Re: What replacement for 22uF tantalum beads?


Tom Gardner
 

On 19/03/16 15:50, David @DWH [TekScopes] wrote:

My hypothesis for the failures of old solid tantalum capacitors is
contamination in the raw materials causing defects in the dielectric
which grow over time. Eventually a large enough defect forms that the
solid tantalum self healing mechanism where heating converts MnO2 to
Mn2O3 fails because of thermal runaway.
I had no warning of failure, the 485 had been on foe an hour
and when I came back half an hour later the +13V line was dead.
Now 13<15, but not by as large a margin as I would have liked.
One tant was a short, one 86R6ohm (!) resistor was toasting itself,
and fortunately the 741 has current-limited outputs :)

Currently I'm using 10uF 15V replacements I had to hand, but
they are relatively easy to replace should I feel the urge.

(My s/n is 702507, but I can't date that)

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