I am working on an amplifier for a friend which appears to be in need of a
pair of Svetlana 4CX800A tetrodes. The amp was damaged in shipping and the
tubes were found dislodged in their silicone rubber chimneys, complete with
bent pins.
Question: Is it generally necessary to replace these as a matched pair? I
measure a high DC resistance between the cathode and filament on one of the
tubes and I suspect that as these two elements warm up with filament voltage
applied, the cathode becomes closer to the filament, thus making the
resistance even lower. Does anyone know the approximate spacing between the
cathode and filament? Thanks!
-Paul, W9AC
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