Vintage Tube Tester Teardown

[Mr. Carlson] has an old-style 1940-era radio tube tester, the kind that used to inhabit grocery and drug stores. It is in amazing condition and he was kind enough to tear it down for us. The tester is a Model X from the Radiotechnic Laboratory in Evanston Illinois and, like [Mr. Carlson], we were amused that one of the indicators on the device is a Ouija board-like “doubtful” reading. When it lights up, it looks amazing.

This is much older than the old “TV tube testers” we remember as a kid, but the idea is the same: you have a bad radio or TV with tubes in it, it is a fair bet that the problem is a tube. Even if you don’t know much about electronics, you can carefully remove the tubes, drive over to the drugstore, test your tubes and buy a replacement for any that are bad. Uniquely, this tester even had a speaker you could use to listen to the tube’s output while testing.

We miss the old wafer-style rotary switches. There isn’t much inside, but we were surprised to see one of the test sockets had absolutely no wires connected to it. Inside there is a vacuum tube rectifier which leads to the question of what happens to the tube tester if it, itself, has a bad tube.

We wonder if you could put this much high voltage next to consumers today. Probably not. But it was great to get a look inside a very old version of this once common device.

We saw a 1958 tester that used punch cards. If you have enough gear laying around, you don’t even need a dedicated tube tester.