[Amps] "Tubes 201" - How Vacuum Tubes Really Work

[R L Measures]

On Jul 24, 2006, at 9:03 PM, Will Matney wrote:

> Keith,
>
> Excessive grid current did, either from being over driven, or an  
> arc from a gassy tube.

Will M.:  Could an unloaded condition cause excessive grid current?
>
> Best,
>
> Will
>
> *********** REPLY SEPARATOR  ***********
>
> On 7/24/06 at 10:28 PM Keith Dutson wrote:
>
>> I am not talking about AFTER the fuse blows.  What current CAUSED  
>> it to
>> blow?
>>
>> Thanks.
>>
>> Keith
>>
>> -----Original Message-----
>> From: amps-bounces at contesting.com [mailto:amps- 
>> bounces at contesting.com] On
>> Behalf Of Will Matney
>> Sent: Monday, July 24, 2006 9:33 PM
>> To: amps at contesting.com
>> Subject: Re: [Amps] "Tubes 201" - How Vacuum Tubes Really Work
>>
>> Keith,
>>
>> Since it's loose from ground, and no corcuit can be made, it hangs in
>> space,
>> and can only be acted upon by the electron flow from the cathode.  
>> In this
>> case, if the grid is slightly more positive, it will accept some  
>> electrons
>> thus bringing it to 0 volts or slightly negative to ground. This  
>> is called
>> coming into equilibrium or equalling out. If the tube is not slightly
>> positive, it will not accept any electrons, and the electron flow  
>> will be
>> opposed by the grid. Terman, and I think the author of Tubes 201  
>> discuss
>> this. In any case, the grid can never be made positive by these  
>> actions
>> taking place.
>>
>> Earlier, when Rich mentioned about grids, I thought he meant a grid
>> becoming
>> positive. Bill posted what he meant which is correct and the same  
>> as above.
>> I privately told Rich of this, and am sorry I questioned him, it  
>> was a
>> mis-understanding. We actually were meaning the same thing at the  
>> time.
>> Rich
>> like me does not believe a grid can become positive by being  
>> bombarded by
>> electrons. Even if a grid gets to the point of emitting electrons  
>> from
>> being
>> hot, they are replaced by the electron flow from the cathode. By  
>> reading
>> some other texts, none of those do either.
>>
>> Best,
>>
>> Will
>>
>> *********** REPLY SEPARATOR  ***********
>>
>> On 7/24/06 at 9:15 PM Keith Dutson wrote:
>>
>>> I am totally lost on this excessive grid current discussion.  If  
>>> there
>>> is a resistor or fuse tied between the grid and chassis and it  
>>> blows,
>>> the grid obviously has a potential above or below ground.  Which  
>>> is it?
>>> Can it be either depending on the fault?
>>>
>>> 73, Keith NM5G
>> [snip]
>>
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R L MEASURES, AG6K. 805-386-3734
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