Capacitor Life Expectancy

[claytushaywood]

I commonly see posts about electrolytic or tantalum capacitor's having 'short' life expectancy.  Is this really something to worry about?  I've seen plenty of pedals built in the 60's and 70's with perfectly functioning caps... i'm sure if they're used a lot the capacitance could have changed.  Also it seems that amps with failed power caps tend to be ones that were out of use for long periods of time. 

I found this calculator on the illnois website.  I'm not sure of the "load life expectancy" but I plugged in some common values and it looks like these nichicon caps I have could outlive me plugged in 3 hours a day.

[dont-tase-me-bro]

I think that is life at max temperature.  I don't know if that means ambient temp, or if they heat up internally during use

[pickdropper]

There are a whole bunch of factors: temperature and ripple current are probably the most common.  For guitar pedals, temperature is usually not much of an issue.

If the cap uses a liquid dielectric, that will eventually dry out over time, causing the cap to fail and require replacement.  It's usually over many years (decades) but lower quality caps can exhibit this problem sooner than that (look up the capacitor plague).

There is a bunch of info here that is fairly interesting:

http://www.nichicon.co.jp/english/products/pdf/aluminum.pdf

But, in the end, it's expensive to get the capacitances you are going to want for power filtering.  If you stick with high quality electros from name brands (I'd personally skip the Tayda variety) then you are probably going to be fine for a long time to come.

[lars]

Best bet, get an ESR meter. Sometimes caps can last a long, long, long long time.