Steve,
As the grid leak resistance gets lower, the tube will run hotter and less efficiently.
The will conduct for a larger portion of the RF cycle. I forget what grid resistance
I used on my coils. It was probably about 2800 ohms, but at times I used 5k ohms.
I forget if you're using staccato. If so, then the tube will run cool despite a low
grid resistance. In my coils without staccato, if I went too low on the grid resistance,
then the tube would run too red at max spark length. So it was a compromise
between max spark length with acceptable plate redness (orange red with
23" sparks). Of course at lower pulse rate the tube will not get red.
John
-----Original Message-----
From: Steve White <steve.white1@xxxxxxxxx>
To: Tesla Coil List <tesla@xxxxxxxxxx>
Sent: Mon, Feb 26, 2018 6:56 am
Subject: [TCML] 833A VTTC grid leak resistor
My 883A VTTC is based on Steve Ward's schematic. His schematic indicates a 5K ohm grid leak resistor. With that value I was getting a 19" spark at 140 volts on the variac. Today I experimented with the grid leak resistor by cutting it in half to 2500 ohms. My spark length increased by about 1" to 20 ". I didn't want to go any smaller yet. Is there a value of grid leak resistor that is too small for this design?
Steve
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