National Union NU Number / Type 80 #80 Vacuum Tube Rectifier Black Plate ST Shoulder Shape June 16 2025 came from an excellent lot

came from an excellent lot and should work fine

GM-BRANDED 6SK7 tested as good on our Paul Hart-calibrated TV7/U

They have double O getters

This historical recording sounds pretty good

Transconductance measured (From left to right): 42

National Union NU Number / Type 80 #80 Vacuum Tube Rectifier Black Plate ST Shoulder Shape June 16 2025 came from an excellent lotThis National Union number 80 rectifier tube was tested on our Paul Hart calibrated TV7 U for shorts, gas and emissions. There were no shorts or gas. It measured 47 50 where minimum (65%) is 40 40 and 100% is 62 62. WE HAVE SCORES OF THOUSANDS OF VACUUM TUBES. IF IT'S NOT LISTED, WE MAY HAVE IT. PLEASE ALSO SEE OUT ETSY SISTER SITE "LOWTECHTWOO" AND OR CALL OR TEXT US AT 202 372 6931 IF YOU DO NOT SEE WHAT YOU NEED OR HAVE ANY QUESTIONS. 1. MOST FORMS