AVO Mk4 Curve Tracer Modification
This is weird. For instance you can see how the tube warms up, or what it does to change the heater voltage. This tells you quite something about the quality of the cathode. This might be offered as a modification to your AVO Mk4. I have not completely finished it yet. There will be two BNC connectors at the back of the AVO, and you can connect a standard Scope there to see the curve of the tube, in the actual working point you selected on the AVO. It works simultaniously to normal testing. So can right away check on the scope what you are doing.