On Mon, 16 Apr 2001 04:36:23 -0700 measures <2@vc.net> writes:
>When the screen arcs to the anode, and the SCR has not yet fired, we
have
>several kV on one end of the 2-ohm R. My thought is that c. 1500A
>might damage the gate.
>
>cheers, Marv
>\
>thanks
>>
>>
Good Morning Rich,
True, 1500A would not make for a happy gate... but, that is not the
case here.
I'm guessing to arrive at that figure you have de-installed the glitch
R, assumed some perfect power supply filter caps with no ESR, ignored the
inductance in the plate circuit (including the plate RFC) and ignored the
screen supply bypass capacitor... etc.
In the real world, the glitch risetime will be sufficient to allow the
SCR to trigger (in 2uS or so) thus protecting its own gate as well as the
zener string and the screen socket cap.
In the other world, you could still lilkely protect the screen
circuitry by upgrading to a 100A fast SCR. Of course, this arrangement
guarantees to disintegrate the screen itself....
The idea here is to protect a zener string screen regulator (and the
tube socket bypass cap as a bonus)... not to replace any other protection
circuitry.
73,
Marv WC6W
*
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