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Help Identifying a Tube - Westinghouse 12AX7A

jisadore

Member
2013-02-22 4:16 am
I recently bought an amp and it had Westinghouse 12AX7As in it. I've been trying to find some reliable information on them and it is a little hard to come by. I have a suspicion that they might be rebranded knockoffs, but there is a very similar looking one on eBay for quite a lot of money. Any insight into these tubes would be appreciated.

http://www.flickr.com/photos/isadore1/8495718987/
 

Parafeed813

Member
2012-08-15 8:24 am
Wondering why the Chinese put that shield there.
I don't know any other ECC83/12AX7 with a construction like that.
Considering that they are copyists, they must have had some inspiration (example)?
The ECC808 is like an ECC83 with a shield, but not one that wraps around the plates.
 
the Chinese examples are copies of 6n2p whit changed heater connections.
the first chinese tube factories where set up whit western help, the later whit russian technology.

the 6n2p is a noval replacement for the octal 6sl7 in Newly designed equiptment.

the chinese 12ax7 will have comparable gain to a 6n2p:80 instead of 100

Midnightmayhem: They look genuine. Made in Germany is generally good. I would keep them rather than sell. Also sometimes people list things on eBay for outrageous prices hoping someone will bite. If they test good I'd run them.

you sir, made me laugh my *** off :D

except for the diamond marks, and Fat bulbs slim short plates(RFT) http://www.tubemongerlib.com/galler...83+12AX7+Tubes+Foil+Getter+-+East+Germany.jpg

here's a nice rule of thumb, if the inside connections are copper, its made by communists
 
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JRGuitarGuy

Banned
2012-10-09 11:25 am
Okay maybe someone more knowledgeable than me can shed some light on the difference between the As and Bs Chinese/Shuguangs 12AX7s?. I have some that are labeled the Bs and they have this badass mid range grind like no other, really gainy more so than my JJecc83. I think the Bs are 9th gen designated and I have read and heard the As were 8th gen, is really any difference at all? and I seen there is actually a C version is it even more gainy?
 
Lettering looks genuine upon further inspection the inside looks nothing like any of my german or usa made tubes. It does infact look like a chinese tube I once saw... Who has the time to strip and repaint cheap tubes? Or did they make them that way? I would say that it is probably worth about ten bucks if it works and someone with ten bucks needs it.
Also there are lots of websites dedicated to preamp tube identification. Apparently the lettering on the outside is not nearly as telling as the structure inside. When you get a good collection going you will be able to Id tubes without any paint at all. I did not look closely at the pic the first time I'm eating my words...
 
It is correct, these are fakes.
I know most of the german small signal triodes - none look like this

here's a nice rule of thumb, if the inside connections are copper, its made by communists

correct !

Here are a few other communist-tube characteristics:

  • shiny, smaller nickel pins with sharp ends (except german democratic republic(GDR), those aren't shiny but sharp and pointed (WF, RFT, Funkwerk Erfurt))
  • the glass nipple on top is small, sharp and more fragile (except GDR)
  • the micas aren't shaped as usual like a star but more like a 4-edged-trochoid (except GDR and Hungary (Tungsram))
  • the system which holds the getter is not shaped as a circle or a "D", but more like a dish or pan.
  • From time to time you can hear "здоро́вье!" in your speakers


Interesting. I have not thought of that before. Did they have better accesss to copper than the nickel alloys used in the West?

No, just different technology. Soviets were particularly good in terms of metallurgy. Glass-metal-bonds/seals are a rather complex issue and different countries have developed different technologies.
Western countries use(d) a molybdenium-nickel-alloy whereas the soviets use(d) copper with a layer of copper(I)-oxide. The copper oxide is the link between the ion-binding in the glass matrix and the binding with metallic copper. Remember, copper(I)-oxide is semiconductor ! (direct bandgab - 2ev) [wrote ma last solid-state-physics exam today :D] So the binding to the metallic copper isn't weak as with other oxides. So the color is not due to copper, but because of the even more red colored CU2O
Early rectifiers were built with this Cu2O: Metal rectifier - Wikipedia, the free encyclopedia

Some facts on glass-metal-seals are here: Glass-to-metal seal - Wikipedia, the free encyclopedia

A bit more advanced: http://downloads.hindawi.com/journals/apec/1975/509270.pdf

Hope that cleared things up a bit.
 
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No, just different technology. Soviets were particularly good in terms of metallurgy. Glass-metal-bonds/seals are a rather complex issue and different countries have developed different technologies.
Western countries use(d) a molybdenium-nickel-alloy whereas the soviets use(d) copper with a layer of copper(I)-oxide. The copper oxide is the link between the ion-binding in the glass matrix and the binding with metallic copper. Remember, copper(I)-oxide is semiconductor ! (direct bandgab - 2ev) [wrote ma last solid-state-physics exam today :D] So the binding to the metallic copper isn't weak as with other oxides. So the color is not due to copper, but because of the even more red colored CU2O

Hope that cleared things up a bit.

the russians likely used a full lenght of dumet wire for the seals and connections. as the welds to the thicker tube pins and the molybdenum-nickel. this increases the number of welds. they likely encountered problems whit welding the Three metals successfully.

in any case, its a stroke of genius. only using two sorts of metals simplifies production.

v4lve.