Re: VTTC with 4-125 tube

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

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



Wim Bosma <wbosma-at-stud.tue.nl>  wrote:
 > A 4-125 (same as QB3/300)  will draw anode current with its screen at
 > 0 Volts if the control grid is not negative enough.

Hi Willem,

With the screen grid tied to GND and the mentioned small brush
existing, I measured the control grid voltage to swing between -250 V
and +180 V.

 > From your description of a brush discharge without screen voltage I
 > concluded that your circuit is unneutralized
You are right.

So, the cure should be varying the number of grid coil turns and/or
trying neutralisation.

Greetings,

Herwig



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