I have bought from 4 different well respected vendors and they all have the same test numbers of 14 - 19.5ma for their NOS listings. I don't know how to test tubes, so I just trust the sellers I have been using and have success with for years.
I use two 539C Hickok testers, both with digital to check a few measurements. I have also compared my measurements to other known tube sellers that have a good reputation and use calibrated testers and they fall in line with what I get. Plate current will vary with how much voltage is applied but if measuring as the standard was set up, they should all be close (tube testers). I trust my measurements after years of doing this and knowing that my two testers, besides other I have that are also calibrated, match up, within a few percentage gives me all the confidence I need. Those are some very high numbers.
Interesting and thanks for the info. I trust you over any dealer I have dealt with.
Also I have found that even though there set standards for how the 7193 facility of tubes is supposed to measure, within parameters (%), they can still vary a lot from one manufacturer to another. The E 1148 tube measures really low and they are supposed to be made to the standard but they set them up a little different. They still work fine in circuitry but if you are familiar with them, you might think they aren't any good or used. But I have tested many NOS and they all test in the same area. Tubes measuring 19mA with others from the same manufacturer and the same period measure quite a bit lower, well I don't know then. It depends upon the voltage applied etc. There are many variable, which is why it is nice to have a good tube tester and to understand what it is telling you.
Yes, they tend to go hand in hand. :^) And then calibration and the tester but I find that if everything is set up correctly, current and even mutual conductance tends to show within X amount of %, the same.
But who is testing that testers?)
I don't know what you mean. When you calibrate, you are testing voltage and current draw at many points as well as making sure certain resistors and capacitors are within specs. You then use tubes used for calibration that have a set value that is noted on them. The tester that is used to check tubes to be used for calibrating is set to very high standards. With my two Hickok 539C testers, both being calibrated, they test almost identical with calibration tubes and then with tubes being tested.
Well, but why people asking “is it possible”? If tubes are matched, it’s easy to check. Otherwise you can’t be sure, unless you did it by yourself. IMHO.
There are tube sellers that do a reliable job. I have bought tubes from Upscale audio and their matching, which I check, is right on. Some sellers on eBay, I have no idea but some of the testers they use are ones I would never use.
You state that you test at 150 volts, and you seem to be implying that testing at higher voltages would produce higher plate current measurements.
