Matched Pair General Electric GE 6K6 6K6GT Vacuum Tubes Black Glass NOS-Testing Changed The World They tested (from left to

They tested (from left to right) as follows: 52 and 55 where minimum (65%) is 40 and 100% is 62

new in box GE 2D21 tubes tested to spec on our TV7

This perfectly-matched septet of new old stock-testing Sylvania 7A7 tubes was tested on our Hickok 800 for shorts

The GM-LABELED ones all have 312 Sylvania EIA codes

This is a mid-60s

Matched Pair General Electric GE 6K6 6K6GT Vacuum Tubes Black Glass NOS-Testing Changed The World They tested (from left toThis matched pair of GE 6K6 6K6GT tubes was tested on our Maxi Matcher 2 with 325 volts on the plates and a bias of 36 volts for shorts, gas, plate current and transconductance. There were no shorts or gas. Tube One measured 1900 micromhos, 27 milliamps' plate current. Tube Two measured 1850 28. New nominal is within one standard deviation of 1900. These tubes have copper support rods; rectangular mica spacers; black and silver bottles and 2 22 188 5