Commander Kinsey wrote:
What's wrong with crossposting? There are 4 groups where people might
know the answer. Yes, I could post 4 times seperately, but then people
wouldn't see each other's replies.

I've checked both Ebay and Alibaba (where you can buy huge bulk
quantities), and the prices are no different.

I've never seen the tantalum ones break.


On Sun, 09 Feb 2020 16:06:41 -0000, Brian Gaff (Sofa 2)
wrote:


Stop excessive crosposting...

I suppose cos they can get them el chepo. I also have found toward
the end
of the 90s, those little tantalum caps that look like blobs of resin
coloured blue tend to go leaky and damage the rest of the circuit.
Nothing is supposed to last any more.
Brian

This is copied from the web page of a capacitor company.

Pros of aluminum electrolytic capacitors:

Higher voltage ratings available (up to 600V)
Way cheaper pricing (for the same capacitance and voltage)
Better leakage current behavior than polymer

Pros of polymer electrolytic capacitors:

Lower ESR/higher allowable ripple current
No dry-out behavior (unlike aluminum capacitors)
Higher expected lifetime/load life

And while one biased company claims electrolytics
dry out after 3 years (a made up number), another
company (likely using field statistics for their
own capacitors) finds the time constant is 17 years.
And I would have to conclude that the 17 year number
is likely to be closer to the truth (based on old computers
still in a running state, like my first computer from
1998-1999 or so which still operates just fine).

The Arrhenius effect is for real, and operating even
the best electrolytics at high temperature, doesn't
end well. At the highest allowed temperatures, some
of these electrolytics (by calculation) should only
last for 2000 hours. That's what the curve fit data
for accelerated life testing shows. When I say a
number like 17 years, it would be in an item with
proper and copious cooling. Note that electrolytics
themselves get warm in service, depending on the
ripple current being forced through them. The plastic
sleeve on the outside, does not enhance cooling for
those situations. The capacitors in VCore (on the primary
or secondary side) could be experiencing high ripple currents.
And if any are to fail, those should go first. The
"bulk" decouplers placed near a PCI or PCIe slot,
those aren't under nearly the same stress level.

HTH,
Paul