A few German/Telefunken 12AX7 types I hadn't seen before.

fdejong

Super Member
Pictures 1, 2, 3 These came out of a Fisher TA-800. Branded ultron and labelled W. Germany. Square getter and silver plate bottoms. No diamond on the bottom.

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Pictures 3, 4, 5 Telefunken smooth plate but with four pinch marks on the top. I always though only Mullard/Japanese Mullard had these.

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Possibly siemens or valvo. One guy I bought tubes from said Teles never flash, I don't know if that's true or not, but he seemed very sure.
 
I have/have had many of the "crimped top" smooth plates; that is the final type that they made.
 

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I just got an industrial grade 1966 mullard 6681 12ax7 and it flashes at startup, what is the purpose for this or is it just show? Thanks
 
Smooth are earlier, the flash is typical of Mullards that had the filament hanging down below the cathode tube. The exposed filaments will flash almost white on cold start up, when resistance is lowest.
 
I think Jay nailed it. Or we all read the same wrong info. Low filament resistance when cold. I always wondered why it wasn't a self damaging event. But time proves it wasn't.. I'd also go with Jay on the flash being related to amperex ( amperex mullard) I have some RCA's that say made in england (or possibly great Britain . I'm not looking at them now ) and they flash . I always figured they were a rebrand.
 
Interesting. Are smooth plates generally earlier or later than ribbed? Or is that too simplistic?

The ribbed plates are earlier (1950's-early '60's).
Telefunken date codes are kind of funky and I haven't pinned down when the switch to smooth plates occurred...yet :D
 
I was led to believe the Mullard/Phillips/Valvo filaments flash because they had a different composition or coating/lack of coating....:scratch2:
 
The crimped top says Amperex/Phillips. Phillips made tubes were commonly relabeled as Valvo, Siemens, etc. Probably still nice sounding tubes....
 
I have those teles with the crimp top branded fisher as well, they came in a 63' Futura console.

-Tom
 
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