03-04-2018, 08:28 AM
There is an internal adjustment and if you do a search online for the calibration instructions you should be good. What I am saying is set the tester up to test a tube, insert the tube and let it warm up. Then press the line button and adjust it to bring the meter to the center point and then check your voltage, it should be close. If its not then you will have to trouble shoot or at least run a calibration on the unit.
Gregb
Gregb