TAD Bias Master BM4

This model comes with 4 octal probes, but I ordered 2 noval probes as well so that I can set up EL84's as well as 6V6's and 6L6's etc.
WARNING! - There are no instructions! - If you don't know what you are doing, don't try to use this unless you have a friendly tech to show you. You can download them from the TAD site, only 2 sides of A4 folded into a leaflet. Very basic instructions.
The probes each contain a 1 ohm resistor in the cathode lead, so they are measuring total cathode current (anode + screen grid). Circuit schematic diagrams usually state a bias Voltage (e.g. -37Volts) rather than current. This is a good starting point, but then you need to find the valve manufacturer's specifications from their data sheets. Then you can balance up each side of the push-pull stage.
The readout on the unit is 00.0 mA to presumably 99.9 mA.
A "Chicken head" pointer knob selects each of the 4 individual valves, or the OFF position.
It's really simple and easy to use (as another reviewer has said) and you don't have any high voltage connections to make through a test meter. The real skill is knowing just where to set the current level, which is of course different for each and every valve type and can be slightly tweaked for your preferred sound.