[Amps] filament supply options

[R.Measures]

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=20=

> and never light up the tube

=F0  Good point, Jeff.  The cold-R of a 3-500Z is 8.3x less than the=20
hot-R.

> - Add some series resistance to limit surge current when cold...For=20
> example, a 6V supply with 1V of drop across the RF choke
> - Alternatively could arrange a soft start circuit to ramp the voltage=20=

> and minimize cold current.
> - With DC on the filament, the Grid to cathode bias varies along the=20=

> filament the same way, which causes more emission from one end of the=20=

> cathode than the other.  Some people talk about reversing the filament=20=

> connections periodically to even out the wear.
> - Very easy to adjust filament voltage lower for better life at your=20=

> emission needs.
>
> jeff, wa1hco
> ...
>
>
Richard L. Measures, AG6K, 805.386.3734.  www.somis.org