How to distinguish tube types

[Carlman]

I have a box of tubes, mainly 6DJ8's but a few others.  My preamp only likes 12AX7's... and right now the tubes for it are being cryo'd.  So, I got to thinking... I wonder if any of these old tubes would work?  But, I can't tell what they are.  I have 2 Russian tubes (I'm basing this on the fact that there is a Soviet star on them) that have '79' on them... and another pair that have no markings at all.

How do you know?  Any good guides out there to identify tubes?

Thanks,
Carl

[richidoo]

They can vary in look by mfg, but the pinouts of the different 12V types are the same, but they are not interchangeable.

You should be able to see the markings and see if your tubes are knock off of 12AX7. This is a rundown of 12AX7 variants and all their weird names:
http://www.audiotubes.com/12ax7.htm

Other tube types are described on the parent page:
http://www.audiotubes.com/bjlinks.htm

You can find a lot of pictures of tubes on Ebay, no guarantee they are accurate though!!  

The markings, if genuine is your best guide to what you have, not the pictures, because glass can vary but circuit inside is same. Glass and pins are identical on most of the 12 series. Markings can be wiped and repainted to make forgery because some of these tubes are worth $500^. But I assume you've used these before and know they are real.

If you have some strays that you don't know what they are, I know someone who can ID them for you by testing. Actually I bet Steve can do it with that awesome tube tester he has!!

Tell me if you see a bright flash!  

haha
Rich

[Carlman]

If you have some strays that you don't know what they are, I know someone who can ID them for you by testing. Actually I bet Steve can do it with that awesome tube tester he has!!

This is exactly my situation... I sent off my good tubes to have Cryo'd and I'm holding the oddballs that I couldn't identify.  I greatly appreciate the links and explanation... and for letting me know what I suspected... I need to test them.  It'd be nice to see how my tubes measure anyway and match up the best pairs.

I came across a nice set of Siemens in my digging that I'm having cryo'd also.... I'll be excited to hear those.  But, until the cryo batch gets done, I'm preampless for a few weeks... That is, unless I learn that I have some 12AX7's...

Thanks again... now I can grovel for testing.

-C

[stereofool]

Carl,

I do have a Hickock 539B tube tester...which I'm embarassed to say   ...that I haven't used it in such a long time...I'd have to bone up on using it again.

I've got boxes of tubes that I need to go through...one of these days    !

You are certainly welcome to 'play' with it sometime, though.

I guess this is another reason I need to get off my butt and get things finished, around the house   !

[lonewolfny42]

Carl.....
Where did you send the tube's to be cryo'd ?

[Carlman]

Chris, I'm using my Canadian Connection...

I do have a Hickock 539B tube tester...which I'm embarassed to say   ...that I haven't used it in such a long time...I'd have to bone up on using it again.

Wow... that's cool.  I know nothing about how tubes work.  I read about it a long time ago... and why resistors replaced them but it's been too long to remember why/how they work.  I have to fully understand it to 'get it' unfortunately.  I think that'd take a lot longer than just waiting for my tubes to come home.  However, I greatly appreciate the offer to learn something.

-Carl

[richidoo]

Careful!! Like me with analog, you are tetering close to the event horizon of the great thermionic black hole...

Ooooooo, triode spagettification feels soooo good!    
Black Holes

[tanchiro58]

Hi Carl,

Look at the shape inside the tubes like getters... to compare. I believe 6922 looks more different than 12AX7 or 12aT7. Good luck.

Tan