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A calibration tube,
a special selected 6L6 (more correctly referred to as a
calibration verification tube) 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 I test good
under standard tests are suitable because of an internal heater
imbalance. A second test for heater hum is also necessary. I
offer such a tube that I test, select and verify that each is
suitable for verification. After selecting such a tube (good, used
tubes are best because a tube that has been burned in is more
stable), I test them on a properly calibrated (and periodically
confirmed) tester type that the tube is to be used on and note the
gm reading on a label that I apply to the tube.
I presently offer
calibration verification test tubes for the Hickok 532 through 6000
series (excluding the 539 & 580), Military models I-177, TV-7 and
the 539B/C 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 and calibration procedures 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
on some *models)
in the gm readings between the same model Hickok testers. Although
Hickok testers are considered to be the best by many, none of those
that were made for the service industry are precision or laboratory
instruments.
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 in
testers or other than the models noted above, the readings are
likely to be different. The tube's readings depend on the
bias, plate, screen and filament voltage that is applied to the
tube and these differ among tube tester models and brands. 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 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 calibration information,
select:
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