Tubes Tested on a Hickok TV-7A/U Mutual Conductance Tester.
The Tubes Test as Follows (Triode/Triode):
TV-7 Minimum for 6GM8 Tubes: 32/32.
The Minimum is Defined when the Tube has 65% of it's life left.
TV-7A/U was Rebuilt & Calibrated by Dan Nelson in May 2021.