Life of Electrolytics

[Khas Evets]

I have some vintage pedals in the 20+ year old range. I've read that electrolytic caps have a useful life of 5-10 years. The pedals sound fine and I'd like to avoid cutting up a vintage pedal, but if the caps are due for an upgrade I'll do it.

What are the signs that a cap is failing (leaking DC, increased tolerance, added noise)?

[Peter Snowberg]

Electrolytic life is a funny thing. They really don't like to sit there unused. If the cap is in use, it will 'heal' itself to a good degree.

The time you often see associated with electrolytics is the shelf life and it's HIGHLY relative to how that cap is in service. In tube amps the caps really have to work hard and they do it in hot environments.

The electrolyte used will also determine how long the thing lasts. There are at least four electrolyte systems for aluminum electrolytics that I know of. I'm sure there are plenty more.

Big, high voltage caps are the ones to worry about. I have tons of other equipment with 30 year old electrolytics that are doing just fine.

[Paul Perry (Frostwave)]

I never change anything in gear (old or new) unless there is DEFINITELY a problem (by problem I mean , it doesn't work at all, or there is smoke or hum).
Fortunately, failure mode in caps in low voltage gear (stompboxes) left on a shelf for 30 years is almost always just low or no capacitance due to drying out, & you can check this by simply putting a good cap in parallel with it. If it improves, then you have likely found a dried cap.

[makkimo]

oh my god!!!
that meens all my works using 100v electros are destined to die soon.......?
:shock:  :shock:  :shock:  :shock:  :shock:  :shock:  :shock:

[petemoore]

  We're talking days or months, not years.  :twisted:
 Just Razzing...[IIUC]
 I don't know what the ratio is on these caps as far as what makes 'em die...
 Shelf life seems to be top cap killer
 Temperature/humidty/environments seems to play a role
 I haven't read reports of evidence that using larger voltage rating than needed caps actually shortens it's expectancy...seems feasible, I suspect to a small degree though.
 What I read most is never use a smaller rating than the voltage it'll see.
 There are no tonal differences between a 16V 1uf cap and a 1600V 1uf cap [?]...they lOOk so different...

[Brett Clark]

I know that it's just anecdotal evidence, but there were some Fender amps that used high voltage (350 to 500V) caps in the (about 50V) bias circuit. I suppose just because they had them around (for the HV supplies) when they ran out of the low-voltage ones. These are ALWAYS bad (off value or open), in every single example that I have seen in over 20 years of fixing amps, even when the identical parts in the High-Voltage supply were holding up OK.

[R.G.]

Electrolytics more than any other electronic component except the batteries they resemble will die. Of this we can be sure.

The only question is when.

Electrolytic life is compromised by
(a) shelf life with no bias on them
(b) bias voltages much lower than the rated one
(c) HEAT - if you wanna kill them, roast them.
(d) even short reversals of polarity if current is not strictly limited

If you want your electros to last a long time, use them at about 75% to 90% of rated voltage, and keep them under about 50C. Life is cut by half for ever 10C rise in temperature, whether the temperature is generated inside the cap by high pulse currents or from outside cooking.

I personally do not believe that there is any such thing as a "vintage electrolytic cap" sound. So I replace electros that are over 20 years old as a matter of course. I was taught this by working on solid state Vox amps. These have a bazillion electros in them, and if you get one that's not working, odds are quite good that replacing the correct electro will fix it.

I have done this on a couple of my amps now. If you fix it piecemeal, you will be debugging to find and replacing a cap or two every few months for years. When I get one of these amps now, I arbitrarily replace ever single electro in them.

Same for effects. I recommend this in my "Guitar Effects Debugging Page". In this respect, Paul, we disagree. I **hate** re-fixing something I had to work on once. And I find that chain failures are common on really old gear, especially cheaply made (can you say EH? I thought you could) stuff.

Lastly, if you want to hear what it sounded like when it was new, put in new electros.

If you simply must do it one at a time, get yourself an ESR meter. This magic meter will not tell you the capacitor's value, it will tell you how much parasitic resistance has built up, hence how dried out the cap it. You can literally probe through a chassis and replace the bad ones out of hand. About $100.

[rubberlips]

Is it only the electro's that dry out? Or do poly's and ceramics do the same thing??

Pete

[Paul Perry (Frostwave)]

I don't actually disagree with RG on cap replacement. If I was a genuine EE & I could quicky and easily fix anything I broke accidentally while desoldering old electros, then sure I would recap stuff at the first sign of trouble!
But I'm me (for better or worse!) and that means, if I open somethign up to work on it I'll probably loose the screws, or clumisly short the power rail to a SSM chip, or get distracted & put the unfinished project somewher the cat can get at it..
The bottom line is, dependign on the gear & the guy, sometimes it makes sense to recap!! but not just for the hell of it.
By analogy, I havn't been to a doctor for over a decade. I've been ill a couple of times, but.. unless something is life-threatening, there is usually nothing a doctor can do that is useful. I *DO* eat and live right, the same way I treat my gear!!
Of course, some people ENJOY having a doctor perform a complete walletectomy :lol:

[rubberlips]

I agree with you there Paul. Since I moved to the country, I haven't had to see a doctor for 3 years, except for the work related back problem - I was seeing a chiro who recommended seeing a doctor to get some pain killers while the back was rcovering. Generally rest and recovery time is needed - unless you get cancer  

Pete

[R.G.]

Only electrolytics have this problem. Other caps have no inherent wearout mechanism like electros.

[Toney]

Well I've done my old Amps and was just getting all satisfied with the elctro aging issue......hadn't really thought about my older pedals.

But.... seeing as the pedals I do have and love are mostly from the early  
eighties , I guess they re "due" for electro replacements

God , something else to bother myself with.....