On 08/09/15 04:00,
David Lisney <g0fvt@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
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