#40 Electronic Tutorial: How to test an electron tube / valve without a tube tester

What can be done if you are in the need to test a vacuum tube but you do not have a tube tester.
PLEASE SAFETY FIRST!
USE A ISOLATION TRANSFORMER!!

[@dinosworkshop6870]

An absolutely excellent video. Safety first!!! I like the hands on testing. I never saw how to test like this before without a tube tester. This video is super helpful. Added to my favorites. thanks much for this concise tutorial..

[@TRXLab]

Satellite_Guy Thank you so much! Always good to hear from you :-)

[@lyntonprescott3412]

Fantastic video Peter. Great explanation which makes the operation of a valve easier to understand, especially to a novice like myself. I will have to give this test a miss on my bench, I don’t think my pacemaker would like 200 volts DC! 73’s Lynton.

[@Millstone_Firewood]

Very good video. I'm slowly working my way through all your videos and learning a great deal. Thanks very much. Keep the electronics tutorials coming! Mitch

[@TRXLab]

+Mitchell Smith (KB3GKC) Hi Mitchell, thanks for feed-back. I'm glad that you like my videos! 73's

[@Guyjami]

Great explanation, very clear and helpfull to understand how a tube is working. I've a few tubes to test so where can i find the reference cards ? Thank's a lot.

[@rene46biard]

This explanation using tubes and how to test them is so good !!

[@Michlag]

Very nice video... What power rating has that pot between anode and screen grid?

[@cassvirgillo3395]

Hi TRXBench, Peter, Excellent Demonstration and explanation. A fellow KZbinr suggested your channel, and, I am so glad he did, am now a happy subscriber. Take care, be good, C.

[@TRXLab]

Hi Cass, thanks for watching and subscribing! All the best and Cheers

[@karlfell3768]

Always preffered good old solid state electronics, not enough room in my small lab to play with the high voltages of tubes but a very informative video as always. Keep up the good work.. Karl.

[@TRXLab]

Karl Fell Hi Karl thanks for feed-back. This test should only be carried out in a despaired need if there is no other way. So no standard test :-)

[@tubeDude48]

Slick simple Tube Tester.

[@Rev22-21]

Excellent video and instructions.

[@sheresound]

Hi, interesting and well explained video, thanks. I have a question: can that old tube tester (Funke w19) also test 6L6 tubes?

[@TRXLab]

Yes no problem

[@sheresound]

Interesting video,how many Watts can dissipate the 3k potentiometer you used? Thank you

[@technos123]

Another great video and very interesting to watch. I do not have an isolation transformer so best for me to just to watch over your shoulder. However still fascinating to watch and a great way to learn.

[@TRXLab]

technos123 Hi, may be the isolation transformer is a good idea for a gift.... Thanks for watching and feed back!

[@jimmy8653]

Great work Peter

[@duowienermelange]

Lets assume we have an additional signal generator and a 2 channel digi-oscilloscope. If we drive the g1 with a sine wave from the generator and connect the 2 osci channels properly, wouldn't it be possible to measure the characteristic curve of the tube?

[@gvvq-pi5ml]

Hi there very good video yet again, I have to say the G is standing for GRID on a tube and not GATE, think GATE is for a FET or MOSFET Grid is for Valve...thank you Fred in England.

[@TRXLab]

Tom Smith Hi Fred, thanks puhh my bad English... yes of course GRID. Thanks for helping out.

[@CharlieTechie]

g4vvq1983 Don't apologize for your English, much better than my German, which I can't speak at all. 😀 Very nice video, lots of good information. I am building a stand alone test apparatus for testing pre 1920's and transmitting tubes, so thanks for all the ideas you have provided.

[@peheinz4358]

Sehr gut erklärte Vorgehensweise, ganz besonders der Anfang des Video ist super! Man kann halt nicht oft genug darauf hinweisen das man es bei solchen Aktivitäten mit absoluter Hochspannung zu tun hat, mit sowas ist wahrlich nicht zu spaßen und kann im schlimmsten Fall sehr böse enden!

[@TRXLab]

+peheinz vielen Dank für die Rückmeldung und fürs schauen meiner Videos! Der Umgang mit Strom kann in diesem Fall schnell tödlich enden. Deshalb ist es wichtig das man genau weiß was man tut!!

[@oliverjames4442]

This is a very good tutorial well done TRXbench. I would like to carry this test on an output valve of a 1938 valve radio however I do not know the parameters to set up my test. The valve in question is an AL4 (output pentode). Can you help me in finding the setting parameters for this valve?.Thanks again.

[@TRXLab]

Oliver James Hi Oliver, well the AL4 is equal to the AL3 . If you send me you email I can give you what I have...

[@budleyca1]

This was a great demonstration and excellent video, tnx for sharing... Bud...

[@TRXLab]

budleyca1 Thanks buddy!

[@ketutwiadnyana2610]

Hmm I am just thinking, can you current limit the filament current to say, 0.8A, and voltage limit it to 6.3V before plugging in the filament? That way, you will not stress the filament on first power up.

[@mariocatena7220]

Hi, very good video and great details, could you share the Max Funke tube tester EL34 card? Thank you

[@TRXLab]

time is very short sorry

[@thorkildgerstrm887]

Good video, thanks. After reading all the comments and after looking around on the net, I am not sure where to get the test card data information. Of course I can easily get the datasheets, but from my point of view, datasheets and Max Funkes test cards are two different things. I am looking for test card data for KT88 Electro Harmonics. Any idea where to get it?

[@jan-thorehol4786]

Thanks for a interesting video. I think you maybe have some error in the schematic? You have the voltmeters for anode and grid in series, I think? You should perhaps have a ground point between? This is a emission tester, I suppose? Could you do something to make it an transconductance tester? Also, if you dont have the "cheatcards", maybe use some old tubebooks or info on the web? I would like to emulate this method, but with a regulated power supply for the high voltage. And go for 6v dc on the heater... Anyways, stirring stuff, keep up the good work!

[@CharlieTechie]

I believe it is assumed that where all the lower connections are made would be the common (ground) point and that is where the negative power supply connections would terminate. I also believe he is using the upside down T to indicate the common or ground point. Then the volt meters would be able to measure the voltage from the high point to the low point of the circuit. The current meters are in series and would measure the current flow to the plate and Grid-2. Hope that helps.

[@jan-thorehol4786]

I was thinking the same, Chuck. But I just pointed to some points for clarification.

[@jan-thorehol4786]

By closer lock, I see that the schematic indeed is correct and that the ground is where it should be. Sorry about my silliness. I am myself looking into building a modern dynamic mutual conductance valve tester, so this is a interesting step towards that. Also my point about using 6v dc for heating does not work as well for this application. 6.3v dc (or ac) is correct.

[@TRXLab]

Looks like all is clear now. Thanks for watching and comment..Cheers

[@das250250]

So i assume in circuit: under normal circumstances operation g2 is the output and in this test we tie down g2 midway in this test to work out the drive current (base leg of a transistor) in g1 ? So ordinarily when we vary g1 current we vary the large g2 voltage and hence amplification ?

[@Cybergonzo1]

Is there also a german version of this video or german subtitle ? I am really sad about understanding nothing, because a german doesn't speak german.

[@tubes_oldtubes_old]

Good explanations, nice lab. But who work with tubes and knows them can easily imagine this kind of test and who can not imagine is in danger to be electrocuted. I use stabilized voltage suply, one for each voltage needed (plate, screen, g1 and filament).

[@mrbambix]

Hi, first off I really enjoy your videos. Can I ask a question? I see you use an isolation transformer on lots of projects and crank up the voltage slowly. Can you tell me exactly what you are using for this process ? Thank you and regards, Leo

[@mrbambix]

Let me rephrase i can see the very expensive isolation tranformer you are using but can you suggest a more budget option for this ?

[@TRXLab]

Hi Leo, well there is not really a budget solution. Certified isolation transformers are expensive. You should buy one off ebay that might be the only way. But be careful not all transformers are isolation transformers even when they called so....

[@mrbambix]

Thank you for your reply much appreciated. Well i will try look around. For all my other testing on non tube applicances I usually use my lab power supply to slowly crank up the power but I can see that will not really do for tube based circuitry really. Regards and again much appreciation for your videos. Leo

[@whatspapadoingnow6197]

I am wondering if you could tell me what the value of the large variable resistor (POT) you are using to control the screen voltage? Thanks for the video.

[@TRXLab]

If I remember right it was 3KOhm

[@michak9265]

@@TRXLab , I am actually quite confused about this pot. As I can see you're using something more powerful here. If we calculate its power loss it turns out to be 13Watts! I was wondering if it is possible to use something like 4,7k, 10k or even more here?

[@djkamilo66]

this video is amazing, it helped me a lot, but i still cant find the tes velues you have on these card anywhere and ive searched a lot. could you scan some of those cards? values for 6l6, 6v6, el34, 84, 12a-7 would help or if you know where i could find those. thank you so much.

[@TRXLab]

Camilo Pasin Thanks for feed-back Camilo! I need your e-mail....

[@djkamilo66]

i found ones but there is some missing for me, speacialy 12au7. my email is [e-mail]. thank you.

[@oliverisailovic]

Hi friend! Thank you for beautiful video! Can I use same or similar procedure and circuit for testing 6L6 tubes?

[@tubes_oldtubes_old]

Of course yon can test 6L6, read datasheet fot voltages and results. In fact a tube tester is doing same tests but a little easier. I am doing frecvently such tests at tubes, even I have a tube tester L3-3.

[@oliverisailovic]

Thank you friend!

[@Lenny8679205]

Great video! I have a question, I'm working on a Nordmende Boheme radio and the EL84 output tube runs very hot 420 F after 5 minuets and the audio gets distorted. The radio has been recapped and out of tolerance resistors replaced. My tube tester shows the tube as good with no shorts. Tube voltages are: Schematic: pin 7, 240V pin 3, 8V pin 2, 0V pin 9, 250V Measured voltage: pin 7, 250V pin 3, 7.6V pin 2, .08V pin 9, 232V Is this voltage difference enough to make this tube get so hot and cause distortion?

[@TRXLab]

+Len S Hi Lens, no if you have taken all this measurements without a mistake it can't be the reason. Normally I would see a couple capacitor as root cause but you are saying that all caps has been replaced...Very often it happens that something went wrong with the recapping so double check it. Beside that there might be a problem with the output transformer or a problem in the power supply. Have you checked the ripple?? But anyway can't really advice you per remote the problem can be anywhere...sorry Cheers

[@Lenny8679205]

Thanks TRX I will check my work again and check that output trans. I have no way of checking the ripple.

[@dennisqwertyuiop]

excellent video thanks for doing a a setup

[@TRXLab]

***** Thanks for feed-back Dennis!

[@oliverisailovic]

Thank you so mach for great video and education!

[@TRXLab]

Thanks for watching Oliver Cheers

[@oliverisailovic]

Hi friend! Can I use same procedure and circuit for testing 6L6 tubes? My email is [e-mail]

[@oliverisailovic]

Hi friend! Can I use same or similar procedure and circuit for testing 6L6 tubes?

[@AtomicElectronCo]

So, could you recommend a good site for downloading the tube "reference testing cards" or whatever they are? Thank you.

[@nobytes2]

MAN CAVE NO.1 Just Google the tube model followed by datasheet. They are called datasheets.

[@iw0hex]

Thanks for excellent video, very nice to learn how it's possibile to test a tube. You are great :-)))

[@TRXLab]

Pasquale IW0HEX Hi Pasquale, yeah this application is very helpful if there is no other way. Thanks for your comment buddy.

[@robertvaldimarsson2109]

Sehr schönes, hilfreiches und gut erklärtes Video. Vielen Dank :)

[@TRXLab]

+Róbert Valdimarsson Hi Robert, vielen Dank!

[@nikoladivic2786]

Super Lehrer.Danke schon.

[@TRXLab]

Freue mich das es gefallen hat Nikola! Alles Gute

[@erin19030]

I use this method, however I built a permanent test jig chassis.

[@inthenameofjustice8811]

How can I get into electronics without having to go into debt for twenty years in student loans and without having to then buy £30.000 worth of test equipment? Am I just left checking fuses?

[@TRXLab]

InTheNameOfJustice Hi George, no I don't think so there is much more left than fuses:-) Additional to that 80% off all repairs can be managed by a simple DMM. Beside that there is a huge surplus market where you can buy really valuable test equipment on a budget. Regarding skills, I think you are doing exactly the right. You are interested in electronics and step by step you are getting better. If you are not a member of the UK radio association (HAM radio club) yet, then it is now the moment to join. There is really a huge knowledge base among the Ham radio operators and they are really willing to help and teach. So do not look to much at the black side... Have fun :-)

[@johnc8910]

A really good basic book for simple to pretty advance electronics is the ARRL Radio Amateur's Handbook. About $40. Your library should have a copy for you to look at. It's oriented toward communications, but it is a good, practical book. Also covers basic to intermediate test equipment.

[@ichbins1729]

Daumen hoch, auch wenn es LEIDER in englisch ist. Solche Grundlagenvideos hätte ich dann doch lieber in Deutsch und ohne Wortfindungsstörungen, sorry 😂🤣 andererseits hat es für mich den Vorteil, dass meine lahmen grauen Zellen in den Pausen beim übersetzen wieder aufholen können.....

[@TRXLab]

HaHa ja richtig. Danke fürs zuschauen. Hier haben wir ja dann beide was gewonnen, du kannst deine grauen Zellen trainieren und ich arbeite durch ständige Praxis an meiner Wortfindungsstörung. Da nennt man win/win

[@erin19030]

I watched your video carefully , however I digress and take to disagree with your method. The transconductance of a vacuum tube is the element factor of a valve's strength and whether it is any good or not. I use the same method you do. Your method however did not come up with a value for conductance, i.e. transconductance. Your method used is merely a go- no-go test. The 27 ma.that You measured was the quiescent value of the valve at rest or cutoff. Then you measure a current of 33 ma. at zero bias. Transconductance GM = the change in plate current divided by the change in grid voltage. By the values given I come up with 3,000 micro-mhos. The maximum value is 11,700 micro-mhos. Thus making the value of 3,000 way below a passing value for a good tube.

[@Jaantoenen]

Too patronizing with the safety. A disclaimer would have sufficed.

[@DeeegerD]

200v? Easier to get a tester lol.

[@TRXLab]

in the us okay that is a point lol

[@CharlieTechie]

Digger D Hard to find tube testers for very old tubes (pre 1920's) and transmitter tubes, so it does have a place. But agree, tube tester is faster if available.

[@rodieselpower]

This tutorial is for much one the most accurate option that anyone has to do the test... pretty long video thou... :P

[@TRXLab]

René Ortíz Hi Rene, thanks for comment, but I'm not completely sure what you mean..

[@rodieselpower]

... what I mean is that you are giving enough info about how to do a proper test without risking yourself with a fatal discharge and without risking your device and so on. Nice work.

[@TRXLab]

René Ortíz Ah okay, now I understand your point :-) Thanks a lot

[@valvoxvo2755]

stupid test

[@paulwolters3452]

Beautiful video,thanks very much, this is very helpfull, so I say once more thanks very much (nice lab by the way, liked it very much), i am bilding a otl at the moment and have no tube tester, so i will try this. Greetings from the Netherlands Paul.(sorry my englihs is very bad, hopefully you can read this.), i will be carefully.