Have a look at what he did in the video below. The tester is just a few resistors, a tube socket, and some bench power supplies. Of course, you may have to adapt it to whatever tube you are testing.

But how to know whether your find is any good? [Rob’s Fixit Shop] took a look at a tube tester, once a fairly ubiquitous item, but now a rare sight. To look at it’s a box with an array of tube ...