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by fuzzfactor
5 days ago
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You may still be able to buy the prefabricated mass-produced tube bases for regular 9-pin miniature tubes. These are just "wafers" of glass a few mm thick with the 9 metal pins through them. Both having matched expansion characteristics that were improved over a period of decades. The base is held in a jig, the inner electrode assembly is tacked onto the proper pins at each point. Then the tough borosilicate glass tubing is lowered and sealed to the wafer. Evacuation is from the top, and then that is sealed to a point like you see on any ordinary 12AX7-sized tube. |
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