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210 HD Onethirty with weird Tube Sylvania ADB 936

I have an 210 HD Onethirty from 1976.
I have a Question to a weird tube.
The sticker inside tells me, that I need a 12AX7A or 7025 tube. So I checked the assembled tube , but its a Sylvania made in USA ADB 936, respectively ADB 639 (depending on how you read the number, top down or bottom up).
Is it a 12AX7 clone or just the wrong tube?
Thanks a lot from Germany

mm210's picture

HMM. I'll have to look

HMM. I'll have to look through a couple of old tube manuals. Don't remember seeing that one. Milspec maybe? Don't know. Are you sure the rest of the numbers just haven't been worn off? That could be just product numbers or something like that and the 12x7a has worn off.


I really appreciate your

I really appreciate your efforts.
Added a picture.
It doesn't seem, that anything is worn off. Clean surface....Weird thing


Hidden Info?

What are the other numbers/letters under the Sylvania logo? They're partially visible on the left side of the picture. Give us another picture showing that please. BTW, it sure looks like a dual triode like a 12AX7 or one of its cousins. 8 pins, short and stout.


There are 9 Pins, not 8.

There are 9 Pins, not 8.
The hidden (green) letters under the Sylvania logo are: "Made in USA"
No hidden Infos ...


Date Code?

My eyes played tricks on me. Sorry I can't be of more help. Info like this is hard to come by. My guess is ADB could be the manufacturing site code and 639 is the date code for 39th week of 1956 or 1966. Still doesn't help identify the tube type. Just curious, how does the amp sound with the mystery tube?


It sounds quite normal, I

It sounds quite normal, I think.

Probably its a 12AX7, I guess. I cant prove it, because there is no hint on the tube.
Most important for me is, that the amp will get no harm from this tube.
Its inside there for years and still working.
So I will let it assembled.
Thanks to all for your efforts.

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