits.

A visual inspection of the caps inside showed nothing obvious, leaking, bulging, etc. I am not a technician so my quick inspection was not thorough.

I read somewhere that a caps life in a power amp is 15 years max.
Ad hominem attacks are not Science.

Capacitors Lifespan

Reply #1 –
I've actually been wondering about this as well. I'm using an old Technics amp from the 70s and a pair of JBL speakers also from the 70s. Everything looks works and sounds just fine, so if there is any audible change due to capacitor aging, it must be very subtle.

Capacitors Lifespan

Reply #2 –
When they finally start going bad you'll notice problems with the sound, you might not have problems for the first hour until things warm up.  Well there's all kinds of electrical problems that can occur, heck it might even turn on or start shutting off under stress.  It's not subtle when they go bad and start causing the electronic device to malfunction or exhibit major changes in performance.  If you're concerned about your device's capacitors check them with a multimeter (with extreme caution so you don't get killed), if you feel the visual inspection wasn't enough.

Electronics can sometimes last a very long time before they fail, if they're built really well.

Capacitors Lifespan

Reply #3 –
It really depends on the quality of the parts and how the circuit was built; lifespan varies many times over with temperature, part quality, and ripple current.

Capacitors Lifespan

Reply #4 –
I have a Bass amp which is 37 years old and the caps are still fine. It's hard to nail down a "lifespan" for this stuff as some may last only months while others last a century Your best bet is just run it and see if it holds up to use. If it does I'd probably consider it more reliable than a new amp that hasn't proven itself.

Capacitors Lifespan

Reply #5 –
Quote from: NaturalTimbre on
Hello,

Does anyone know the general lifespan of electrolytic capacitors in a power amp?

I have a (rated 200W per channel 8 ohm load) power amp that is 19 years old. Some of those 19 years have been spent sitting in storage boxed up, the rest of the time it was in regular use.

I purchased the amp new and the amp has been 'babied' all of its life by driving efficient 8-ohm speakers and was not ever pushed to its limits.

A visual inspection of the caps inside showed nothing obvious, leaking, bulging, etc. I am not a technician so my quick inspection was not thorough.\


Capacitors that have failed and visibly bulged or are leaking don't take much skill to detect.  Without those kind of fairly obvious symptoms, its hard to detect a failed cap.

Quote
I read somewhere that a caps life in a power amp is 15 years max.


Capacitor lifespan varies with the type of capacitor. Electrolytics tend to have far shorter lives than other kinds, but still can be good for many decades.  Equipment that runs hot - > 110F  may shorten its life.

The best answer IMO is bench testing to confirm original specs.

Capacitors Lifespan

Reply #6 –
Since I'm not a technician or an electrical engineer, I'm not exactly sure what type of capacitors they used. It is an "audiophile" amp and I fully realize there is no such thing as an "audiophile" capacitor, but I would think that they would have used a reasonable quality level that would hold up to heat and time. It came with a 'lifetime' warranty, but of course doesn't mean that parts last forever.
Ad hominem attacks are not Science.

Capacitors Lifespan

Reply #7 –
Electronics tend to rely on strict tolerances, sometimes to the molecular and even atomic level, to function properly. Manufacturing discrete components isn't something that lends well to hobby or small shop manufacture. The best results are obtained by large output manufacturing where there is specialized equipment (sometimes in the billion $ range) designed to meet the strict tolerances needed.

"Audiophile" gear isn't made from pixie dust and you can be pretty darned sure that the discrete electronic parts are sourced from the same mass production lines that supplied the parts in the $300 AVR at Best Buy. If the parts in an amp actually are "custom" or "hand-made" then they probably perform worse than those produced by the larger manufacturing lines.

Certain value inductors are one area where I can see a hand-made variety being of reasonable quality, but even there they won't outperform a similarly speced mass produced device. They certainly won't impart an audible improvement in quality.

Capacitors Lifespan

Reply #8 –
Thanks yourlord, yes, your analysis was fully realized back in the 90's right after I purchased the amp. I knew I could have done just as well buying an amp for far less money. My audiophile delusion was starting to fade rather quickly. The generous warranty they offered was 'paid for' in the purchase price.
Ad hominem attacks are not Science.

Capacitors Lifespan

Reply #9 –
Many years ago, the rule of thumb for old unused electrolytics  was to use a variable AC transformer to slowly increase the voltage to the entire unit to "refresh" them. I have done it in the past and had no problems. I don't know if it is a recommended procedure anymore.
Glass half full!

Capacitors Lifespan

Reply #10 –
Quote
Electronics tend to rely on strict tolerances, sometimes to the molecular and even atomic level, to function properly.
As a generalization, capacitor tolerances in audio circuits are NOT critical.  Usually, there is a minimum capacitance and in most cases you could replace a 10uF cap with a 5uF or 20uF cap and there would be zero effect on the sound.  In almost every case, a higher value capacitor (within reason) won't hurt anything.

Capacitor values are critical in filtering applications, such as EQ/tone controls or speaker crossovers.

BTW - I've got an amp from the 1970s that's still working fine.    ...And, I had another amp that I built, and after sitting for a few years some small electrolytic capacitors literally exploded releasing very toxic-smelling fumes.  I may have not allowed enough voltage tolerance (maybe they were 16V caps running at exactly 16 V or something like that).  After getting out of the room and allowing the smoke to clear, I replaced the caps and it worked fine again.

Capacitors Lifespan

Reply #11 –
Yes, bilbo, the service manual I have states that when starting up the amp after a malfunction or after a long inactive period, a variable transformer is to be connected and set to 0Vac. It then states the voltage should be raised slowly to 10Vac then check the positive and negative rails then check all fuses. There are several more checks performed while continuing to raise the voltage in small increments until 120Vac is obtained.
Ad hominem attacks are not Science.

Capacitors Lifespan

Reply #12 –
Quote from: bilbo on
Many years ago, the rule of thumb for old unused electrolytics  was to use a variable AC transformer to slowly increase the voltage to the entire unit to "refresh" them. I have done it in the past and had no problems. I don't know if it is a recommended procedure anymore.


IME, still a good idea.

Capacitors Lifespan

Reply #13 –
Quote from: DVDdoug on
Quote
Electronics tend to rely on strict tolerances, sometimes to the molecular and even atomic level, to function properly.
As a generalization, capacitor tolerances in audio circuits are NOT critical.  Usually, there is a minimum capacitance and in most cases you could replace a 10uF cap with a 5uF or 20uF cap and there would be zero effect on the sound.  In almost every case, a higher value capacitor (within reason) won't hurt anything.

Capacitor values are critical in filtering applications, such as EQ/tone controls or speaker crossovers.


For about the last decade an increasing proportion of tone controls, crossovers and other frequency-sensitive networks have been implemented in the digital domain, typically using DSPs. They don't depend on precision capacitors or resistors any more.

Capacitors Lifespan

Reply #14 –
Quote
For about the last decade an increasing proportion of tone controls, crossovers and other frequency-sensitive networks have been implemented in the digital domain, typically using DSPs. They don't depend on precision capacitors or resistors any more.

Wow, I guess it is obsolete, time to sell my amp.
Ad hominem attacks are not Science.

Capacitors Lifespan

Reply #15 –
Quote
"The amplifier does not require any maintenance. While the design is conservative, this is a hard running amplifier, as single ended Class A operation is the least efficient operating mode. In fifteen years the electrolytic power supply capacitors will get old. Depending on usage, you will begin to have semiconductor and other failures between 10 and 50 years after date of manufacture. Later, the sun will cool to a white dwarf, and after that the universe will experience heat death."

I found this quote from Nelson Pass in one of his user manuals for one of his amps. Good advice, but a strange sense of humor.
Ad hominem attacks are not Science.

Capacitors Lifespan

Reply #16 –
Quote from: DVDdoug on
Quote
Electronics tend to rely on strict tolerances, sometimes to the molecular and even atomic level, to function properly.
As a generalization, capacitor tolerances in audio circuits are NOT critical.  Usually, there is a minimum capacitance and in most cases you could replace a 10uF cap with a 5uF or 20uF cap and there would be zero effect on the sound.  In almost every case, a higher value capacitor (within reason) won't hurt anything.


I wasn't really talking about electrical specs. I was talking more about the actual physical construction. I can build a cap to meet the electrical requirements out of tin foil and air. It won't be very pretty, or small, and will be prone to "very bad things" happening when physically disturbed during operation. While the paper specs would look fine and I could site the fact that my amp has "hand-made" capacitors, that shouldn't be considered a good thing 

Capacitors Lifespan

Reply #17 –
Quote from: NaturalTimbre on
Hello,

Does anyone know the general lifespan of electrolytic capacitors in a power amp?

I have a (rated 200W per channel 8 ohm load) power amp that is 19 years old. Some of those 19 years have been spent sitting in storage boxed up, the rest of the time it was in regular use.

I purchased the amp new and the amp has been 'babied' all of its life by driving efficient 8-ohm speakers and was not ever pushed to its limits.

A visual inspection of the caps inside showed nothing obvious, leaking, bulging, etc. I am not a technician so my quick inspection was not thorough.

I read somewhere that a caps life in a power amp is 15 years max.


I replace thousands of electrolytic caps in 'vintage' broadcast gear and can tell you with absolute certainty that the units
that run hot will fail fairly quickly. Surface mount caps are by far the worst for failure. Surface mount in a hot unit fail to
total non function is less than 6 years. Most of the time I find surface mount easier to replace as they just 'sit' on top of
the board and are pretty easy to remove with no board damage. Again, the heat that ages the caps also makes the board
more fragile to remove the caps.

Worse are the caps that leak acid which may re-etch the board and remove more copper. Repairing 7 mil traces can get
very tedious as you inevitably miss some damage initially that needs to be to be discovered by troubleshooting with
meters, scopes and test generators.

The same things happen on computer motherboards but they tend to be even more demanding as there may not be thermal
reliefs in the power and ground planes. For those the Metcal iron needs an 'assist' with a hot air gun to get it hot enough as
those planes act as heat sinks inside the board. If you pull on the leads you can damage a plated through hole and ruin the
board. Yes there are times the old computer is really needed and a new one won't do.

I all cases bulging caps are bad but non-bulging are not necessarily good. Also an ESR meter that reads bad IS bad but
reading OK may still be bad. Switching power supplies have the most stringent requirements and need the best parts you can
get. 'Best' is largest ripple current followed by highest temp and longest hours. I've been asked if I worry about 'price' of
the caps. On a busy day I might use $25 in caps which is a pittance compared to the labor.

Rule of thumb. If you find a bad cap of a certain value or manufacturer, replace ALL of the same value. Some of the units I
work on are such a PITA to get open I simply replace ALL the caps with no regard as to what might be OK. It also helps that
I get to buy parts in 1000 lots which brings the price down a lot.

BTW my 25 year old Adcom amp has all its original caps though the main filters are showing signs on the scope of End Of Life.

G²