1964 Zenith 5111 comes to life!

[DaveWM]

the easiest way is to use an adapter that plugs into the HOT socket, and the tub plug into it, there are two leads that come out, you connect a milliamp meter there (bypassed with a 1uf cap). use an analog meter. some folks use these in the audio world to check the bias setting of output tube.

Or you could disconnect the jumper wire that is used to connect the cathode to the chassis and insert the meter in series there, again use a bypass cap and analog meter.