Re: Zero emission?
When there's nothing to loose.
For a start, run the heaters for a few hours with grid and cathode shorted, and no other external supply, re-test.
Then if no luck.
WITH NO HT USED.
Run the heaters at 150%
Apply + grid voltage, (current limit may be wise, say 50mA) 10-20volts and watch for grid current.
When/if current starts to flow as cathode wakes up, switch off heaters and allow to cool with +bias applied.
If nothing happens the valve is internally shot.
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