Telefunken EVN171

Telefunken EVN-171
The Telefunken EVN171 tube was introduced early in WW-I, and was used extensively by the German military.  It was a triode, intended for use as a low frequency amplifier.  A note that was with the tube when I found it indicated that it had been removed from a captured German U-Boat at the Philadelphia Navy Yard.  The paper label on the base shows September 18, 1917 as its date of manufacture.

The internal structure is very unusual.  The filament is a length of tungsten wire which droops down close to the grid.  The grid is a piece of wire wound into a spiral shape, and the plate is a metal disk just below it.  The metal parts are supported by a beautifully made glass arbor.   It is a very well made tube and, in that sense, it is very typical of early German tubes.  Contrast this tube with the rather crude DeForest CF-185, also from 1917.

Telefunken EVN-171
Telefunken EVN-171

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