Tubes Asylum Questions about tubes and gear that glows. FAQ

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There is some good news; but some bad as well...

Posted by Interstage Tranny (A) on January 19, 2012 at 15:34:53

In Reply to: hickok 600 tube tester conductance values posted by tubeflash on January 18, 2012 at 16:49:29:

The chart for that machine shows a new tube. However, the accuracy of the 600, 800, 6000, 8000 testers has problems. You see, the average machine of this series is known to be optimistic. For example, where the 12AX7 is concerned, a new tube should read 1250 uMhos. However, with this series, a new 12AX7/ECC83 will read about 1600 uMhos; even when calibrated. The 1250 on your machine will read lower on the top of the line Hickoks. This is a problem, especially when selling tubes using these 600 and newer testers.

The world reference tester is the Hickok 539B or C; as well as TV7 machines. A new 12AX7 will read 1250 on the 539; about 48-50 on the TV7. When I buy a 12AX7 from a seller using a 600 or 800, I must presume the wide tolerance and optimism with the later machines. I have been burned way too many times in the past. The usual scenario was buying a 1250 measured AX7 on your machine that only reads 900 on my 539, or 44-46 on my TV7.

So, Micromhos values are relative to each tester type. If we try a Heath TT-1 or TT-1A, a Tripplet or a Jackson transconductance tester, all highly regarded, the measurements can vary widely for a new tube on each of these machines. We must not only know the calibration is decent; we must refer to the top dog machines' measurements, in order to really know where our particular machine stands.

Checking on epay, there are many sellers using 600 and 800 machines. These folks have been warned and sometimes their feedback suffers because of their optimistic results. If you google and check some of the forums on tube testers, you will learn that the accuracy of certain testers is very questionable. The error ratio for the 600 and 800 is considered at least 15% which can mislead. The info from Noel Lee is well worth exploring. He created charts which are vital to many of us.

Now, knowing this, your 600 is still a good machine. If you plan to use it for selling, hook up with a fellow collector who has a "reference" tester. Testing well known, collectible tubes, compare and chart what yours does vs. what the reference tester does. This way, you can be more informed for your collecting and selling, as well as more informative when you do sell. Best Regards & ENJOY !!!

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