Matched Pair Sylvania 7C5 Vacuum Tubes Gray Glass 6P14 This variety has black

This variety has black

new in box RCA 7A8 tube tested to spec on our Paul Hart-calibrated TV7/U

These five GE 6SF7 tubes were tested on our Paul Hart-calibrated TV7/U for shorts

This new old stock-testing RCA Cunningham engraved base type 85 tube was tested on our Paul Hart-calibrated TV7/U for shorts

Matched Pair Sylvania 7C5 Vacuum Tubes Gray Glass 6P14 This variety has blackThis matched pair of Sylvania gray glass 7C5 tubes was tested on our Maxi Matcher 2 with 400 volts on the plates and a bias of 36 volt for shorts, gas and transconductance. There were no shorts or gas. Transconductance measured 2340 micromhos with a plate current draw of 24. 5 milliamps for Tube One and 2070 25. 2 for Tube Two. (New US made 7C5s typically test with plate current from the mid teens to mid 30s with transconductance from 2300 micromhos