[AMPS] Re: Response of Rich

[measures]

>Rich:
>
>I raised the question of increasing the screen voltage on a grounded grid
>tetrode - from zero to something less than the "normal" voltage.  

As I recall, you specified something on the order of 130v for a 1000v 
screen.  


>Your response was that "DAF circuits produce feculance".
>
Was this the only response you saw? 

>Your latest response is:
>
>"Did I not also point out that the power out with your stated screen
>potential was comparable to the power from the driver?."
>
>Your answer does not make sense.  Let us assume we have a normal grounded
>grid tetrode.  

ok

>Now, we break the screen lead to ground and insert a 1 volt
>regulated positive voltage upon the screen.  Will the power output drop to
>that of the driver?  

No.  Only the ZSAC changes.  

>What about 2 volts?  

The gain of g-g cathode-driven tetrode does not change as screen 
potential is increased.  

>As the screen voltage is
>increased, resting plate current will increase and at some point grid bias
>will have to be applied as the plate changes color from red to white.

Why increase screen potential if it only changes ZSAC.?
>
>In a grounded grid tetrode, the control grid current will be greater than
>the screen current.  

Apparently c. 25% of total grid current flows in the screen.  

>By raising the screen voltage above ground, control
>grid current will decrease.
>
>What sort of interesting curve do you have that shows that power output
>drops to the input power as soon as the screen voltage is raised above
>ground - yet will reappear as soon as the screen voltage is raised to the
>rated screen voltage.  

You seem to be confusing grounded screen grid-driven amplifiers with g-g 
amplifiers. 

>  That would be an inverted square, wouldn't it?

>The 4-400 is rated to have 100 ma of control grid current when used in
>grounded grid configuration.  

Not according to Eimac specs.  Are you making specs up?.  

> Are you saying that as soon as I lift the
>screen above ground  that any grid current will cause splatter?
>
The screen is never operated above RF ground, either in cathode driven or 
grid driven service.  
>Colin  K7FM
>
>


-  Rich..., 805.386.3734, www.vcnet.com/measures.  
end


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