Matched Pair General Electric GE 6K6 6K6GT Vacuum Tubes Black Glass NOS-Testing Changed The World These two Philco 6U7 tubes

These two Philco 6U7 tubes were tested on our Paul Hart-calibrated TV7/U for shorts

respectively where new/nominal is within one standard deviation of 5000

Date Codes: 1-43 and NK

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

This is a mid-60s

Matched Pair General Electric GE 6K6 6K6GT Vacuum Tubes Black Glass NOS-Testing Changed The World These two Philco 6U7 tubesThis 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