[Amps] Life on the Screen?

[R.Measures]

>
>  The Collins 30S-1 (4CX1000A), and several larger commercial amps
>(4CX5000, 4cx10000) for which I have schematics, incorporate a loading
>sensor which has a (capacitive) voltage divider with one end connected
>directly to the plate.  These units also all happen to connect the screen
>directly to ground.
>
>  The Collins 30L-1 (811A's x4) uses the Plate-Grid capacitance of one of
>the tubes along with smaller than typical grid bypass caps plus a small
>RFC back the the grid return to implement this same type of divider.  
>
>  Two questions:
>    Could the Plate-Screen capacitance of a Tetrode (4CX250, 4CX1000A,
>etc.) be employed in a similar fashion if the screen was bypassed with an
>appropriate value capacitor.
>
**  If the screen is bypassed, there is no signal potential on the screen 
- and it can not be used for such.  Unless a grid-driven 4cx5k or 4cx10k 
has their internal feedback-C  neutralized, they will not be very stable. 
 I've been there, and it cost me some hair.  

>     and...
>
>    Would the resulting signal be exactly in phase with the Plate voltage
>so it could additionally be used in a phase discriminator style tuning
>indicator?
>
**  The slam-dunk tuning-indicator  for an grid driven AB1-tetrode is the 
screen-I meter.  Once the ZSAC is adjusted, and the max grid-current is 
almost zero, the Screen-I meter tells us everything we need to know.  

cheerz, Marv.