17-10-2015, 04:11 PM
With a dual variable 30V dc psu you can do both heater supply (dc is fine) and grid bias. With separate grid bias cathode does go straight to 0V. If you then measure Ia mA at plus and minus half a volt on nominal grid volts, the difference in the two Ia readings will be the transconductance in mA per volt.
That will give a pretty good idea of whether the valve is OK or not.
That will give a pretty good idea of whether the valve is OK or not.
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......O...Chris....O
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......O...Chris....O
