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RE:- Re: OLD Tubes/Coils (fwd)
---------- Forwarded message ----------
Date: Wed, 26 Feb 1997 20:50:07 GMT
From: Robert Michaels <robert.michaels-at-online.sme-dot-org>
To: mod1-at-pupman-dot-com
Subject: RE:- Re: OLD Tubes/Coils
M>Hello tube coilers,
M> This is something of an epitaph. I was informed
M>by a work colleague today that he chucked out a couple of 833's some
M>time ago after deciding there was no use for them. Then he further
M>rubbed it in by telling me that one was brand new and in a padded
M>carton. Can you believe it???? What has gone wrong with the world?
M>Tearfully,
M>Malcolm
There, there, there...console yourself.
As I pointed out in a recent post (were your eyes too
teary to see?) such tubes are neither scarce or particularly
expensive (yet -- give it another decade).
They are being manufactured every day in Communist China
and Eastern Bloc countries and several firms are importing
them in to this country.
Cost in U.S. $ of an 833-class tube is about $30 each in
single quantities from Communist China and somewhat more
from Eastern Bloc countries.
In Tesla coil service such tubes are apt to be used inter-
mittantly and with low duty cycle. Given a little care they
may well last longer than the person using them.
=Always= apply plate power =gradually= after
the filament (and cathode, if used) has come
fully up to temperature. Apply filament power
gradually also. Under-run the filament somewhat
(say 10%) - the life will be greatly increased
(I believe filament life goes as the inverse of
the =fifth power= of the voltage if I remember
correctly [maybe only the =fourth= -- it's
a big factor] )
Likewise, in Tesla coiling we can be most un-fussy about
particular tube types within a given power range and
construction geometry (triode, pentode, etc.)
Here -- take this -- blow your nose and wipe your eyes
and daddy'll buy you a beer...
Condolences,
Robert Michaels