Happy day, finally found my TV7DU while unpacking many boxes

[wa2ise]

Had about a hundred moving boxes to unpack, found stuff I'd forgotten I had, but couldn't seem to find the TV7DU mil spec tube tester I knew I did have. But today found it in a box I had labeled "TV7DU", DUH!
This tester is a Gm tester, which runs the tube in a circuit that somewhat simulates that in an actual TV, radio, or audio amp.

Some time ago I did find my emissions tube tester. That one does compactrons, though. An emissions tester just sees if the cathode can still emit the specified amount of electrons. Usually, that's good enough, as it's usually the cathode "running out of electrons" that causes tubes to go dead.