[Electronic M]

One way to make a universal universal (as in should work on any tester and CRT) is to find a junk scope that uses the same base as a 10BP4 (and 90% of CRTs pre1960), Rob the base off the scope tube and populate clip leads onto the pins for the gun of a 10BP4. Nearly all testers had settings and socket to test a 10BP4 so if you build a socket that adapts that to clip leads that socket will adapt almost any tester to almost any CRT...It will only one gun at a time, and you'll have to label your clip leads and consult the pinout of the tube you want to test, but it sure beats having no adapter at all.

This is exactly the universal adapter I made when I decided I wanted one. I color coded my leads based on the color code for the red gun leads in a color CRT, and have a good enough handle on which of those are what element that I can hook them up to a monochrome the (which used a different color code than a color tube) if I know or can see the pinout through the glass. Most testers only need 2 H leads, a K, a G1, and a G2 to work.