[Amps] Arc distance and plasma

[Will Matney]

Bill,

I'd say that was gassy, hi hi! I'll bet it would have lit up if plate voltage had been on it. On receiving tubes, and sweep tubes, when they've lost their evacuation generally from a crack in the glass at a pin, they will actually light up all over the place. You can quickly tell one of these as the getter flash on the glass has turned white. The color of the light is violet to white. I guess what I've seen would have been gas pockets or something as these ionizations of gas happened in different places all inside the envelope. I actually let one of these run one time for a while just to watch it. Luckily, it didn't ruin the B+ supply. Less gassy tubes of course have a violet colored glow inside the anode. This is visable through holes in the anode where you can see inside. The smaller receiving tubes will have a glow also, but may be a little harder to see due to their size.

Best,

Will

*********** REPLY SEPARATOR  ***********

On 7/28/06 at 11:00 AM Bill Fuqua wrote:

>I had just gotten some odd tubes on ebay (4x-500)  which were basically 
>4x500 tubes with a 4-400 base. I figured that they were bad but thought
>I'd 
>just try them on my tube tester anyway. I lit up the filament on one and 
>could see smoke curling up in the inside. That is just not right! They
>were 
>obviously at atmospheric pressure inside. Those were really gassy tubes.
>
>73
>Bill wa4lav
>
>
>At 10:51 AM 7/28/2006 -0400, Tom W8JI wrote:
>>Rather than claim I can look at a tube and magically tell
>>what happened years ago with my magnifying glass,  I thought
>>I would add a picture of a 3-500Z under RF plasma
>>conditions.
>>
>>The photos clearly show then concentration of plasma during
>>a hard fault.
>>
>>http://www.w8ji.com/fault_protection.htm
>>
>>Enjoy.
>>
>>73 Tom
>>
>>
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