My question is does anyone know the cathode voltage (not current) of (say) a 60W tube, relative to ground?
My reason for asking is that if I was designing a high-power tube-type RF amplifier, the cathode return would be "clamped" at some voltage higher than the normal operating voltage for safety reasons. For example, if the meter movement opens, a wire breaks etc.
I don't know enough about the physics of CO2 glass laser tubes and power supplies to know how that works. If it's just a volt or two, I can use two back-to-back strings of high power diodes (like 6A10's) to make sure the voltage of the cathode circuit at the meter never exceeds the sum of the forward voltage drops of the diodes against ground. If it's less than 50V or so, I have 50W zener diodes in my parts box as well. (used to set the cathode bias of triode power tubes, in case anyone is interested.
![Smile :-)](./images/smilies/icon_e_smile.gif)
I haven't seen this done in laser engravers, but it's standard practice in radio transmitter designs to protect the operator from high voltage appearing on the panel meters in the case of a circuit fault.
Thanks,
--jim