I have had good luck with a Jackson 648A tester. It is not an expensive Hickok mutual conductance tester. It uses a "Dynamic" testing circuit and there is much debate if that is really better than simple emission testing. But it does have a test I have found useful. It has a “Life Line Indicator” test which reduces the filament voltage. It sounds like a gimmick but it seems to work for me. Just last month I had a weak 12AX7 in my T-4XC. It tested good in the regular test, but it was bad in the life test. I replaced the tube and now I don’t have to turn the gain so high to tune up. That test has also worked for me with other tubes.
That life test has also been useful for 6JB6’s. It has found soft tubes with the life test that otherwise have tested good. Whether it finds all soft tubes is a question, but it has proven to be a good screener by finding tubes for me that have tested to be soft in my T-4XC (I had a box of unknown tubes). But swapping tubes is by far the best test but at least I can eliminate the "no chance" ones. My Jackson 648A did not come with the 9-pin NOVAR socket needed for 6JB6’s. I added it myself and it was not hard to do using the schematic. One advantage for the Jackson 648 is that Vacuum Tubes Inc. publishes their own manual for it (I have no connection to this company except as a customer). There is an excellent discussion of tube testers at http://www.tone-lizard.com/Tube_Testers.html It is written from an audiophile’s point of view, the only other group still using tubes. 73, Bob WW3QB --- On Sat, 1/30/10, Richard Palmer <[email protected]> wrote: > From: Richard Palmer <[email protected]> > Subject: [Drakelist] What circa tube tester? > To: [email protected] > Date: Saturday, January 30, 2010, 9:03 PM > I hope this is not off topic. > With the use of "vintage" being used for all Drakes and tube > testers, many from the 1940's and before, up to the last > ones made, it has become impossible for me to determine what > will service my early TR-4. > > I have spent hours and hours looking up tube testers by > type, make and model. I have spent hours squinting at > pictures trying to count socket pins. I am burnt out and am > looking for help in finding just where to look. I have no > idea if post WWII testers even test 9 pins, or if all 7 pins > are of the same size. > > Richard Palmer > KB8NXO > > -- The law, in its majestic equality, forbids the rich as > well as the poor to sleep under bridges, to beg in the > streets, and to steal bread. - Anatole > France > > > _______________________________________________ > Drakelist mailing list > [email protected] > http://mailman.zerobeat.net/mailman/listinfo/drakelist > _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
