rich wrote (>), and i offer my unsolicited thoughts, (for what
they're worth)
> At 6kV, for a ZSAC of 0.5A per anode, the grid bias requirement for a
> 3CX2500F3 (Mu=22) is roughly -220V. If the -220V bias supply is
> connected between the filament transformer CT (cathode) and
> chassis-ground, the grid flange can be directly grounded.
the thing i don't like about this sort of scheme is that the formerly
wimpy (grid) bias supply now must become a pretty big power supply
which will handle the full cathode current.
> // Another
> labor-saver with such tubes is to put the filament RFC in the primary of
> the filament transformer instead of the secondary. This allows one to
> use a 2A bifilar RFC instead of a 51A bifilar RFC. ..... The filament
> transformer is mounted on a sheet of insulating material, and the primary
> and secondary windings are RF-bypassed to the frame of the transformer.
> The measured C (typically 60pF) of the tranformer to chassis-ground
> figures in the C2 calculations for the tuned input.
neat! i've never tried this, but i'll file it away.
and my comments are meant to apply to legal - limit amplifiers for
the amateur bands. others are apparently building amps for other
applications.
73,
George T. Daughters, K6GT
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