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In general terms, CRT are tested as triodes. On B/W CRT this means there are five connections, two Heater, Cathode, Grid and First Anode or Grid2.
Color CRT have three guns vs. the single B/W tubes, color heaters share the same connection. There is either a switch to select between the three guns and a single meter or three meters to test the three guns at the same time.
To test for leakage or shorts, various voltages are connected to the elements and any current above a small amount usually lights a neon lamp.
Heater voltages range from about 2.34 V to 12.6 V. Anode voltages range from 30 V to 300 V. These voltages depend on tube type. The cathode current is displayed on the meter for the emission test and the actual current would be indicated good if something around 0.3 ma. or more. Only about 1.5 ma. may be the maximum on the meter.
Cutoff is measured by putting a variable negative voltage on the Grid to reduce the emission down to a certain point.
Clearing shorts is done by charging a capacitor and then discharging the capacitor across the shorted elements.
Various methods are used to "restore" emission, some of them riskier than others. There are different ideas of what works best. Methods range from temporarily boosting the heater voltage a certain amount, and/or increasing the anode voltage, also sometimes using a charged capacitor to provide a pulse of high voltage and current.
You really need to analyze the schematic to figure out the details of a particular tester. Some manuals explain more then others.
This is meant to be a general overview, your mileage may vary.
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