[Milsurplus] OK Smart People - Mystery 211s

[Bruce Gentry]

Another method  is to use a neon sign transformer to apply high voltage 
to the tube with no power on the filament. Connect one side of the 
transformer to the filament and grid,  and the other side to the plate. 
A 5000 volt transformer is usually enough, or you can use 1/2 of the 
winding on a standard 15.000 volt because the center tap of the 
secondary is almost always connected to the case. A gassy tube will glow 
nicely, but usually starts to dim and stop glowing as the gas is taken 
up. It may take an hour or more, so don't give up too quickly.  If the 
getters are still silvery, you have a good chance of saving the tube.   
Getters work by both chemically combining with the gas and 
absording/adsorbing it.  The high voltage ionizes and heats the gas, 
causeing the getter to take it up more readily.   Good luck!

      Bruce



David Stinson wrote:
> Just finished testing my stash of 211 transmit tubes 
> by putting them in the BC-375.  
> More than half were bad- mostly gassy.  sniff....
>
> Anyways, here's a mystery:  A few would not 
> draw much current or put out much power in the
> PA stage, but they seem to work just fine
> in the Oscillator stage.  If this was low emission,
> I'd think they'd fail in either stage.  As a result,
> I've got four tubes marked "OSC ONLY."
>
> What's up with this?
>
> 73 Dave AB5S
>
>
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