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Registered Member #4953
Joined: Sat May 19 2012, 11:56PM
Location: Australia
Posts: 12
Hi Guys, first post here.
I'm building a Dual 811A VTTC based on Steve's FAQ (here) and I have a few questions about selecting the grid leak resistor. I currently have two 1K, 100W wirewound rheostats (pictured below) that I was going to connect in series, but I'm not sure if they will do.
1. Steve's schematic uses a 500R resistor, but most others out there use anywhere from 2K to 5K ohms. This is a big difference and I was wondering what's right for a dual 811A coil (with or without staccato, with or without voltage doubler on the MOT)?
2. I am worried about the inductance of the rheostats since they have a large diameter and large number of turns. Is this likely to cause problems, or will the Q be too low to worry about due to their resistance?
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
1. I am pretty sure 500 ohms is too low, I would say the optimal resistance for 2 tubes would be closer to 5k (10k for one, after all its a pretty small tube). 2. The inductance does not matter as the resistor sees neary DC voltage.
Registered Member #4953
Joined: Sat May 19 2012, 11:56PM
Location: Australia
Posts: 12
Thanks Doc,
I'll look into other solutions for the grid feedback resistor then because my rheostats will only be 2K max. Good to know that inductance isn't much of a concern.
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Choosing grid leak resistor for VTTC
