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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: Filament bias posted by vetmedrobert@gmail.com on August 5, 2017 at 13:01:05:
Ale's curves suggest that with 150v plate, -5v and 145v plate-cathode you have 13mA.With HT of 380v you drop 230v across the pate resistor, and at 13mA that gives you a 17.7K resistor at 7W. My calculations!
I'd replace that resistor with something better like a plate choke or Ale's gyrator. Ale has all the values for 10y with his gyrator on his site.
At these values you could use a Hammond 126C interstage just as a plate choke - it's rated 15mA. I use this with a 2P29L at 15mA and it sounds fine. I prefer it as a plate choke with a 0.2uF Russian teflon coupling cap made up of 2 x 0.1 uF FT-2. It's a simple inexpensive solution if you don't want a gyrator. If you want to push the current higher than 15mA you can use the Hammond 126B rated 30mA.
I've attached my 2P29L circuit with the 126C to give you an idea. I really like it - Ale liked the 2P29L as well. Cheap as chips. You could keep your precious 10Ys for the outputs. I have a stash which are just accumulating value in my drawer.
Edits: 08/06/17 08/06/17 08/06/17
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Follow Ups
- Anode resistor value - andy evans 02:41:30 08/06/17 (1)
- RE: Anode resistor value - vetmedrobert@gmail.com 09:15:30 08/06/17 (0)
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