While Peter's reference to the Eimac article is excellent, I just want to
report that there has been some reports by users that it might be possible to
use the 4CX250 series of tubes in a ground-grid arrangement without a screen
voltage. The control grid on this tube is extremely sensitive and easily
destroyed, so the "normal" grounded grid connections will destroy it. A few
ham have experimented with grounding the screen grid and connecting the control
grid either to the cathode or through a large resistor to the screen.
I only mention this because hams are experimenters. I have seen such circuits
and claims that they work, but no hard documentation. I would not use a tube
in such a circuit unless I was prepared to test and monitor the actual power
dissipated by the grids to verify they are within limits - and that the total
operation is desireable.
Over the years, I have seen at least two articles on using the tube in this
manner. I am not recommending this circuit nor vouching for it. Similar
arrangments, with other tubes, are used in modulators and audio amplifiers -
but just because a circuit appears in print does not mean it is good.
73, Colin K7FM
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|