Looking on the net shows them (CV378/GZ37) as the same. If you don't have the settings on your other testers, using the 5AR4/GZ34 will give close, but not exact readings I believe.
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Thanks for that information Hifihvn. I tried it with my other testers and it worked well.
Now how about the PX25 tube? None of my testers has that one listed. Do you know of another setting that might work for it?
I did a quick check on the net and came up with CV1040, CV1064 and CV1343. I'm a bit hesitant to try any of those with a very expensive tube unless someone knows it is safe.
I think these are ok to try. It's hard as the sources from Europe and UK are a little different values, plus different specs from different brands in some cases. I hope these will work. PX25, CV1040, VR40, PP5/400, if your tester has a setting for one of these four numbers. The other VR numbers you mentioned even has less info that I can find. These seem to be similar in specs, and all have the same pin connections, and 4 volt filaments from what I can find. I'm not familiar with these tubes being used in the US. If you plug a tube in the tester and it gives a hum that sounds too loud, pull the tube quick because something may not be right, and the same if the fuse-lamp comes on in a Hickok made tester. Also, if the meter bangs to the full end (it could get damaged), would be a sign that the settings are wrong, or something is wrong with the tube. When you test for value read out on the meter, don't hold that button down long, as they say it can be hard on a tube. Once the tube is warm, and after you check for shorts/leaks, it should only take a few seconds to get the Mutual Conductance (value) reading from the meter. I hope this info is ok, and works.