# Tube Testers



## plato67 (Jan 13, 2008)

Anybody got one? I'd like to be able to test old tubes. Which model is a good beginner unit?


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## Geek (Jun 5, 2007)

Hi,

Look for a mutual-conductance (also known as transconductance) tester. They are more, but are also the only ones that are really useful.

Cheapies tend to be straight emission testers, which are an OK indication of tube life, but tell you nothing else about it - the grids could be burned right out of it and it'll still test good 

Another type (which I have) is the grid-shift trester. Less expensive and less complex, but will only give you DC analasys (though if you're patient, you can actually use them to figure the plate curves of the tube under test)

I had a B+K 747 transconductance tester and it was great 

Cheers!


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## greco (Jul 15, 2007)

_The B&K 747 is a mutual conductance tester which will accurately reflect a tube's ability to amplify a signal. The other testers are called emission testers and they measure the flow of electrons from the cathode. There is not a perfect relationship between mutual conductance and cathode emission. One would never expect these three different models of testers to show agreement on much of anything--but a bad tube on both the Knight and SICO should show bad on the B&K. The reverse would not be true. The B&K should find some bad tubes that do not show up on the other testers. On the shorts tests you are at least measuring the same thing--leakage between the tube elements. But here again the sensitivity of the tests varies widely. The typical neon light shorts indicator lights at 250K of leakage. The shorts tester on the B&K will detect a 1 meg short, and as little as 100 megs of leakage to the grid of the tube. The B&K is the superior tester of the three, and assuming it is in good working order and calibrated properly I would go with its results. The B&K won't test old big pin radio tubes, and this is a limitation. For the more modern tubes the B&K is a very nice unit, although I don't care much for the plastic case and breakage prone plastic hinges._

I found this and thought it might be of interest. I know nothing about tube testers, just enjoying the thread and learning.

Dave


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## tubetwang (Dec 18, 2007)

most Mu Conductance testers test for shorts, grid leaks, emission and transconductance.

Make sure you have the operation manual and most important have it calibrated...

I had mine (Sencore MU140) calibrated by Chris Hayedt in the U.S.

Sadly he passed away years ago...


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## toby2 (Dec 2, 2006)

*tube tester*

The problem with most tube testers is that they will just give you a ballpark 
indication as to the health of a vacuum tube . The voltages in most testers 
is much lower than at typical operating voltage that you would find in a preamp or poweramp . A 6L6 may test fine in your fancy Stark tester but once it is dropped into an amp , that is where the real test happens .


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## Geek (Jun 5, 2007)

Too true!

I had some Sylvania 6V6's that tested great, but became a light show in the amp 

So now I test 6V6's in my actual amp.

Cheers!


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