[Milsurplus] OK Smart People - Mystery 211s

[J. Forster]

Gettering works better when the tubes are at or near operating
temperature, and are operated at reduced plate294 voltage, as I
sugge4sted.

YMMV,

-John

============


> 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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