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

[Tubetwang]

Save yourself some work and get one from one of the U.S. tube testers hardcore gurus.

Otherwise take a chance on a reputable Transconductance one and get it calibrated.

Make sure you get one that test the tubes you use and also make sure that the tube reference companion book is included.

I got a Sencore M140 that test emission, grid leakage, shorts, trans-conductance from an old local tv repair dude 8 years ago and send it to Chris Haedt for calibration.
He did a marvelous job and gave me a complete report and ajusted the tester for my house current. Great to deal with. He wrote lots of articles on tube testers.

He later passed and will be missed...

[billyz]

Most tube testers have limitation, especially regarding the voltage at which they test at. But, they can be helpful to determine tube life left and test for obvious shorts. My favorite is the Military TV7/DU, Hickock is another good brand, there are others. But , there are more than a few that are pretty useless, they will tell you if a tube filament lights up and thats about all.

There are some custom built ones that do test at high voltage and measure plate current etc., but mere mortals must be content with something less.

here is a good article on them.
http://tone-lizard.com/Tube_Testers.html

[muchxs]

Most tube testers have limitation, especially regarding the voltage at which they test at.

Consider that 12AX7s are perfectly happy down around 150 volts. Miniature power pentodes (6BQ5s) and beam power tubes (6AQ5, 6V6 et al) perform at low voltages. High voltage is great if you're testing 6550s or 8417s. Accuracy is accuracy, a good tester is still a good tester even if you're not testing at 400-450 volts. If you test a lot of 6L6s and EL34s why not build a jig (essentially an amp) and match current draw in-circuit?

But, they can be helpful to determine tube life left and test for obvious shorts. My favorite is the Military TV7/DU, Hickock is another good brand,

Hickok was the primary U.S. military contractor for the TV-7. If you ever see anything built by Stewart-Warner under military contract be sure to look inside, "bulletproof" doesn't begin to describe it.

On your tube tester gurus... I sold some 6SN7s to one of the TV-7 "gurus". He took forever to pay and gave me a hard time. Do it yourself, you can pay someone to screw it up for you or you can screw it up yourself for free! The calibration procedure isn't difficult especially if you have multiple testers to match to a known reference.

[billyz]

It is true most good testers run around 150 volts which is pretty good for a 12a variant etc. Hickock did make most of the TV7 too. I have had Jacksons, Westron, Heath, sencore and a few others. I do like the TV7's even though some of the others let you test both halfs of the dual triodes with out switching anything. They just seemed to have other issues that made me not trust them.

I always test tubes in the amp anyway for plate current and noise.

[Ears]

Did anyone ever manufacture tube curve tracers?

[BluzMike]

I happily own two old Hickocks for pre-amp tubes. If I remember correctly, they do not go over a plate voltage of 230V or so, they do not help much for power tubes. If testing higher numbers of tubes regularly, the need to switch between both systems in double triodes kills quite some time, so that I decided to operate two Hickocks next to each other, one set for system 1, the other for system 2.

Amongst the 'affordable' testers with an acceptable plate voltage I may recommend the Maxi Matcher, which lets you go up to 400V. This is still a bit less than most amps have on their plates, but gives good enough results for me. You have to re-check in the actual amp anyway. And, after all, I usually prefer slightly mismatched tubes anyway.

With my unregulated Maxi Matcher I need to go through the tubes twice at least, as the value of one tube is depending on the others'. First run is to create an initial rough order according to plate current, second is to get sets of 4 tubes with close enough plate current values, which are also checked for transconductance.

I believe that a +/- 5% match on PC is really good enough, and for transconductance you can live with up to +/- 10.

Slightly unbalanced power amps sound more lively to my ears and offer better harmonic content. But your taste might differ from mine, which is based on my experience with old Marshalls and Fenders primarily.

[Andy Le Blanc]

I've been eye'n the maxi-matcher
what did you mean specifically by "unregulated Maxi Matcher" ?

[v846]

I use a B&K 700, has a good shorts and emissions test which is most important testing used tubes thought the transconductance test on the 700 for 12AX7 leaves much to be desired but it's so easy to calibrate even I can do it
For matching I have a testbed amp with 1 ohm cathode resistors on the octals that runs about 400 on the plates then ultimately the real test is in the amp... works for me

[BluzMike]

I've been eye'n the maxi-matcher
what did you mean specifically by "unregulated Maxi Matcher" ?

The standard version has an uregulated power supply. For US versions, you can order a 275 USD upgrade, but for the export version it would have been 475 USD, which I felt to be way too much. But ordering the EL84 adaptors turned out as a very good investment.

Tom Peters wrote me that the inteferences would not occur with this upgrade, but you better reassure this with him.

I use the MM mostly to check the power tubes of amps coming in for restoration or repairs, but also to find usable matches of used vintage American and European tubes. After owning one for a while I definitely would not wnat to miss it.

My experience with Tom has been perfect. Great communication and quick service, so highly recommendable.

[Andy Le Blanc]

thanks...... practical experience is best
a regulated supply on a piece of test gear seem like it should be standard
glad to hear a great refference none the less....

[The Tube Doctor]

I've been using an AVO CT 160, which is a really serious piece of British military kit. It still has the stencilled name of the Sgt. to whom it was issued. Anode voltage to 400 max, screen to 300V. Tests heaters, insulation resistance, gas and is adjustable to all different world-wide mains voltages. Measures grid current, anode current, negative grid voltage, mutual conductance and much more.
Worth-while gear if you can find someone willing to part with theirs.
And no, I'm not willing.

[selloutrr]

truthfully without going tnrew the steps of building your own test bench and calibrating lab grade test equipment there are 3 quality new tube testers for preamp only the vacume tube valley small characterizer ($1000) for output tubes the maxi matcher ($800) and the amplitrex at1000 curve tracer ($2600) I've spent years researching reading trying and passing on tube testers most of the older hickok , b&K ,RCA, sencore and TV all are under rated voltage for true operating test and none of them share a common standard measurement. it sucks but unless you collect tube testers buy one that fits your need not your wallet you'll only have to do it once, or make a friend if you only have a few tubes to test personally I test over 300 tubes a month so I choose the best I also have a hickok 539c and teletronix 570 but most of my tests are on the amplitrex at1000 and maximatcher 500+ volts and safe to operate regardlesd of what tester you Buy use a constant voltage transformer so you can get a solid reading sola makes a nice transformer you can find on ebay cheap. best luck