[AMPS] Gassy Tubes and Gas Arcs

[Rich Measures]

>>>So then if all of the tube isn't evacuated, none of it is evacuated. 
>>>
>>The evacuated space acts as one entity.  The space is pretty well 
>>evacuated and sealed at manufacture.  If a glass to metal seal has a 
>>microscopic imperfection, the vacuum fades as air invades.  
>>
>Right.  In other words, the entire tube inside the glass is "evacuated" 
>space.  So the glow from the beams striking the glass envelope is in the 
>evacuated space.  

no.  The glow is from within the glass.  

>Other people have pointed out that if the tube is gassy 
>I would see the blue glow *inside* the anode assembly.  

Seeing inside the anode is difficult.  The glow I see is typically in the 
space between the lower outside of the anode and the grid or screen 
collet.  

> In other words 
>look in between the holes in the plates and see if the blue glow is in 
>there.  This explanation made the most sense to me.
>
>So there is no difference between one area inside the tube and another in 
>terms of the vacuum.  Either it's all gassy or it's got a good vacuum.  
>
semi-yes.  Less than 10 or so uA  @ 8kV of cold leakage in 3-500Z means 
the vacuum is good enough.  However, new ones often measure less than 1uA 
@ 8kV.  
 
>Perhaps we are saying the same thing and I am misunderstanding what you 
>were saying...
> 
>>>But you said that one blue glow is from electron beams striking the 
>>>envelope.  The other is in the "evacuated space."  How do I know which 
>>>from which?
>>>
>>By observation.
>
>Well, since the glow from electrons hitting the envelope does occur 
>inside the evacuated space, it's kind of confusing by your definition.  I 
>think what you are trying to say is that if the blue glow happens at the 
>surface of the glass envelope, then it's not a problem.  If the blue glow 
>happens in the middle of the free space inside the tube, then it's gas.
>
yes



Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


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