Please note, the EML tubes are tested with the filament at DC voltage. This is done so for practical reasons in the factory. If you want to repeat the test, make sure you don't get stuck in the never ending confusion about the method. There is no 'Standard' method for DC testing. At EML we test the tubes with the heater grounded on one end, and the other end to a positive voltage. Then we bias the tube manually, and we measure the Control Grid Voltage needed. However this Control Grid Voltage is another as when measured with AC heating. The Control Grid Voltage we find with the DC method as we use it, is less negative by half the heater DC voltage. This doesn't change the validity of the test results, it is just when you want to repeat it, you have to do it the same way

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