Roger Weichert wrote:
> I've been going to ask for a while about possible causes for the
> failure of some 10,000uF 35v electros that are used in a basic power
> supply for a pulsation controller.

The basic causes for electrolytic cap failures are:

1 - Poor manufactured quality.  This is one of those things where
    brand does matter.

2 - Voltage stress.  There isn't a hard limit at the voltage rating,
    so creative specsmanship can be a factor (see #1).  For long
    life it's a good idea to derate the max voltage by a comfortable
    margin.

3 - Temperature.  Again, no hard limit, reputable suppliers may
    leave more margin in their specs.  Derate for long life.  Note
    that high ripple current causes dissipation, which increases
    temperature, which decreases life.  Caps meant for this kind of
    application have a ripple current spec, like Panasonic FK
    series.

> I've uploaded an image at http://imagebin.ca/view/HX_1Ati.html

It's a little hard to tell how tall these caps are, but they look
surprisingly small for 10mF and 35V.  Does it look like 6 Joules can fit in
there to you?  Look up the size of caps of the same rating from reputable
vendors.  If those turn out to be bigger, then it's pretty clear what
happened.


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