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Re: [Amps] filament supply options

To: jeff millar <wa1hco@adelphia.net>
Subject: Re: [Amps] filament supply options
From: R.Measures <r@somis.org>
Date: Sun, 25 Apr 2004 06:15:55 -0700
List-post: <mailto:amps@contesting.com>

On Apr 24, 2004, at 10:51 AM, jeff millar wrote:


Things to think about
- Cold resistance much lower than hot, PS may fold back on overcurrent and never light up the tube

 Good point, Jeff. The cold-R of a 3-500Z is 8.3x less than the hot-R.


- Add some series resistance to limit surge current when cold...For example, a 6V supply with 1V of drop across the RF choke
- Alternatively could arrange a soft start circuit to ramp the voltage and minimize cold current.
- With DC on the filament, the Grid to cathode bias varies along the filament the same way, which causes more emission from one end of the cathode than the other. Some people talk about reversing the filament connections periodically to even out the wear.
- Very easy to adjust filament voltage lower for better life at your emission needs.


jeff, wa1hco
...


Richard L. Measures, AG6K, 805.386.3734. www.somis.org

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