VTTC grid leak

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


Hi fellow VTTC coilers,

Having built some well functioning VTTCs, I still am doubting that I
understand the grid leak circuit correctly  ;-)

In the archives I found differing opinions. It is agreed on that "As
voltage is applied to the plate first, the tube conductes and the
tank circuit is pinged, transferring energy to the grid coil."

But then:
Version A): The grid coil sends some *positive* voltage to the grid,
turning the tube further ON. The grid draws some current, which
develops a voltage drop across the grid leak resistor. It is stored
in the grid leak capacitor and builds up to form a negative bias
voltage, which cuts the tube OFF. Grid voltage swings from negative
to positive voltage.

Version B):  The grid coil sends a strong *negative* pulse to the
grid, which turns the tube OFF. The negative charge is stored in the
grid leak capacitor. Grid voltage swings from negative to zero
voltage (GND).

For both versions the story continues:
"Eventually the grid leak resistor bleeds off the charge of the grid
leak cap and the tube conducts again."

Tending towards version A), I really would like to understand the
mode of operation.

Bye		Herwig