>Richard 2@mail.vcnet.com
>Fri, 26 Apr 2002 13:12:30 -0700
> . . . Digi-Key sells 500v-rated
>100k-ohm, 3w resistors, also mfg by Panasonic, which make suitable V
>equalizers.
A Mallory engineer back in the 1960's put a non-equalized electrolytic
string in a published project with the admonition that such R/eq were
folly since during failure-mode they actually worked against the best
interests of the individual failing electrolytic cap. And even hastened
the avalanching of the entire series (but don't hold me to this part of
it). I just remember this as sage advice from someone who should really
know.
He described failure-mode of, say, one of the electrolytics as offering
'zero ohms resistance' at turn-on and continuing as such over the ensuing
seconds when normally it would begin developing a Vb, ie, 'taking a
charge'. As it persists in this obstinant state it presents a 'short' to
the string, thus a resistor across it will be of no significance
whatsoever. And the presence of resistors across the others likewise is of
no value to them either, good cap or bad.
If our obstinant cap suddenly pops 'good' it does so on its own. The
presence of that resistor does not assist. If it remains 'bad' the rest of
the string simply remains under the new parameters giving the good caps a
bit more voltage each. Note, I'm not saying a failed cap will ever 'pop
good' again- just trying to cover all possibilities.
I noticed in the Gi7b transmitters that the 6m rig HAD R/eq in the ps, but
that the hf rig did NOT. Odd. Then a bit later I noticed Richard's comment
above.
Kilo-pardons to all on List if this topic has been hashed out before- a
global search did not seem possible.
Bill K2AME
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