Re: What replacement for 22uF tantalum beads?


 

On 18 Mar 2016 09:18:12 -0700, you wrote:

My 485 is, of course, full of 22uF tantalum PTH beads used for
bog-standard decoupling; the first has just shorted out.

Looking for direct replacements shows that low voltages
are readily available at sensible prices, but that the price
of anything above 16V is relatively silly. Being somewhat
stingy, I'd like to use a more modern technology at a
reasonable price.
You might consider only replacing the solid tantalums which have the
same voltage rating and voltage derating. The others are less likely
to have a problem unless they were not voltage derated.

So, what do people replace them with?

1) Nishicon aluminium electrolytics - if so, which
/range/ is preferred (I suspect this will be my preferred
option, provided performance is satisfactory
I like the Nichicon PW series but any low impedance and high frequency
aluminum electrolytic capacitor intended for switching power
applications will work. The capacitance of the aluminum electrolytic
capacitor should be about 3 to 4 times the capacitance of the solid
tantalum capacitor to get an equivalent ESR and D.

2) SMD tants directly soldered onto the board (SMD is
/much/ cheaper than PTH)
This is a great idea assuming the parts will fit between the existing
plated through holes. I am surprised they are that much less
expensive.

3) SMD tants soldered onto a tiny carrier board with
"legs" on the other side. Fiddly but practical.

4) the exorbitantly expensive direct replacement
tant PTH beads
I am surprised they are that expensive. If you live in a major
metropolitan area, you might check out local electronics surplus
places for inexpensive NOS (new old stock) solid tantalum capacitors.

(Some tant beads appear across potentiometers.
I wouldn't replace those with aluminium electrolytics
since they have a significantly higher leakage current
which might affect the pot's setting.)
The leakage is not *that* great and they do make low leakage aluminum
electrolytic capacitors.

I care about performance, not about the "authentic
purity" of any reworking.

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