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In Reply to: RE: Help Identifying 12AX7 tubes posted by lehmanhill on September 23, 2020 at 08:55:37
I wouldn't have told you it was a Tung-Sol unless I was sure it was a Tung-Sol!
Also 322 is the EIA code for Tung-Sol.
Finally the getter shape is typical of early production Tung-Sols. Later tubes had round getters. The fact that your tube is a 12AX7 (not a 12AX7A) and that it has a square/rectangular getter simply means it is an early production tube. The fact that it is on an angle is just the way they made it in some of their early tubes.
If the tube has a 4 digit code after the "322" you can decipher the date of manufacture - the first two numbers are the calendar year and the second two are the week. For example 5922 would mean the 22nd week of 1959.
Follow Ups:
Thank you very much. That answers all of my questions.
I didn't understand that a relabelled tube would have followed the EIA code, but obviously they did. Thank you for being patient with a tube rando like me. I'm learning, but have a long way to go.
Based on your response, my tubes have a date code showing the 35th week of 1956 which is appropriate because the Philbrick K2-W started production sometime in 1952.
Yes the manufactring codes can be tricky to figure out sometimes. I have some tubes that are re-branded to one manufacturer and are actually another. GE and Sylvania did this on more than one occasion. The trick that Jim mentioned is finding the code. IIRC GE is "188", Sylvania is "312", RCA is "274", Raytheon is "280". Again I could be off on my numbering, but somewhere online is a tube manufactring ID chart.
Thanks, Sam. I am learning, but there is so much to know. I don't have a current use for 12AX7, but I seem to keep adding tube gear over time, so I will keep them for sentimental value and with the hope of hearing them in the future.
Jac
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