• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Doubts on cathode stripping in tubes

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Indirectly, this the rationale for using hydrogen/deuterium as fill gas in HV, high power thyratrons. The lower mass/charge ion has less of a tendency to blow hell out of the large area, high emissivity cathode surfaces needed for a good high power thyratron. Xenon, neon, and mercury fills are used for lower operating voltages.
 
There are cases of cathode stripping during start-up of receiving tubes where the Heaters are "floating" on a DC voltage derived from the B+...
The damage occurs due to the Heater to Cathode voltage is greatly exceed for a short time before the B+ pulls down to it's loaded state.... Very repeatable....you can hear the clicking sound of the arc..
Simple fix is to put a protection zener on the voltage divider ...this way the zener clamps only during start-up, preventing an over-voltage on the Heater...
Problem 100% solved ...
 
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