[Amps] filament supply options
Don Havlicek
n8de at thepoint.net
Mon Apr 26 07:04:22 EDT 2004
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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