[R-390] Gettering old tubes
2002tii
bmw2002tii at nerdshack.com
Wed Mar 2 15:01:47 EST 2011
Ben wrote:
>maybe put together a chassis with multiple sockets and a filament
>supply to keep your tubes warm
Filaments alone won't even get the envelope to full operating
temperature, so this would only be better than storing them at room
temperature if you did it constantly for all of your spare
tubes. And then, you'd have to worry about (i) the decreased
in-service heater life due to the "storage" operation of the heaters,
(ii) "cathode interface," and (iii) the deposits of cathode oxides
boiled off and deposited on the grid. When the tube is operating
(drawing plate current), most of these boiled-off cathode oxide
molecules are moving too fast to deposit on the grid. When the tube
is cut off, they are drifting slowly and tend to deposit on the
grid. Cathode oxides on the grid lead to grid emission and thermal
runaway when the tube is operated.
Best regards,
Don
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