Unknown NOS Tube
- Thread starter thekid777
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pucho812
Well-known member
IS this a joke ???
pucho812
Well-known member
Not at all I am just wondering if you are serious...
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It is probably a twin-triode, possibly in the 12A*7 family, possibly one of the many-many TV Tuner tubes.
Work out the pin-out by following the pins to the electrodes.
Wire a test-socket with 300V of B+, grid grounded, 100K plate resistor, and 1K-10K cathode trimmer. Just cuz it is easy, set Rk to 1.5K and see if plate sits at 210V..... that would be your 12AX7 (see any Fender amp). If you need a larger Rk to get Vp down to 200V-150V, then it is a lower-Mu type. 12AU7 Mu=20 is probably about as low as is likely, plot it to find what it biases at.
Check the other side too, because there are dis-similar dual triodes.
If you are going though grandpa's tubes, ask yourself: are you sure they are good? Many-many old tube men saved their duds, no good reason.
Work out the pin-out by following the pins to the electrodes.
Wire a test-socket with 300V of B+, grid grounded, 100K plate resistor, and 1K-10K cathode trimmer. Just cuz it is easy, set Rk to 1.5K and see if plate sits at 210V..... that would be your 12AX7 (see any Fender amp). If you need a larger Rk to get Vp down to 200V-150V, then it is a lower-Mu type. 12AU7 Mu=20 is probably about as low as is likely, plot it to find what it biases at.
Check the other side too, because there are dis-similar dual triodes.
If you are going though grandpa's tubes, ask yourself: are you sure they are good? Many-many old tube men saved their duds, no good reason.
