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What to look for in a tube tester

Wigwam Jones

Wigwam Jones

Caesar non supra grammati
I looked but did not see this topic covered in the recent past on AK. Hopefully I'm not bringing up an old subject.

But I have been somewhat curious lately; I'm probably far enough into tube toys now that I'll need to get a tube tester at some point. I see them from time to time on various places, but I see prices all over the place. I sense that some of them are considered better than others because some draw lots of bids and some go unsold.

I saw a reference in another thread just now about tube testers in wooden boxes being unable to test all tube types. This makes sense.

Any other tips, tricks, things to know? What does one look for in a tube tester? I hear brand names like Hickok being tossed around. What are the good brands, what are the good models and types? What needs to be tested on a tube to ensure it works properly?

Thanks!
 
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for just go/no (emissions) testing the Eico 666 is a well regarded unit . and it has a steel cabnet. $200. I have one.
Then the hickoks are much sought after which test mutualconductance or gm. they are spensive unless you can get one that works not damaged $200, as the 533. they go up from there. I have this one too. I gave $200 apice for each of my testers in excellent condition.
your needs will dictate what you should get.
 
ferninando said:
for just go/no (emissions) testing the Eico 666 is a well regarded unit . and it has a steel cabnet. $200. I have one.
Then the hickoks are much sought after which test mutualconductance or gm. they are spensive unless you can get one that works not damaged $200, as the 533. they go up from there. I have this one too. I gave $200 apice for each of my testers in excellent condition.
your needs will dictate what you should get.
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Thanks! Can you give me a little rundown on what mutual conductance and gm is? I hear the terms, but I confess I do not know what they mean. For that matter, what is emission testing and how is that done?
 
Emission is a test of the cathode - every tube is basically tested as a diode. How much current can it pass vs. voltage applied. This can detect a worn-out tube but can't be used for matching. Emission testers can also detect element-to-element shorts and SOME can detect grid leakage (Sencore Mighty Mite, for instance). Emission testers are easier to use and often have a larger list of tube data (and it's not too hard to figure out the settings for a tube that isn't listed). I like the Knight 600 for this reason, but many other ones are similar.

Transconductance (mutual conductance, gm) is amplification factor - the ratio that plate current changes vs. the change in grid voltage. Transconductance testers have more settings for each test, but tell you more about the tube's performance. Output tubes can be matched (though in-circuit matching is better). Some testers (B&K and SECO) have prewired socket panels that simplify testing - pick the right socket and set two controls, press the test buttons. Great if the socket is available for the tube you want to test... on the B&K 707, 6BQ5, 6V6, 12AU7, 6CG7, 6L6 are quick, 7591, 7868, many others are not (and tested for emission only). 12AX7s measure "good" at 17 on a 0-120 scale - not much resolution - though there's a mod I can make to improve that.
 
Tom Bavis said:
Emission is a test of the cathode - every tube is basically tested as a diode. How much current can it pass vs. voltage applied. This can detect a worn-out tube but can't be used for matching. Emission testers can also detect element-to-element shorts and SOME can detect grid leakage (Sencore Mighty Mite, for instance). Emission testers are easier to use and often have a larger list of tube data (and it's not too hard to figure out the settings for a tube that isn't listed). I like the Knight 600 for this reason, but many other ones are similar.

Transconductance (mutual conductance, gm) is amplification factor - the ratio that plate current changes vs. the change in grid voltage. Transconductance testers have more settings for each test, but tell you more about the tube's performance. Output tubes can be matched (though in-circuit matching is better). Some testers (B&K and SECO) have prewired socket panels that simplify testing - pick the right socket and set two controls, press the test buttons. Great if the socket is available for the tube you want to test... on the B&K 707, 6BQ5, 6V6, 12AU7, 6CG7, 6L6 are quick, 7591, 7868, many others are not (and tested for emission only). 12AX7s measure "good" at 17 on a 0-120 scale - not much resolution - though there's a mod I can make to improve that.
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Thanks!

So let's say a person was just getting started - maybe had a couple tube amps, both new and old, and a small collection of miscellaneous tubes, mostly fairly modern (9 pin versus octals). What do you think would be a good tester to start out with?
 
Hello!

Jackson tube testers are well made and can sometimes be had on the cheap. I sold mine to a friend who had an Eico 666 and he finds the Jackson easier to use. There are several different versions. Jim Cross of Vacuum Tubes Inc wrote a great book on these testers and sells them on his site. My copy went with my tester. I would buy another Jackson in a heartbeat. I have 2 Hickok's and have owned Sencore, B&K, Heathkit, Eico and Precision. The biggest revelation for me is that these are not precision test instruments in many cases. That could be a whole 'nother discussion. Robert
 
Some good info in this thread: http://www.audiokarma.org/forums/showthread.php?t=428922

I'm in the same boat as you. After a lot of reading, I realized that tubes can only be properly matched 'in circuit' and that a mutual conductance tester really won't do this for you (someone correct me if I'm wrong on this). I decided that mutual conductance was overkill and over priced for a hobbiest like me. I'm not in the business of selling tubes and really only want to be able to ensure the tubes that I am buying really are good. I eventually picked up a working Sencore Mighty Mite emissions tester and couldn't be happier.

Also discovered that it really pays to check the tubes you are buying! I've had to return two sets that weren't as advertised (No AKers involved).
 
njcanuck said:
Some good info in this thread: http://www.audiokarma.org/forums/showthread.php?t=428922
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Thanks! Yes, I had seen that thread, but could not make heads or tails of it. The answers given pretty much require you know what the words mean before you can decipher what the words mean, you know? "I think the gm in that is not great." Oh, I see, what's gm? (it was answered in this thread, thankfully). "I don't like the roll." The what? What's 'the roll'? I still don't know what that means.

I appreciate very much the advice that the experts share - can't thank them enough for taking the time to do it! Sometimes I think they're not aware they are using jargon that only someone who knows the answers already can understand...which leaves newbies to tubes like me scratching our heads!

It's all good though. Thanks for the info; glad I'm not the only one!
 
The "Roll" is the paper roll under the window that contains all the settings. Not all testers have a roll - mine came with the settings in a handbook.
 
If you are just starting out with trying to aqcuire a tube tester you will want to start out with an emissions tester to weed out the good from the bad, some people just stop with an emissions tester because really that is all you need. Like was said above once you have sussed out that a tube does not have shorts and passes an emissions/grid leakage test only an in audio circuit test will tell you if the tube is up to snuff.

If after getting a decent emissions tester you want to wade in the waters of mutual transconductance testers do a little reading on the subject to find the shortcomings of these testers to determine if you even want to purchase one.

Good emissions testers at reasonable prices are the Sencore Mighty Mites, Jackson, Precision, Eico, B&K, et al.

Try this link to acces the tone lizard through the intarweb archive machine, there is great info at the tone lizard site.

http://wayback.archive.org/web/*/http://tone-lizard.com
 
Thanks! It appears that the tone lizard website is no more, but the wayback archive had the page. I appreciate you posting the info.
 
ferninando said:
tone lizard is running fine for me. the link given is good and works.
http://tone-lizard.com/Jackson648.html
http://tone-lizard.com/Tube_Testers.html#advertising
enjoy your tour in tube tester land.
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OK, thanks, that's interesting. I do not have problems reaching any other site on the net that I'm aware of, but I cannot get to that domain. It cogitates over it for awhile and then gives me an error message. I can't ping the domain either. Perhaps my ISP has that blocked, or their ISP has my domain blocked.
 
We kinda need a sticky thread with links to tube tester discussions.

Whatever you consider buying, ask whether it's been restored and/or calibrated.

For example the old Hickoks have a couple of caps in them, and most testers are going to have a slew of resistors. The caps for sure should be replaced just like in an amp. Hickocks have a couple of tubes inside too, so you want to make sure those are OK. Finally there's the calibration, which you can do yourself if you have the instructions and the requisite calibrated certified test tube, or you can ship it off and pay $$ to have it done. Admittedly none of my testers are calibrated, but they're OK for a go/no go or comparison testing between choices of tubes. I plan to send off my best one for calibration soon as I get around tuit, and sell several others at AK to thin the herd. I have way more testers than I can use at once, way more than I need considering how much tube work I actually get to do.
 
Wigwam Jones said:
OK, thanks, that's interesting. I do not have problems reaching any other site on the net that I'm aware of, but I cannot get to that domain. It cogitates over it for awhile and then gives me an error message. I can't ping the domain either. Perhaps my ISP has that blocked, or their ISP has my domain blocked.
Click to expand...

I've had problems with that site, too. Some days I get in, some days I don't. Seems pretty random.
 
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