# Tube testing at home?



## aC2rs (Jul 9, 2007)

How do you test your tubes?

Are there any inexpensive tube testers that are readily available?

Or do you wait until there has been an obvious failure before replacing them?


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## keithb7 (Dec 28, 2006)

I have tube testers however basically they test for shorts. When a tube shorts, you'll know it. Problem is, you may think something else is wrong with the amp. Tube testers also test thermionic emmission. I know....That sounds cool to me too. I am not educated enough to fully explain it. I think thermionic emission is when you heat up the center heater elements in a tube. Electrons fly from the cathode thru the grid to the electrode. The tube testers measure, (I think) how many electrons fly off from the cathode. Eventually tubes wear down. Get weak. Not many electrons move off the cathode. Again, I suspect. Someone who knows the real story can clear this up. 

You can check all these things. Simply eleminate the features of a tube tester, by swapping in known good tubes. I recommend a couple of spares on hand. Swap in good tubes and test with your ears. If the symptoms improve, problem solved. Another thing I do is plug in the amp and turn the volume down so its not too loud. Tap the tubes with the eraser end of a pencil. Hear fizzy crackling? Popping? Either a tube socket needs attention or a microphonic tube? Clean tube socket pins. Re-index sockets if needed. Try again. Eliminate possibilities. No better? Try a new tube. Tube testers are convenient but not the panacea.


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## GTmaker (Apr 24, 2006)

Im sure there are plenty of remedies on how to tell if a tube is bad....
If you really want to know, then you get a tube tester...or find someone who has one.

I got me one of those fancy dancy tube testers a while ago...
seem to do the job it is designed to do..
G.

here is a pic of mine (click on the pic for a full view)


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## greco (Jul 15, 2007)

GTmaker said:


> I got me one of those fancy dancy tube testers


I have 3 tubes that I want to give to you to test. Please remind me.


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## GTmaker (Apr 24, 2006)

greco said:


> I have 3 tubes that I want to give to you to test. Please remind me.


this sure smells like a free "all day breakfast"....
G.

I test all tubes for free....if you want to know the results that's a different story.


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## greco (Jul 15, 2007)

GTmaker said:


> this sure smells like a free "all day breakfast"....
> G.
> 
> I test all tubes for free....if you want to know the results that's a different story.


You can keep the tubes after you test them...and buy me breakfast as a gesture of your appreciation of my kindness and wonderful gift.


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## BMW-KTM (Apr 7, 2015)

Buy yourself a Knight Tube Tester
You can find them on eBay for well under $100


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## High/Deaf (Aug 19, 2009)

There is a cool hobbyist radio club that operates in Coquitlam. They have tons of old tube radios and electronics, I'm sure they have a few tube testers. They are also into talking about old-style gear (i.e. most new tube guitar amps these days). I plan on taking some of my older tubes up there and testing them.

But I think we stress too much over tube life and wear. They didn't do that so much when all they had was tube equipment. The ran tubes till they didn't work anymore and then swapped them for ones that did. Mind you, they weren't using (or is that abusing) tubes like we do nowadays.


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## aC2rs (Jul 9, 2007)

I have a lot of tubes sitting around which I believe to be good.
That said, I sent an amp out for repair to Yorkville Sound a few years ago with new tubes in it for an unrelated issue. The issue was repaired, but they also replaced one of the 6L6s as it was bad.

Since then the thought of finding an inexpensive tube tester for home use has something I have been considering on and off.
The problem with the listings on the auction site is, aside from the fact I don't know what I'm looking at, that they are neither inexpensive and /or they are so old and beat up that who knows if they even work.

I've only ever had one obvious failure, when a 5881 exploded - I just followed the smoke trail to find that one


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## GTmaker (Apr 24, 2006)

greco said:


> You can keep the tubes after you test them...and buy me breakfast as a gesture of your appreciation of my kindness and wonderful gift.


I've just enrolled in a " improve your negotiating skills" class.
The idea is that the cost of the class will be cheaper then constantly buying lunches.
G.


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## ezcomes (Jul 28, 2008)

so...i have a pair of power tubes that i want to test...will tube testers be able to tell you if they would match each other...or...would i need a pipe dream for that?


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## jb welder (Sep 14, 2010)

Tube testers will tell you a tube is bad when it is obviously so. It won't tell reliably that a tube is good, only that it is good in that particular tester. Usually they test at much lower voltages than tube amps operate at. So (especially for power tubes) they may give you a false positive reading when a tube has an intermittent fault or can't handle higher voltages.
They may come in handy for certain things, but most guys/shops that are doing a lot of repairs don't use them very often. Like Keith said, substitution with a known good tube is the common troubleshooting method.


ezcomes said:


> so...i have a pair of power tubes that i want to test...will tube testers be able to tell you if they would match each other...or...would i need a pipe dream for that?


There are some higher end units that are suitable for matching tubes, but they are expensive, like the maximatcher:
Maxi Test : Digital Tube Tester, Vacuum Tube Testing, Power Tube, Dual Triode, Maxi-Matcher, Maximatcher


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## keithb7 (Dec 28, 2006)

Heres my interpretation, someone formally educated can set me straight.

A standard thermionic emission tube tester cannot test tubes to pair, or match them. A more complex tube tester somehow measures milliamp draw with the tube acting as if it were in service. These type of testers are more expensive. If you have a bunch of spare tubes lying around, and a thermionic emission tester, you can test for shorts and tube strength. If you are comfortable working around 500V inside a live amp, and know how to not get killed, you can insert unmatched power tubes and test each for milli-amp draw with a DMM. This is the same method I use to set power tube bias. By testing each power tube's milli-amp draw, you can deduce how well matched the two tubes are. One will be drawing more milliamps than the other. Trial and error I would think, you could get pretty close with a matched pair. That's my experience anyway. Not simple but can be done. Do not go in an amp and attempt this without proper training. Deadly voltages in there that you'll be dealing with.


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## ezcomes (Jul 28, 2008)

So i guess, in my case...i can try to put these tubes into an amp...see if the work and trust that they are close enough to not cause issue


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## High/Deaf (Aug 19, 2009)

keithb7 said:


> Heres my interpretation, someone formally educated can set me straight.
> 
> A standard thermionic emission tube tester cannot test tubes to pair, or match them. A more complex tube tester somehow measures milliamp draw with the tube acting as if it were in service. These type of testers are more expensive. If you have a bunch of spare tubes lying around, and a thermionic emission tester, you can test for shorts and tube strength. If you are comfortable working around 500V inside a live amp, and know how to not get killed, you can insert unmatched power tubes and test each for milli-amp draw with a DMM. This is the same method I use to set power tube bias. By testing each power tube's milli-amp draw, you can deduce how well matched the two tubes are. One will be drawing more milliamps than the other. Trial and error I would think, you could get pretty close with a matched pair. That's my experience anyway. Not simple but can be done. Do not go in an amp and attempt this without proper training. Deadly voltages in there that you'll be dealing with.


How do you measure the tube current? Do you have a device that lets you connect an ammeter in series with one of the tube pins? Or do you measure the voltage drop across a known resistor in series?

I've thought about buying one of those jigs that inserts between the tube and the amp socket and allows you to measure current directly, but most of my amps are either cathode biased or have test points on the back. For the two amps that don't have that (DRRI and 5E3), it would be useful if it works well.


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## davetcan (Feb 27, 2006)

keithb7 said:


> You can check all these things. Simply eleminate the features of a tube tester, by swapping in known good tubes. I recommend a couple of spares on hand. Swap in good tubes and test with your ears. If the symptoms improve, problem solved. Another thing I do is plug in the amp and turn the volume down so its not too loud. Tap the tubes with the eraser end of a pencil. Hear fizzy crackling? Popping? Either a tube socket needs attention or a microphonic tube? Clean tube socket pins. *Re-index sockets if needed*. Try again. Eliminate possibilities. No better? Try a new tube. Tube testers are convenient but not the panacea.


*"Re-index sockets if needed" - *what does this mean?


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## cboutilier (Jan 12, 2016)

davetcan said:


> *"Re-index sockets if needed" - *what does this mean?


Tighten up the contacts for the pins.


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## davetcan (Feb 27, 2006)

cboutilier said:


> Tighten up the contacts for the pins.


Oh, OK. Indexing a socket to me would mean rotating it, which one should definitely not do.


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## greco (Jul 15, 2007)

davetcan said:


> *"Re-index sockets if needed" - *what does this mean?


IIRC, I have read that referred to as "re-tensioning"


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## Alex (Feb 11, 2006)

aC2rs said:


> How do you test your tubes?
> 
> Are there any inexpensive tube testers that are readily available?
> 
> Or do you wait until there has been an obvious failure before replacing them?


Orange came out with a tester a few years ago.


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## davetcan (Feb 27, 2006)

Alex said:


> Orange came out with a tester a few years ago.


$500 US. Not cheap, but not horrible either if you have a drawer full of tubes (like i do). I'll be keeping my eyes open for a good sale.


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## Alex (Feb 11, 2006)

davetcan said:


> $500 US. Not cheap, but not horrible either if you have a drawer full of tubes (like i do). I'll be keeping my eyes open for a good sale.


I thought they were around $350 when they came out. I came close to buying one but I've never kept an amp long enough for a tube to fail . My Matchless is actually pretty easy for changing the EL84's and does not require any biasing.


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## davetcan (Feb 27, 2006)

Alex said:


> I thought they were around $350 when they came out. I came close to buying one but I've never kept an amp long enough for a tube to fail . My Matchless is actually pretty easy for changing the EL84's and does not require any biasing.


They have that covered with this apparently. Almost sounds too good to be true 

Around $450 US

DIVO OV4 Self Fit Kit – Orange Amps


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## davetcan (Feb 27, 2006)

VHT Amp - Tube Tester 2

$100 US


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## Alex (Feb 11, 2006)

davetcan said:


> VHT Amp - Tube Tester 2
> 
> $100 US


Seems like a good option


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## aC2rs (Jul 9, 2007)

The Orange VT1000 is _very_ cool!
It looks like it would be a perfect option for testing tubes at home - just not inexpensive.


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## aC2rs (Jul 9, 2007)

The VHT Amp Tube Tester 2 looks interesting as well.
It tests the tubes in the amp but only does power tubes.


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## dwagar (Mar 6, 2006)

I have one of these old guys at home


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## epis (Feb 25, 2012)

davetcan said:


> VHT Amp - Tube Tester 2
> 
> $100 US


That's simple bias meter, not a tube tester.


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## davetcan (Feb 27, 2006)

epis said:


> That's simple bias meter, not a tube tester.


"The VHT Tube Tester 2 provides two completely independent current-measuring tube tester sections. Simply plug your tubes into the adapters and then plug the included 8-pin octal-based adapters into your amp. The two high-quality analog milliamp meters measure the tubeʼs cathode current. You can use these measurements to observe your tubeʼs real-time dynamic performance, see how well theyʼre matched, adjust the bias, monitor your tubeʼs performance as they age, check for unstable conditions, and more. Additional test-pin jacks are provided for precise digital multi-meter measurements and analog meter calibration. The VHT Tube Tester 2 is an affordable bench and road tool that lets you see how your output tubes are performing in real time, and whether itʼs time for replacement or a bias adjustment, etc. Get the most from you tubes — and amplifier — with a VHT Tube Tester 2."


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## epis (Feb 25, 2012)

Meh, you can do it with any bias meter. Simply that's bias meter simplest as it can be


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## davetcan (Feb 27, 2006)

epis said:


> Meh, you can do it with any bias meter. Simply that's bias meter simplest as it can be


So what exactly will a full blown tube tester do that is any different? Hopefully something


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## epis (Feb 25, 2012)

davetcan said:


> So what exactly will a full blown tube tester do that is any different? Hopefully something


Well, tube tester will do emission test - tube life and internal shorts check on different tubes, this device isn't tester, it's just an adapter, tester is actually your amp and its fuse  You can "test" only output tubes in your amp. 
Personally I prefer using my amp as tube tester, but for testing batch of tubes of unknown condition, real tube tester is way to go.
$100 US is to much for something what ordinary $10 multimeter can do.


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## jb welder (Sep 14, 2010)

Yes, that VHT unit is basically 2 bias probes with 2 built in multi-meters.
You can get bias probe kits for fairly cheap and DMM's are pretty cheap too (crappy tire)
(TubeDepot Bias Scout Kit | TubeDepot.com)
But if you're going that route, the VHT doesn't cost that much more and it's ready to go, so it's not a bad deal.
Just to note that they will only fit one particular type of tube socket, so a unit that does 6L6/6V6/EL34 will not do EL84/6BQ5's etc.


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## BSTheTech (Sep 30, 2015)

I've had an eBay alert set for the Orange model for a couple years. I've seen one used one for a decent price and it sold in minutes.


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## Frenchy99 (Oct 15, 2016)

I still use my very old Lafayette Tube tester ! works! its all that counts...


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