[Amps] Regulated filament current

[Steve Wright]

On 08/09/15 04:00,

David Lisney <g0fvt at hotmail.com> wrote:

> [....] in directly heated cathodes the temperature would rise as the anode current and drive rose. In the constant current example this would cause the filament voltage to further increase which is the opposite to some of the manufacturers suggestions. I believe for example that a 4CX250B with a nominally 6v heater should have the voltage reduced to 5.5v if you are giving the device a good "battering" close to it's maximum frequency and dissipation rating. A constant current supply would do quite the opposite.

And this is exactly the type of thing I was meaning in an earlier post. 
Sometimes, well-meant, and on-the-face-of-it very clever ideas end up
discovering the hard way that tube is cleverer!  Oh well..

Make things as simple as possible but no simpler - Einstein.


S