This little baby not only tests tubes but it allows you to match them, I also use a Tektronix 576 curve tracer to match tubes as well. The only solid state device that comes close is a MOSFET
I haven’t forgotten the importance of tubes. In the spring of 1964, March, I think, I layed on the living room floor carpet listening to Dad’s new Magnavox stereo as the reports of the Alaskan Earthquake of 1964 rolled-in on KCBS, San Fran . I was mesmerized. There are very few things electronically nowadays that mesmerize me. Lsying on the carpet in July 1969 it was a Moon landing, and at the same time being unsettled my a minor Bay Area earthquake.