[Amps] Grid fuses (was: Life and gain of 3-500Z)

[Bill Turner]

ORIGINAL MESSAGE:

On Thu, 20 Jul 2006 07:16:18 -0700, you wrote:


>If the tube is not gassy, and the grid is floating, the electron  
>stream from the cathode probably raises the grid-cathode (fil-CT)  
>potential to a few volts negative.

------------ REPLY SEPARATOR ------------

I have observed this phenomenon in small receiving tubes with the grid
floating. No doubt it applies to their big brothers as well. 

My understanding is the grid accumulates electrons from either the
space charge surrounding the cathode or the cathode-anode electron
stream and has no way of getting rid of them. Thus the grid becomes
negatively charged to a small extent. This negative charge repels
additional electrons from accumulating and a balance is achieved.

Willing to stand corrected if necessary. 

Bill, W6WRT