[sdiy] Starter Components - Capacitors

[Roy J. Tellason]

On Wednesday 12 January 2005 05:46 pm, Senso wrote:
> > > If you get offered some cheap caps at bigger than the values for there
> > > normal range (10uF polyesters, 2n2F polystyrene etc then snap em up
> > > :-))
> >
> >I know there was someone on eBay selling axial 100n polystyrene's (+-20%
> >tolerance?!) for about a buck a piece not to long ago.
>
> Good deals are always tempting, but what about the production date &
> shelf-life of caps? Especially on eBay or similar places, you'll never know 
> how old they are...

I have *lots* of salvaged caps,  and I think that concern is fairly 
over-rated,  unless you have them in a higher-temperature environment.  I do 
own a B&K cap checker,  and got it because I did have a problem with some,  
but that was *real* old salvage,  out of tube-based gear, and it was 
tube-based gear I was working on at the time -- an Ampeg SVT if memory serves 
me correctly.  :-)   I weeded out most of what was bad back then,  and 
haven't had that much of a problem since.

I guess it also depends on how close you try to go to the specs of the parts.  
Like people who use a 16V electrolytic in a circuit with 12V power -- I'd use 
a 25V part there,  minimum.  Also,  temperature plays a big role in 
shortening those parts' lifespan,  and I've seen manufacturers do some 
*really* dumb things sometimes,  in an effort to minimize costs.  A slightly 
larger board just isn't going to make all that much difference in a one-off 
hobby project.