The following procedure came directly from a former Eimac tube designer,
who was with the company when they were still manufacturing glass tubes.
<quote>
*************************
If a tube was last used years ago, or was manufactured years ago, or is
new, it's safest to assume it needs gettering. And the suggested routine
is this:
Cooling is of course required throughout.
a. Bring the filament up to rated voltage slowly. For example, run
the primary of the filament transformer through a light bulb, or
similar to limit the shock of turning it on.
b. Then after some time, bring the voltage to the specified value,
and run it for about 100 hours.
c. Then, apply the anode voltage through some current limiting means
for a while, and, finally,
d. Run the tube at a dissipation level near the specified limit for
a few hours.
The reason for this is that the getter needs to experience a spectrum
of temperatures, mopping up different species at different
temperatures. Furthermore, the lowly 3-500Z for example, has getters
at the base of the grid and the base of the filament as well as
sprayed on the anode.
While this conditioning schedule is seemingly over-complicated and
ultra-conservative, it should result in no surprises when putting the
tube into service.
Terms like "a few hours" are vague because different tubes require
different treatment. If we're "burning in" a monster tube that will
cost us $50,000 to replace, we're going to be more conservative than
with a $50 tube.
***************************
<end quote>
--
73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek
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