I've seen quite a few computer motherboards with bulging or leaking electrolytics, but I'd agree they were likely lower quality.
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Capacitor lifespan
- Thread starter agedhorse
- Start date
The capacitors might have failed prematurely, but it’s equally likely that your friends tried to run the pedals at a higher voltage, or accidentally plugged a power supply into the pedal that supplied AC instead of DC.
Me too! I'm also always told that when I speak I remove all doubt.
I worked for years at a company that built graphic digitizers. At one point the owner, in his frugal zeal, second-sourced a small ceramic disk cap, something akin to the caps we use in passive bass tone circuits. Turns out they were completely out of spec and every control board built with them would not work. Drove the bench techs nuts until they zeroed in on the problem. Luckily the boards were only rendered inoperable, not ruined. New cap, all good.
The Bar Band Bassman
The Bar Band Bassman
Interesting info here, are there components that commonly fail while simply sitting in storage unplugged? I put a class d head away in a closet in my house that was functioning, then maybe 6-7 years later I pulled it out and it's just putting out a sort of electrical pulsing noise and I was afraid it was going to blow my cab so I shut it off right away. Even the power light was pulsing. I imagine that's not much to go on but any ideas?
- Feb 12, 2006
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- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
I abide. 25 years of building / modding tube amps, never a problem with a cap. Even on 40 years old Marshall amps. The only one I ever had in my house was the 250V cap in some of the blinds command module (and we have 230V here). I opened the modules replaced the caps with er... Orange Drop 400V. No probs ever since.
And yet on many things i have to repair (not only audio) there is caps loosing their values or leaking.
For example, I repaired a Koch amp which had a bad set of caps resulting in wind noise in the speaker.
Or my actual Daikin AC/heater is failing when it's too cold outside because of bad MKP caps degrading the comm between out unit and in unit.
Life span? 4 years.
I'm not saying it's always the capacitors but i always check them quickly.
My check routine is in this order:
Isolation/ground
Connectors / cables
relays
capacitors
... and the rest.
I agree with agedhorse - I think it's sacrilege not to 
that not all electrolytic capacitors are destined to fail after 10-30 years, especially in the well designed and high quality circuits he engineers. However, I think it should be made clear that caps can fail well before their time.
Some caps can operate for 50+ years... IF they're properly constructed with high quality components and put in a well designed circuit that's not subject to misuse (someone connecting the wrong power supply, connecting a 2 ohm load while turning all the knobs to 11, etc.) and not exposed to detrimental environmental conditions (heat, freezing cold, humidity, liquids, lightning, vibration, shipped via UPS / FedEx without padding, etc.)
Many years ago I was a victim of "the capacitor plague". A cap in my video card exploded. Easy fix, but the video card was only a couple years old.
A quick search at Invalid Link Removed shows there are some aluminum electrolytic caps only rated at 500 hours of lifetime. Yes, that's the bottom end of the scale, but obviously not all caps are intended to run 50 years.
Bottom line, some caps can run 50+ years, some can't.
that not all electrolytic capacitors are destined to fail after 10-30 years, especially in the well designed and high quality circuits he engineers. However, I think it should be made clear that caps can fail well before their time.Some caps can operate for 50+ years... IF they're properly constructed with high quality components and put in a well designed circuit that's not subject to misuse (someone connecting the wrong power supply, connecting a 2 ohm load while turning all the knobs to 11, etc.) and not exposed to detrimental environmental conditions (heat, freezing cold, humidity, liquids, lightning, vibration, shipped via UPS / FedEx without padding, etc.)
Many years ago I was a victim of "the capacitor plague". A cap in my video card exploded. Easy fix, but the video card was only a couple years old.
A quick search at Invalid Link Removed shows there are some aluminum electrolytic caps only rated at 500 hours of lifetime. Yes, that's the bottom end of the scale, but obviously not all caps are intended to run 50 years.
Bottom line, some caps can run 50+ years, some can't.
Like anything, a cap can go bad in a day or 50 years. But changing them as a matter of routine is silly. Apparently you didn’t, so not pointing fingers at you. But for those who do change them after a certain amount of time whether they’ve gone bad or not, hey, spend your money foolishly if you want.
Basically my routine too.
1) Look for burnt components.
2) Loose connections.
3) Relays, switches (burned / oxidized contacts).
4) Caps.
5) Actual troubleshooting.
This question kinda reminds me of the discussion about necks not being under tension (Warmoth necks are made and shipped with no tension on them, and it doesn't seem to hurt them). Is there any functional difference between a new capacitor that has been sitting on a shelf for years before being installed on anything, and that same capacitor being in a piece of gear that hasn't been powered up for years?
What really "stresses" caps (note the quotation marks) is power cycling. Not saying this to discount whatever you said, hey?
That said, it does make *some* sense to check caps in older equipment. Not all audio equipment was built to a standard (never mind a mil standard). If you are scouring through yard sales and picking up older budget gear, for instance, it is sensible to do so. But yeah, it shouldn't be a blind replacement.
These are crucial. I have seen electrolytic capacitors tested according to manufacturers specs and not all did what they promised. Also, life time is heavily depending on the temperature they build up, and more heat means lesser live span, and that decreases fast when temperature rises.
I had a learning experience a few years ago fixing an old late 60s British 100 watt 4x EL34 Carlsbro that came to me passing signal but with a loud hum. I went for the classic blind replacement of filter caps, but it turned out that only the smaller electrolytic in the bias supply had actually failed, and the amp would have run quietly if I'd diagnosed first and replaced just that. I don't know if the half wave rectifier in many bias supplies is harder on them, perhaps.
I've replaced literally a couple of caps on automotive PCM's over the course of a 30 year career. Only one was a leakage failure, but still functioned. The others were specifically water damaged to the legs from a flood situation, having nothing to do with normal service lifespan. Of note, I worked on modern and vintage autos, seeing to vehicles that pre-date capacitors in regular service applications.
"I drink a cup of coffee, then the sun comes up everyday, therefore..."
Confusing correlation with cause is a real bugaboo when you're troubleshooting equipment problems. Decades in a totally different industry than @agedhorse, but it was still a real challenge. Get called in (why it is always 2 am on Sunday?) and I hear "We think this is the problem". Well, thanks for trying and not just walking away from it, now tell me what's going on.
Confusing correlation with cause is a real bugaboo when you're troubleshooting equipment problems. Decades in a totally different industry than @agedhorse, but it was still a real challenge. Get called in (why it is always 2 am on Sunday?) and I hear "We think this is the problem". Well, thanks for trying and not just walking away from it, now tell me what's going on.
Electrolytics like (OK, need) to be biased - they're (kinda) batteries, and if they get too much voltage applied, they don't last very long. If they get reversed biased, the don't last too long. Pedal designers will often put electrolytics in places in the circuit where they might be biased forward, they might not be biased at all, or they might be a bit reverse biased. There are a lot of pedal designers (boutique folks and the like) that aren't really educated on how you should bias an electrolytic, and as a result, yes, there are places where 'lytics don' t last long. The reason this happens is because...you can get away with it for a while (electrolytics are somewhat forgiving), but if your products are out in the field for a decent amount of time, you will eventually run into the problem. If you design your circuits right (it takes an extra part or two at times), then your lytics can last a long time.
There are places in certain circuits where you have to work at it to protect your lytics. A lot of gear has balanced outputs, and runs on internal positive voltage supplies. So, you're AC coupling the output of the device to protect the next piece of gear. So, you put an electrolytic on the output, with the positive end pointed "in" - the circuit is, voltage wise, above ground, and ground potential is what you will get (most of the time) on the other side of that electrolytic. So, that capacitor is biased forward, and you're good. But..wait, the output might be hooked up to phantom power. If it's a line output, it shouldn't be, but in a mess of xlr cables, hooked up to a mixer, that could easily happen. So, if you like your customers, you need to protect against that. Phantom power is 48 volts, so...a 50 volt electrolytic, with the plus end pointed out will do the trick. Oh, but Phantom can be 52 volts (it's 48 plus or minus 4), so we now need a 63 volt electrolytic (the next step up voltage rating wise), and.. if phantom isn't there (which it isn't most of the time), that capacitor is unbiased, which is a bad thins. So, you put a small amount of negative voltage on the "inside lead" of the thing to make sure it always is, and you have resistors between and after the 'lytics to deal with any leakage current. This all adds up to a lot of parts, and space taken up, so a lot of times it isn't done. You can use a transformer, which side steps some of this, but not all of it, but that also takes up real estate, and is a bit pricey. It's a tradoff that you have to understand well to make the right decisions.
The point is, electrolytic capacitors are very useful devices, but if you want them to last a long time, there is some work that needs to be done right in the design to ensure that. In old tube amps, that stuff was well understood, and the voltages are all big positive numbers - they all ended up biased forward, and if you put one in backwards, you found out as soon as you plugged it in (electrolytics fail in sometimes spectacular ways - they can spew their guts out). With solid state devices, there are more places where you can put an electrolytic where it'll last for a while, but not many decades.
I worked for a company where we did pro audio circuitry, among other things. We made sure we schooled new Engineers in this kind of stuff - it isn't really covered in most EE programs in school - the field is too wide nowadays to cover analog circuitry stuff like this in depth.
I’ve seen leakage failures and I've seen electrolytics explode from over voltage leaving nothing but shredded paper all over the circuit board.
I’ve never replaced caps after buying used amps. I’ve got one that is still going strong after 60 years.
I’ve never replaced caps after buying used amps. I’ve got one that is still going strong after 60 years.
The only times I ever saw a popped electrolytic cap was during the 90s on some computer motherboards. It was an industry issue for a while. It was caused by the poorly spec’ed and cheap capacitors some manufacturers tried using.
The only other one I saw was in an antique (~1930) piece of radio gear someone found in their attic and gave to my father in the late 60s. He was a radio guy in the navy during the war and able to repair it. And I do remember him saying it wasn’t the capacitor itself that failed. He said the classic mistake people make when troubleshooting electronics is to mistake a symptom (i.e. failed component) for the cause of the problem. In this instance it was a faulty resistor elsewhere in the circuit that caused the cap to become damaged. It also barfed up a tube if I recall correctly.
The only other one I saw was in an antique (~1930) piece of radio gear someone found in their attic and gave to my father in the late 60s. He was a radio guy in the navy during the war and able to repair it. And I do remember him saying it wasn’t the capacitor itself that failed. He said the classic mistake people make when troubleshooting electronics is to mistake a symptom (i.e. failed component) for the cause of the problem. In this instance it was a faulty resistor elsewhere in the circuit that caused the cap to become damaged. It also barfed up a tube if I recall correctly.
