DISCARD TUBES THAT MAY BE GOOD. A PROPERLY CALIBRATED CHECKER IS A
Many if not most of the vintage tube testers being sold as calibrated.....ARE NOT! I say this because there's a very important part of the calibration procedure that is almost always overlooked.
The reason this adjustment is not done is because it is omitted in what little calibration procedures there exist. Even the most detailed procedures I've seen in the Hickok calibration procedures omits this adjustment.
I have serviced, calibrated and sold a fair number of tube testers over the last 15 years and have yet to find one with this overlooked adjustment properly set. This means that if you are using a tube tester that has not been thoroughly calibrated..............you may be discarding good tubes.
My tube tester service includes a good cleaning inside and out, replacing any paper capacitors and any resistors that are out of Torrance. I clean and test all the sockets, controls and switches and of course, the tubes used internally. I check the meter for smooth, stick free operation and make sure the roll chart works as it should (its normal to experience some backlash one some of the late edition Hickok charts to because of their extended length).
Finally I perform the calibration and then test a variety of tubes with known values to complete the service before posting for sale.
If you are technical person with a unit in question or
one who sells & calibrates tube checkers, contact and I'll be glad to
share this info. This overlooked adjustment, is not always a simple
procedure on most tube checkers. Most require a component change rather than
make a simple adjustment.
First, I clean the piece inside and out, not just a quick wipe off of the obvious, but a thorough cleaning. I remove the knobs, clean and shine 'em if they are dull, clean the panel as best possible even in the hidden corners. Do the same to the under side and the inside of the case. I also clean the crud that collects under the knobs! Then comes the technical stuff:
1. Check the meter
movement to make sure it doesn't stick or hang up.
There are other little detail items I do that are too numerous to make a point of, I do all I can to make sure you get a tube tester you can depend on to perform as it was designed.
The cleaning and restoration performed does not always end up in a product that will look like new, but you will get a unit that is clean inside and out and will perform like new. Many of the old units were beat up pretty badly and came from shops that were not very sanitary. So regardless of the wear and tear I promise to clean them completely and before offering for sale, they will work properly. This I guarantee.
6L6 calibration tube, for use when calibrating your Mutual Conductance tube tester
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