[sdiy] re: ms20 lfo caps

[harry]

Hmmm....

I, for one... do NOT like to operate electrolytics at or near their rated voltage.
I prefer to derate 50%.  I work with high voltage / high power and often do not
have that luxury. Electrolytics operated near their limits almost always have less
life than those conservatively applied in the circuit.

That said.... The major killer of the electrolytic is HEAT... usually caused by
ripple current. Larger, higher voltage units as a rule have more capacity for ripple
current, and so live longer.

Ripple current is not a hard and fast spec... if you tell a manufacturer what ripple current you need, they tell you what life to expect, and vice-versa.

Now... you friend has a point in using electrolytics in applications that do not have
ANY DC bias... such as coupling caps in audio gear, etc. This could allow the
aluminum oxide layer (dielectric) to decay with time. Some folks like to bias these
stages with some DC by design... to prevent this. I prefer to use non-polar electrolytics... or better still, Film capacitors... in these applications.

My rule of thumb is the highest circuit voltage x 100%   (a 35V cap for a 15V
supply). This is also good in bipolar supplies where some failure might double
the voltage across the cap...

Don't want them to blow up now....

H^) harry (who played "toss the lytics into the trash can from across the room"
with another engineer today... I told him it would be "more fun" if I moved the
trash can a little... These were 3300uF @ 450VDC .... BIG cans. Scary to see
them flying through the air when tossed. even SCARIER to see them fly under
their own power... ;)

Dean Stiglitz wrote:

> hmm, i was taught (by a very good, very experienced repair tech, who really does fix anything) that electrolytics like to be near their rated voltage...that they tend to last longer than if you use higher voltage caps...any thoughts???
>
> deknow
>
>  >>  be sure to get 100u @ 16V or better 25 V...

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