[Amps] setting the grid adrift

[Will Matney]

I wish someone would answer a question I put out a few days back on this. How can a grid, connected to ground mind you, have a positive potential? Where would the charge on any gird go when connected to ground?

What is there to cause any charge to the grid? What are their polarity?

This brings the question of a floating gird, if it's not connected to anything, what happens at the grid? We all know the tube itself will start to act like a diode with high anode current, that's not the question. What will the grid do while floating there un-connected?

Last, if ions were to cause a grid to go into some emission, when the electrons leave the grid towards the anode, what's happening between the grid to the cathode? Keep in mind that the grid will have less electrons than before from emission, and electrons are still flying past it. Would the grid repel those electrons going by it? This grid is also connected to ground or 0 Vdc.

I'll let others figure this out.

Best,

Will

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

On 7/25/06 at 9:26 AM Chris Howard wrote:

>> If you read the actual TEXT from Terman, he states the grid 
>> will become positive.
>> 
>> Linky for you to tread:
>> 
>> http://www.w8ji.com/images/Amplifier/Bias%20and%20grid%20fuse/Terman.jpg
>> 
>
>
>Now that's an interesting piece of information, (And I note that
>Will posted the same passage recently).
>
>I have to object slightly to your assertion that the grid "will"
>become positive.  The paragraph in question seems to assume a certain
>condition of gas/ions/etc. to make it happen this way.
>
>Thanks very much for scanning the text of Terman's and Giocoletto's!
>
>Here's my latest newbie thoughts... just so you all can ride along
>with me on my educational trip...
>
>>From what I gather, loosing the grid from ground is not something
>you want to do in the course of normal operation.  As a fault condition
>it may or may not cause other things to happen.  And that makes
>sense... the grid is your method of control, cut it loose and you
>no longer have control.  It could float around near ground potential.
>It could head straight for plate potential.  
>
>Here is the conclusion I'm coming too:
>
>Setting the grid adrift, if done in a system where there are other
>controls on plate overcurrent, doesn't mean certain doom.
>And there are some conditions where it might make sense, it seems to
>have a higher sensitivity to certain kinds of faults that otherwise 
>require more sophisticated detection methods (speculation).
>And to me there is some engineering beauty to the idea of cutting off
>the element that is suffering... everything everyone has quoted so far
>seems to agree that loosing the grid will stop grid overcurrent.
>But you then no longer have a working system so you might as well
>shutdown HV and do a complete reset.
>
>It's just another fault-control tool in the toolbox.
>So whether or not you want to kill faults using that tool or some
>combination of other tools is a design issue, not a moral one.
>
>Am I getting there?
>
>Chris
>
>
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