How well do tube testers work?

[George Magvas]

Just wondering what you all think of the tube testers that are available on Ebay Etc. The ones I've seen are usually from the seventies and were used to test Tv and radio tubes. I've heard that they don't supply a high enough B+ voltage for a proper test. If these are not effective is there a tester that is?
Thanks

[PRNDL]

They're what they are.

Lower cost testers use low voltages to test the tubes, and perform basic tests. Those that put high DC voltages are typically a LOT more expensive. Some techs test tubes in an actual amp and write the bias current on the box as a way to match tubes.

For great articles, see this web site
http://tone-lizard.com/

[stokes]

For the most part,they will only tell you good/bad,even the best Gm testers can give erroneous results.Emission testers are the bottom of the barrell,so to speak.Check out www.alltubetesters.com he has some good info there.I have a Weston 981-3 which is a pretty good Gm tester.I recently tested a pair of old 6V6's which I know are bad,they sound weak,one of them has absolutely no getter left and yet they test very good and seem to match for transconductance.Yet when I put them in my tube matcher they draw almost 20ma's different.This tester is usually pretty reliable,but every now and then you get a tube that defies logic.The only true test is in the actual circuit or amp they will be used in.

[Enzo]

My thoughts:

Tube testers will verify that a tube is bad. If it says a tube is bad it most likely is bad. What they tend not to be good at is telling you a tube is good. Stokes report is a perfect example of that. Even if the tester tells you a tube works, it won't tell you if the tube has lost its tone. The vast majority of testers won't tell you if the tube is noisy or if it is microphonic, and won't tell you the tube is hummy - like all those SOvtek 7199s that hum terribly.

AS PRNDL says, if you want to know if a tube works, stick it in an amp.

[kg]

whenever i was testing batches of tubes, i'd rig up a test jig.

octal relay sockets are very handy for that. screw one into your bench temporarily and use clip leads to hook up heater, bias, and b+. a nice non regulated linear supply on a variac makes for a handy b+ rail. check your currents at a couple of different operating points, write 'em on the tubes, and match 'em up.

the only tube tester i ever thought was worth anything was the one steve bench designed/built. the plans are still on his website.

[George Magvas]

Tube testers

Thank you all for some great info and links
George