I am learning radio theory fro the Markus book "Elements----". In the chapter of 2 AF amp he advises to check for the various voltages, for example, cathode, plate and grid voltages.

My question : When checking voltages, should the tube be connected or not?

Regards

M Khan

Hi

Yes, in most cases you need a tube in the socket. It draws current and will effect voltage readings.

I agree with Norm. Voltages are normally read "under load" so you get a true reading. Typically, voltages will go up when no current is being drawn. A good example is an automotive battery. The battery is said to be dead when it can't deliver enough energy to turn the starter and crank the engine. However, the radio and dome light will often work as they normally do and the voltage will read 12 volts. As soon as the starter load is applied, the voltage falls "under load" and the dome light will dim or go out. Therefore, it is important to take voltage readings under operating conditions.