On the look out for a tube tester!!

[DrGonz78]

So I am finally at the stage where I want to invest on a tube tester. Before I go forward I want to ask some advice here on MEF. I am looking at a B&K tube tester model 700 that is fair condition. I see one that I would need to recap & clean it up to good working condition. Then there are other ones that have 12ax7 mod and have been all fixed up nice. Main point is the price as I really don't mind learning how to make it work like new and save a few bucks.

So what do you use? Which ones should I possibly avoid? I will also be asking questions no doubt later when I get a tester for recommendations on using the thing. I guess in a nutshell I have yet to use one so I have a learning curve to get over.

[pontiacpete]

I have the B&K 700. It worked when I got it about 6 years ago. Broke down after a couple of years and replaced a cap or 2 and it's still working. Nice simple unit.

[Jazz P Bass]

Personally, I do not use a 'Tube Tester'.

You want to test the tube, plug it into a working amp & do a few measurements.

[tedmich]

Old tube testers are fun, although far from an essential tool IMHO. The B&K 700 seems to be decent unit with a version of Hickok transconductance. I have hundreds of tubes and the only one that every tested BAD was my treasured NOS Amperex 12AX7 that had been V1 in my main amp for 3 years. And I already knew it was bad, as it stopped working in the amp.

[TomCarlos]

I have a Sencore Mighty Mite VII, TC 162...

I'm tested tubes and this unit showed the Emission as "Good." But in reality, some of these tubes could not produce the full gain that others could. I discovered that when I put the tubes back in an amplifier and checked the voltages (the output as specified on the schematic) and compare that with new tubes. So the Tester really was nothing more of a "It's good to the point where the tube is doing something but not necessarily working at top performance."

JPB has it right... the real test is checking the tube "in the amp."

I have an older Crate Blue Voodoo tube amp that no one wants. I am going to gut that thing and use it for tube testing. I am going to disconnect the output section and have that on cables if I need to test output tubes. For the input section, I am also going to remove anything that is not needed (after the input stage). I'll simply build a jig where I can put in different preamp tubes and test both sides. Yes, there will be specific measurements I need to see- that is how I will rate a tube for it's quality. The jig will have switches for different resistors, caps, etc... and this should accommodate 12ax7, 12au7, 12at7, tubes. I think this would be a cool project exercise and I might learn something!! If nothing else, I will be testing tubes in a real world condition outside the amp under repair.

Anyone else build something like this?

Tom

[nevetslab]

I've an old Hickock 539A Tube Tester that I bought in 1977, rarely used it back then. It sat around for a few decades, but did move it out to my shop at the sound stage/equipment rental depot, with the passing thought of restoring it (one of these days). But, I too agree........the real test is checking the tube "in the amp", and that's just how it get's done.

I had earmarked a Fender 'The Twin' as a test bed for tube testing work, one that came from the 'boneyard'. But, as usual, available time to turn it into something that would be a good sorting fixture for all the tube pulls.....6L6GC's, 5881/6L6GB's, EL34's, 6550/KT88's that I use the most of, I normally find myself doing all that in the amp being serviced. Same with the preamp tubes. I do need to get the upper hand on the growing piles of power tube 'pulls', as there's so many tube amps in our rental inventory, and never enough funds to keep a well-stocked inventory of fresh matched sets to pull from. And, just hate to have to break up a set when you only need one tube. Put a new quad set in, now ya have 3 pulls reasonably close to add to the pulls stash. Gets time consuming, as you all know.

I do have Operators/Service Manual for Tektronix' 570A Tube Curve Tracer, and once had the idea of building one. But, not in this lifetime.

[John_H]

I've got a Triplett 3413 from the mid 50's. I'ts ok as emission testers go. Testing tubes in an amp is fine 'til you come across a shorted power tube.

[Sowhat]

Testing tubes in an amp is fine 'til you come across a shorted power tube.
[ATTACH=CONFIG]30893[/ATTACH]

That's true, but you do find out in a jiffy with one of those!

I use the test it in an amp method as well, I've never found a tube tester that really tells the true tale anyway. Hearing is believing.

[g1]

I have a Stark (Hickock) 600. Like most others here, don't use it much for guitar amps. But I do get it out for the old radio stuff. My radio chops aren't good enough that I can get by testing in circuit. And I don't often have those kind of tubes to be able to swap another in, so I like to confirm bad before ordering a replacement.
Also, should you find some awesome valuable tubes in some chance flea market buy, if you want to sell them on ebay someone will inevitably demand they show good on a tube tester .
Socket extensions are a big plus, if you wear out a common socket, you just replace the extension instead of having to wire in a new socket.

[52 Bill]

I've got a couple of B&Ks that I keep at home for testing oddball radio tubes. At least they keep me from buying tubes that I will never use again just to see if that's the problem. They work pretty well and have held up for a couple of generations now.

At work I have my TV-7 that sits collecting dust, although a couple of weeks ago a guy came in and asked if I could test the tubes from his radio for him. He had a dead rectifier tube.

[Pedro Vecino]

I use a Hickok 800 to measure relative transconductance in preamp tubes and works really well. It is a very useful information when selecting units within the same model/manufacturer to equip each amplifier and to determine the status of used tubes. I also use it for detect short circuits and to estimate the lifetime of power tubes. However no use to matching. That I do in amplifiers, with real high voltage.

[The Dude]

I have a Sencore Mighty Mite VII, TC 162...

I have one of those, also. In general, I wouldn't say tube testers are useless. You just have to know their limitations.

[danman]

I also own a Hickok 800 which I use for testing old pulls and Ebay buys occasionally. One thing to remember is that you will need to refurbish and recalibrate most old testers that you find for sale these days. Most will have old caps and drifting components that will need to be changed to get a fairly accurate tester. Most of this info is available online and isn't to hard to do if your handy with a schematic and soldering iron. Another thing to watch for is that alot of the older transconductance testers use a 5 volt signal on the grid for testing. If you are buying it primarily for audio tube use, this can be a little high for certain tubes such as the 12ax7. Most of the later Hickoks and some of the higher end brands use a much lower (0.5-2.5v) grid voltage which provides a better test result for most of the audio tubes that we use.

[Enzo]

I have a Sencore something or other under my bench. I use it almost exclusively as a footrest. I also have a little one, maybe 8x10". I have fired it up and verified it worked on a couple tubes, and now it sits as eye candy in the other room here.

I don;t use a tester in my work. When a customer asks if I have a tube tester, I say "You're talking to him." Har har...


The only reason I don;t sell the Sencore is as soon as I do, I will find an odd 6XYZ42 tube (yes, I made that up) and will want to know if it functions.


But if you want one, no reason not to.

Ones to avoid? Ones that work like crap. A top of the line Hickok is worthless if all the controls are intermittent. And some cheap piece of crap that works reliably is as good as anything, to me. it is like a guitar amp. Age is no issue, condition is. If you are looking to buy local, then take a few tubes along, set up for each one, and run through the test sequence for each. If the guy isn;t willing to let you see it work, then wish him a nice day and leave.

Older machines might be fine, but if they are so old they don;t cover modern tubes, then stop and think. It better cover EL34 (6CA7), 6550 would be nice. 7027 for the old Ampegs? And any of the fun power tubes with 6789 in the number. 7189, 7591, etc. And really, it better handle miniature tubes like the 12AX7 and related.

[The Dude]

I have a Sencore something or other under my bench. I use it almost exclusively as a footrest.

That's funny. I don't use mine as a footrest, but it does get used quite often as a weight when I'm reconing speakers. Reconed speaker facing up, Black Widow basket facing down on top, and tube tester as weight on top of that. Hey,......it was just sitting there doing nothing anyway.