ONE Sylvania 6B4G vacuum tube in box 1952 date code F2M Black Plates / dual flat plate Hanging filament D getter TUBE 1 = 6600 micromhos @ 90mA plate current Tested on Triplett 3444 where 2200 is pass/fail. Bogey NOS values for 6B4 = 5250 micromhos / 60 mA plate current NO SHORTS / NO GAS tested at 250v plate / 250v screen
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