[codefox1]

Well, if you are doing real old, not so old, and pretty much to the end of the tube era, a Hickok would be great. I have a 533 Hickok , and also a simple Superior which does most compactrons/noval. There are also Knight/Eico/whatever that do basic testing pretty good too. Well many well respected opinions abound!

I like to test tubes in a set when I get it, just to see if there is any immediate peril like shorts or open filaments. Beyond that, the proof is whether the tube performs as expected in the set.