A calibration tube (a special selected 6L6) was once available from Hickok to verify that your tube tester was giving the correct Gm (micromho) reading. All 6L6 tubes are not usable for such a test tube. Only about 1 in 3 tubes that test good under standard tests are suitable to create a calibration tube. There are other tests and conditions that must also be met. The calibration test tube I offer has met all necessary conditions. After selecting such a tube (used tubes are best because a tube that has been burned in is more stable). After selecting and testing, I note the gm reading on a label that I apply to the tube. I check my tester each time I make one of these tubes with my calibration standard to maintain accuracy. I offer two such tubes, one for the Hickok 532 through 6000 series (excluding the 539) and the second for the 539 series. These tubes should not be used to play around with to attempt to get your tube tester to read the same as the calibration tube but only placed in your tester for verification after all the proper service, repairs and tests have been performed and your tester has been verified to be functioning properly. Even when all is correct, there can be small differences (as much as 2 - 4 graticules) in the gm readings between the same model Hickok testers. Although Hickok testers are considered to be the best by most of us, none of those that were made for the service industry are precision or laboratory instruments and some variations in readings will occur. Although the 532 - 6000 test tube may be used as a general purpose test tube, there is no such thing as an accurate, all around general purpose calibration tube. If the calibration test tube is used on non Hickok testers or other Hickok models not included in the models listed, the readings may be different. The tubes I offer are made for Hickok testers to be used in the Hickok models they are intended for. The tube's readings may be altered depending on the bias, plate and filament voltage that is applied to the tube. They should not be used in an emission checker. If you are going to use one as a general purpose test tube (such as a non Hickok mutual conductance tester), have one just for this purpose. Don't use a calibration tube that was made for a particular Hickok model and expect the reading to be remain accurate if you also use it in a tester other than the one it was made for. For more information, please refer to the information at the available web pages below:
http://www.radiolaguy.com/PDF_Files/Hickok%20539C%20Calibration%20V4.0.doc
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