The Power for the Model 257 is 110-120 Volt A.C.
The use of the model 257 can be tested on many tubes as such black and white picture tubes, color picture tubes and diodes.
If the “SHORT” indicator lamp illuminates continuously during the tube test, it indicates a short or leakage between cathode and heater or control grid.
While performing the quality test a tube is short, this should not be conducted in order to avoid damaging the tube tester.
The quality of the tube is assessed within working limits using the “Good ? Bad” scale after shorts check has been done to ensure there are none.
The device is able to test multi-sectioned tubes, it will just involve repeating the testing for each section which is specified in the tube chart.
Possible readings on the meter are such sections of green, which test good, red indicates bad, or indicators for diodes for those within the tube.