Re: [Amps] filament supply options

[Don Havlicek <n8de@thepoint.net>]

I believe you meant to say:

"Hot-R is 8.3 times as much as Cold-R"

If the Cold-R is ONE TIME LESS than the Hot-R, the Cold-R is ZERO ....

I also 'cringe' when I hear advertising using "5 times more" .... that 
means SIX TIMES as much ... [one time more is twice as much!]

The mathematician in me 'gridleaks' out.....

Don
N8DE


R.Measures wrote:
> 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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