[Electronic M]

There's 4 types of tester Heater only(useless unless you have a dead series string tube in a TV), Emissions (cheap and not great), in-between types (better than emissions, not as good as Mutual conductance), mutual conductance (usually expensive).

I think my B&K dynajet 606 is one of those in-between types that isn't expensive...It's main draw back is it doesn't test 1930s fat pin types...I work on radios too so I ended up getting a cheap emissions tester for those.

There are others out there that are decent and affordable. A tube tester isn't the last word on tube quality especially on sweep tubes and HV rectifiers (those you sometimes can only check by substitution.)