[Dick Finn]

It really depends on what you are looking to measure. Volt meters have three major categories of settins. AC Volts (Alternating current like you see in your wall socket), DC Volts (Direct Current like you would get off a battery or would see in a circuit where the current has been rectified --or converted to direct current from AC) and Ohms (resistance). As a rule of thumb, set the meter at a high range before inserting the probes. Turn the settings down until you get a reading.

Quite honestly, a tube type radiois a dangerous place to be putting your fingers if you don't understand enough about electricity to operate a volt meter. You should probably do some reading about electronics before venturing forward.