[Moon-net] Moon-net Digest, Vol 134, Issue 10

[Rex Greenwell]

Hello Steve -

The gettering agent in the large glass envelope Eimac tubes is coated on the
anode.  The getter activates via the hot anode.  You might have a chance to
degas the tube by operating it at an anode voltage low enough to preclude
arcing, while yet biasing the tube to draw anode current sufficient to
generate plate dissipation approaching the rating of the tube, and holding
it there for some time.  This would create the heat needed to activate the
gettering agent.  For example, if the tube can hold off 2 KV without arcing,
bias the tube to draw 450 ma static current (no RF drive) to generate 900
watts of plate dissipation.  That heat should, given time, and it may take
some time, activate the getter and remove gas from the tube.  While doing
this be sure to keep the amplifier's cooling system in operation. 

73 and GL
Rex K0KP EN36

>My 6M amplifier is currently down, and I am QRT off the moon for the
>moment. 
>The problem appears to be a gassy 3-1000Z, which arcs over  periodically.  
>Can you "cure" a gassy tube?  Thanks in advance for all  your help and
>advice.
>Steve
 
>Steve  Gilbert
>K1SG