Better yet replace them with higher voltage rated ones if they are available. 20V tantalum lasts
forever
on 5V rail as well as 35V one on 15V.
Well, yes. All I'm saying is that I have identical plugins (such as 7A26) in which at some point Tek
went from tant bead to aluminium electrolytic. So substitution is tried and tested.
And low ESR is not as good for tantalum beads as compared with modern low ESR aluminium
electrolytics designed for switched mode supplies. As an example an AVX 47uF 35V tantalum bead has
an ESR at 100kHz of 0.8 ohms. A Panasonic FR of the same capacitance, but 25V rated has an ESR of
0.3 ohms at 100kHz.
I can send you a handful :) They _ALWAYS_ leak sooner or later because of their very chemistry.
They
are filled with sulfuric acid and although silver sulfate has very low solubility it is still not
zero so sooner
or later that nice silver can turns to sieve. And the fact they are almost always used at their
rated
voltage or even above also doesn't make them last longer...
Operating any capacitor at or above its rated voltage is a short term recipe for capacitor death
regardless of chemistry. Even with wet tant, the current recommendation is that for long life the
rated voltage should be at least 1.6 times the operating voltage.
I have dozens of those leaked in 492BP/494AP SAs that I refurbish on a regular basis. The same is
true
for those HP 835xx microwave plugins that I revived quite a few -- I have never seen a single such
plugin that didn't have at least one leaked wet tantalum. The most spectacular was one 83572A
plugin
where sulfuric acid from one big wet tantalum ate off it leads completely, spilled on the
motherboard
and ate a hole through the entire motherboard PCB, through all of its copper and fiberglass
layers.
That is impressive! Were these rubber sealed versions?
Craig
