Most designs for GG amplifiers show a relay in the cathode circuit to
switch the tube from standby to operate and there is usually a
resistor across the contacts, typically 10K or so.
Is this resistor really necessary? With it present, the tube would
never go totally into cutoff. With it out, it would. Why is that
important? Many older low power rigs (6146 etc) have the key directly
in the cathode circuit with no apparent problems. With an 8877 for
example, wouldn't the cathode voltage simply rise to the cutoff point
and stay there? I have the cathode tied to the heater at the socket,
so cathode-heater voltage differential wouldn't be a problem. The
heater transformer insulation is rated at 535 working volts, so as
long as the cutoff voltage is less, that shouldn't be a problem
either.
Any comments?
73, Bill W7TI
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