In the best of all worlds, plug a variac into an isolation transformer and put the 10K resistor and a fused ma meter in series with the output. Set the Tester up as if for a 6L6 after allowing warm-up and setting the line voltage. Adjust to 5 ma. Multiply by 1000 to get micromhos. What is listed on this page is a means to verify calibration.
Adjustment varies by model and in some cases requires replacing resistors.
Nothing on this page requires removing the chassis from the case. Set fn sw to D, depress button 3. Cardomatics require special test cards.