Tube manufacturers & suppliers
Simple Tube emission test
- A tube with low electron emission from the cathode performs in general unsatisfactorily,
especially in some critical circuits. A simple method to check emission consists in applying an AC
voltage (at 50 or 60 Hz) between the cathode and all the other electrodes tied together (for
example in a triode one should connect together the grid and the plate) and
measuring the DC current. That gives a relative indication of the emission. An emission test
must be short to avoid damaging the tube (3 seconds is the maximum recommended).
This table gives the voltage and current values for a number of tubes.
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