How much are these tubes worth?

How do they test? A Ferrari 328 with 200,000 miles on it is probably worth a bit less than one with 2000 miles on it. 

Don't smudge the paint on the tubes!

It’s interesting I live in Oregon and see a lot of Tektronics scopes and test gear. A lot of the dual triodes that come out of these pieces no longer show a match between the two triodes as they had differing loads on them.

noromance1,619 posts01-04-2019 4:16pm

Don’t smudge the paint on the tubes!

+1

@ baseben9

Don’t even attempt to wipe them off. Keep your oily fingers off the white labeling.
Their value? You need to have them tested.

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Telefunken 12AX7 that test new are probably worth $125 and up, depending on the cosmetic condition, how closely matched the triodes are (2 triodes per tube), how much over new they test, etc.  If they test below new, the price drops rapidly.

Also- check between the pins for a diamond, molded into the glass envelope’s bottom. Some other companies manufactured tubes for Telefunken. Those with diamonds are worth more, if they test well, as mentioned above. Some of the smooth plate Teles are quite rare/desirable. You may have struck gold! https://www.tubedepot.com/products/telefunken-ecc83-12ax7-smooth-plate Lots of info here, regarding the variants from Tele: http://www.audiotubes.com/12ax7.htm

The price I quoted above was for the pair of Teles.  Look them up on ebay there are plenty for sale there.

Most old production 12ax7's test as new, or near new, until they immediately test as well used (same with old production 5ar4's).

Testers used (over the years) have been a 539C and 2 TV7's.

Difficult tubes to test, though as somewhat mentioned balanced sections are a must if required by the circuit it's used in.