Tube Testers

[jnewlyn]

I'm thinking about buying a tube tester. Hickok seems to be a pretty big name. In very basic and general terms, what are we looking for in a tube tester. It need not be fancy stuff. Just basically want to plug in a tube and see if they are good or not and maybe how well matched they may be.

[Cheech]

I have a Hickok 533a. Tube testing is a interesting hobby. None of these testers actually test tubes at their rated operating voltages. I am not able to match power tubes on my Hickok because of this. The Maxi-Matcher is a far better tester and matcher for guitar type tubes. That tester is expensive however.

Tube testers are good for checking if tubes are safe to install in your amplifier(no shorts). Tester is also good for telling me the relative life left in the tube. I assume the number it gives me is the reading ability of the tube to amplify. I have some tubes that are not gassy and no shorts but just test way low. 1250 nominal good and they test 600 range. These tubes I deem bad. I have some tubes that test way over the nominal values. Tubes are labeled 12ax7 but test into the 1700,1800 even up to 2000. Sylvania long plates test high for me. Each tube tests differently and just by my experience I would not rely on the nominal value for new tube. More reliable would be how good the particular tube was when it was new. I record the date and reading of tube tubes I test on their respective boxes. I can compare this with a future test and see the condition later. However, even then I can get a different reading than before on the same tube that I did not touch but still its close. The tester can pick out weak tubes. Terry told me that the tester can also say my tubes are good and matched but in the real circuit they might not be. My tester will not guarantee the matching of tube tube because of the lower plate voltage.

This testers noise test checks for shorts in the tube through a old radio set. You provide the radio.

This tester will not test for micro phonics.

[jnewlyn]

Oooy vay. I need to learn up on tube testers I guess.

[Cheech]

I recommend you read the Idiots guide to tube testers. Hopefully the site will be back up soon. This is very informative and you will understand better after you read it.
http://tone-lizard.com/Tube_Testers.html

There is a schematic for a tester circuit you can build for both types of jobs.

http://greygum.net/sbench/sbench101/#TubeTest

RAT tester project is a tube tester that measures GM conductance that you can build. There is a bill of materials however this comes with no gauges or scales or any fancy stuff. You have to source all your own parts and find your own meters or use your multi meter.

RAT Noise tester is a tester that can detect noisy tubes. There is a schematic on the website as well. This could be built as part of the RAT tester but you can get a stand alone power supply for it.

There is another tester I seen to match power tubes. This tester uses a fender style power transformer and a spare chassis you might have to test the tubes at rated voltage for idle current. Like putting them in a amp but without the speaker or output transformer. http://home.comcast.net/~priceamp/

My hickok works pretty well for what I need it to do but if you do get a hickok remember these things are old and do need calibration every once and a while. Mine is close from my own measurements however I never did buy a reference tube yet to verify the scales. You have to be careful in what you buy if you look on ebay. My tester came with missing screws in the panel and no tubes inside. Terry got me some tubes for it. I checked some of the circuit values. Everything seems well and the controls calibrate per the procedure.