*New Updated 2026 Version with Way More Info*

One 6L6 that has been marked with its µmhos (umhos / micromhos) values to be used in calibrating tube testers that have a µmhos readout on their dial.  This tube has been calibrated using a known good laboratory grade tube tester serviced and calibrated by a professional.  It is also then double checked using a modern computerized & calibrated tube tester.  See pictures.

About the Tubes We Use:
  • Tube may be used (which is actually a good thing for calibration tubes)
  • Tube in picture are just representative, not the actual tube you will receive
  • We use brand name tubes such as RCA, Sylvania, Tung-Sol, etc. for making these sets
  • Typically the 6L6 is a metal tube, which are very good for this purpose
  • These tubes are tested for shorts / gas before calibration
  • Tubes are tested at 250v plate, -20v grid, with +/- 5% swing
Data Provided About The Tube (way more than most sellers provide):
  • Date Tested
  • µmhos calibration value
  • Plate Voltage value
  • Grid Voltage value
  • % Grid Swing (fed via AC signal)
  • Heater Voltage value
  • rp (ohms) plate resistance value vs. reference of 1700 ohms
  • ip (ma) plate current value vs. reference of 40ma
  • gm (µmhos) value vs. reference of 4700
  • mu (v/v) value vs reference of 8.0
A few common tube testers that have µmhos readout on their dials include:
  • Hickok 533A, 600, 600A, 800A, 800K, 605, 6000, 6000A, 539A, 539B, 539C, 752, 752A, 536, 750, etc.
  • Western Electric KS-15750
  • Heathkit TT-1
  • TV-3, TV-10, TV-2
  • Many More...

If you are looking to calibrate a TV-7 tube tester, please see my other auction for tubes marked specifically for them.

Unlike some other auctions suggest, you can not calibrate a TV7 with just one tube.

You will need to find the calibration instructions for your tube tester on-line and use them.  These tubes will ensure you have calibrated them correctly as they have been marked by a known recently calibrated tube tester.

Tube Tester NOT Included