[Boatanchors] Smart People: Gassy Tubes Reversable?

[Jim Wiley]

There are  two types of "glow" seen in vacuum tubes.

The first is due to internal gas contamination, and appears as a glow 
between elements or in severe cases, throughout the envelope.  If the 
gas contamination is severe, the normally silver appearance of some or 
all of the "getter" on the glass can change to a white color.   Tubes 
that have been severely abused can become gas contaminated by metal 
particles literally blasted from the plate or grids.

The other case, which is a normal effect or operation,  is caused by 
accelerated electrons missing the plate and colliding with the glass 
envelope.  This type of glow appears only on the glass, and usually with 
power tubes, especially beam power types, such as the 6L6 family and 
similar tubes (5881, 6550, etc) (only the glass envelope versions, of 
course).

VR tubes such as the 0A2 and 0D3 (and other like devices) are a 
different case.  They are supposed to glow when operating properly.

- Jim, KL7CC


On 12/3/2013 4:27 AM, Bry Carling wrote:
> Dave
> The purple glow is quite common in some power tubes like 6V6 or 6L6 etc. They often seem to work fine otherwise.
>
> Bry Carling
> http://af4k.com
> Sent with my iPhone 6
>
>
>> On Dec 3, 2013, at 8:18 AM, "David Stinson" <arc5 at ix.netcom.com> wrote:
>>
>>
>> ----- Original Message ----- From: "Jim Wilhite" <w5jo at brightok.net>
>>
>>> What are the symptoms you are seeing in those tubes?
>> Been doing some work with master oscillators.
>> When used in a oscillator stage, gassy tubes "wander around"
>> once they heat-up.  The more gas, the more they wander.
>> I've had several tubes that show no gas response at all
>> on a TV-7 but when installed in-circuit, they "take a walk."
>> I believe it's gas because I have a couple of tubes with visible "blue glow" that show one extreme of the effect
>> and non-gassy tubes that show the other extreme.
>>
>> 73 DE Dave AB5S
>>
>>
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