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TheMooN 13th September 2012 08:48 AM

Mystery Valve ID
 
I would be most grateful for a little sage advice and assistance in identifying this mystery (to me) valve that I picked up somewhere along the line and had filed away in the :boggled: box .

It has been opined that it might be a 12AX7 variant however I remain a little skeptical of this advice !

We have ~ No markings , Chrome box anodes with an additional plate screen running between said anodes , this extra plate also sports ] shaped stabilizer attached to both edges . the additional plate and box anode's are pin attached to a third clear mica ? plate in between the usual top mica and the getter

Said getter , which is a square of foil with a central dish shaped indentation , is supported by a pair of posts .

Possibly a number 2 in the glass between the pins tho rather indistinct unfortunately .

Eastern European production perhaps ? I am fairly sure that this it is not a Tungsram tho .

[IMG]http://i177.photobucket.com/albums/w.../IMG_01241.jpg[/IMG]

bullpeters 13th September 2012 09:24 AM

Geez mate, looks like one of my Chinese 12ax7 equivalents, all those shiny bands within. Completely hopeless advice for you tho, sorry :)

DF96 13th September 2012 10:21 AM

Yes, Chinese. For some reason they include a 'screen' which may have no external connections. At best the screen does nothing. At worst it could pick up a high positive voltage and disrupt things.

TheMooN 13th September 2012 01:50 PM

Thank you gents , I have been reliably directed toward the answer ~ Shuguang 12AX7-A

Being a Far East new production tube numpty I wasn't aware of these .
I must say tho , this peanut money valve isn't performing at all badly in a test-bed pre- amp I am working on atm , quite a nice airy and extended top end !

v4lve lover 13th September 2012 04:08 PM

6n2p-Ev/ER or the Chinese genuine 6n2p whit 6.3v heater between pins 4+5

if you measure resistance between pin 4-5 and 9 its a chinese 6n2p whit Centertapped heater sold as a 12ax7.

V4lve.

DF96 13th September 2012 04:18 PM

Maybe that explains the screen. Does that connect to pin 9 in a normal 6n2p, but left floating for the 'chinese 12AX7' modified version of the design? That means they can use exactly the same tooling for both types, but just change the base wiring: heaters in series instead of parallel, connect heater CT to pin 9 instead of screen.


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