(1) Tested 1920s Gold Seal GSX-20 "Hy Mu" (High Gain) Triode Tube.
Please note that the this is NOT a type 20 tube. The '20' refers to the gain rating.
This is a very specialized and rare 6 volt resistance coupled high gain tube similar to a Daven MU-20 tube.
Early shaped glass envelope with the both original labels still present (front and back).
Since no known test settings exist for this particular tube it was tested with the settings for a type 40 tube with the filament setting at 6 volts and a bias of 32. This gives a general idea of its strength and condition but is far from perfectly accurate - see test results below.
Tested on a calibrated Hickok TV-10 military tube tester with no shorts and no leaks with the following results:
Gm Test = 575 micromhos
Minimum pass/good = 125
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