Are you sure your 6B7 doesn't fit in the same socket as the 6A6? The 6A6 does have pins spaced farther apart but most tube testers have a socket designed for either 7 pin spacing.
: I have a 6B7 tube that has 7 pins. Both of my tube testers show a 6B7 on the roll chart however neither one of them has the proper sized socket to insert it into the tube tester! I have what I think are every adapter that came with one of the tube testers and none of them are the proper size. (Hickok 752) A 6A6 tube also has 7 pins but they are placed further apart and fit the tube tester correctly. I have to believe I am missing an adapter? Thanks