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

[Will Matney]

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
>
>-----Original Message-----
>From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
>Behalf Of Will Matney
>Sent: Monday, July 24, 2006 8:59 PM
>To: amps at contesting.com
>Subject: Re: [Amps] "Tubes 201" - How Vacuum Tubes Really Work
>
>Tom, are you saying Terman was lying in the 1st edition of his handbook? I
>don't need to re-write anything, I have it here in print. I have a
>question,
>how can an element being bombarded by or gaining electrons be positive
>(over
>0 V, +0.1 volt DC or greater)? Is Termans satements about equilibrium hog
>wash?
>
>Best,
>
>Will
>
>*********** REPLY SEPARATOR  ***********
>
>On 7/24/06 at 9:23 PM Tom W8JI wrote:
>
>>>>Will wrote:
>>> That's slightly re-worded from my edition as he never mentions 
>>> positive.
>>
>>I have a later edition. Later editions almost always have improvements.
>>
>>> However, what he's meaning about positive, and he aludes to this in 
>>> other parts of the chapter, is really the grid being less negative or 
>>> more positive as compared to another element, so it will accept 
>>> electrons.
>>
>>You should rewrite his text then if you know what he meant to say.
>>
>>73 Tom
>>
>>
>>
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