A secondary issue on the filament transformer grounding/ungrounding:
When the transformer secondary is floating, it then becomes important that
the transformer primary to secondary breakdown voltage is greater than the
plate voltage in case of a plate to ground arc/flashover (remember the grid
is
grounded). If the grid meter circuit blows open, the full plate voltage can
appear on the cathode/filament circuit.
A couple of really robust back to back diodes can protect the grid meter but
they have to be there to do it. Also, does anyone have info on how quickly
large diodes will conduct in a flashover scenario? Seems that the rise time
could be a problem but I am not sure about that.
73,
Gerald K5GW
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