How do you test your tubes ?

[slash14]

Hi !

I've just found an old stock of tubes (mainly ECC8x) an I'd like to test them in order to trash the bad ones.
Right now, I've got a small all tubes guitar amp which I use with my ears, looking for strange sounds or microphony but this method is not really precise, depending on my mood :wink:

I took a look at the tubemeters (eBay seems to be the best source for this kind of product) but most of them are old (so I don't have any warranty about their precision, kinda disturbing for a measure instrument) or highly priced.

How do you proceed to test your tubes?
As I mainly have ECC8x tubes to test, I think that a quite simple testbench could be realized but I don't know all the parameters I should test in order to say if a tube is dead or not.

Thanks for your answers.

 

[StephenGiles]

At the moment - I cough!!!
Stephen

 

[Marik]

For many years I had a Hickok 539C tube tester, which is a very fine piece of equipment, but finally sold it. The testers are designed to work with certain B+ voltages under certain bias. I found the best way to test the tube is to put it into a real conditions, i.e. into a circuit and then measure it, and compare to tube graphs and see how they are correlated.

 

[slash14]

If you want to fix (or build) some old measure device (such as tube meter :wink: , take a look at this site :

http://bama.sbc.edu/index.html

 

[adamasd]

Steve Bench has some DIY options for testing tubes.

http://members.aol.com/sbench101/

adam

 

[slash14]

Yes, I found this site too, I'm working on its schematic but I think I'll finally make a dummy circuit to test the tubes as I mainly have ECC8x tubes to test .

 

[PRR]

> all tubes guitar amp which I use with my ears

For audio, this is an excellent technique. Tube-testers will find gross failures, and some tell exact electrical characteristics, but the ear is the only true judge.

I would add a voltmeter on the cathode. Note the average cathode voltage in your amp for all tubes of one type, and be suspicious of any that have unusual voltages.

 

[MikoKensington]

I use an old Eico 666 "Dynamic Conductance Tube and Transistor Tester". Kind of a scary machine. But works well.

 

[kato]

You can probably just walk to your nearest hardware store and use the tube tester there.

 

[fazeka]

First of all, I haven't seen a tube tester in an electronics store (hardware store?) in over 15 years where I live. And it didn't even work at the time! And even if it did, I doubt that it could generate high enough voltages to test tubes for guitar amplifiers, that's for sure. Maybe for TVs, etc.

 

[gyraf]

I use an AVO mk#4 that I found on a local flea markt. The seller insisted it was an instrument to adjust old diesel engines :grin: ..

http://www.jogis-roehrenbude.de/Roehren-Geschichtliches/Roe-Pruefer/Avo_MK_IV/Avo-MK_IV.htm

Very easy to use, gives quite a lot of important specs. And looks good too..

Jakob E.

 

[pstamler]

I use a little Electronic Measurements Corp. (EMC) 213-211 tester for a basic go-nogo, and a homemade jig with signal running through it when I suspect a tube has high distortion. The signal gets recorded into CoolEdit, and I look at a spectral analysis of harmonic distortion.

Peace,
Paul

 

[kato]

i was just kidding about the hardware store.
that was just a funny memory from being a kid and seeing the huge tube testing consoles.

really I test them by sticking them in a guitar amp and listening...

 

[Scodiddly]

I have a small collection of tube testers, but only the little Heathkit emissions tester is trustworthy. Another project is getting one of my mutual conductance testers running accurately, without having a big stock of new tubes for testing.

Generally more critical tests are done in circuit, where possible. That really only comes up where I'm servicing tube equipment and need to narrow the possible problems down, and I've got a compatible circuit for that tube.

 

[jstark]

I actually just found my dad's old Sencore Mighty-Mite V. I've used it to check a few tubes so far. A couple questions:

-What, technically speaking, are the "grid leak" and "emission" tests measuring?

-On the VU meter, in the green "good" ranges, does greater meter deflection indicate a "better" tube? I mean, does a "perfect tube" deflect more than a older tube, or is there a certain unique deflection that each tube should give?

 

[Scodiddly]

[quote author="jstark"]I actually just found my dad's old Sencore Mighty-Mite V. I've used it to check a few tubes so far. A couple questions:

-What, technically speaking, are the "grid leak" and "emission" tests measuring?

-On the VU meter, in the green "good" ranges, does greater meter deflection indicate a "better" tube? I mean, does a "perfect tube" deflect more than a older tube, or is there a certain unique deflection that each tube should give?[/quote]

An emissions tester just warms up the filament and then runs AC through the tube, measuring how much DC comes out the other end. Basic rectification, which does a reasonable job of telling what kind of shape the tube is in. On the big meter, more is better, so older tubes have a lower reading which eventually dips into the "bad" range.

The grid-leak test just looks for whether any of that test current is getting out via a grid, which should only leak a very tiny amount normally.

 

[adrianh]

Slash;
Save yourself some headache.
Use your amp or a little box you rig up.
A tube tester is too much trouble and it does not find bad sounding
audio tubes.

But if you find a good tester that has transconductance like the Hickcok
539 series and it is cheap buy it.
But expect to pay close to $750 for them now.

Use your amp. It is paid for.