VTTC with 4-125 tube

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: herwig.roscher-at-gmx.de 


Hi VTTC coilers,

I am trying to audio modulate a 4-125 tube. As I was not satisfied
with the audio quality from control grid modulation, I am using
screen grid modulation now. Plate voltage is 2500 V and screen grid
voltage is 175 V +- 175 V (i.e. the screen grid swings between 0 V
and 350 V). To my surprise there is an oscillation with V p applied
but without V g2 (i.e. g2 tied to GND).

Is the influence of the screen grid of transmitting tubes on I p so
small (tubes used in radios cut off any I p if there is no V g2) ?

Cheers,

Herwig




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