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ID = 50769
United States of America (USA)
Brand: Moorhead Laboratories (Pacific); San Francisco
Developer: Moorhead Laboratories (Pacific); San Francisco 
Tube type:  Triode, vacuum   Universal 
  <1925 rare.
Identical to A_Moorhead-spherical
Similar Tubes
Other shape (e.g. bulb type):
Normally replaceable-slightly different:
First year 1919 Saga of the Vacuumtube, Tyne page 172.

Base UV-Base (4 Pins+Bayonet, USA 1914 WE)
Was used by Radio/TV-reception etc.
Filament Vf 4 Volts / If 0.7 Ampere / Direct / Battery =
Description Moorhead/Marconi/DF Type A: The Type A is a hard tube also known as the Marconi VT Class II. Some have Class II marked on the base rather than A on the bulb. See also the cylindrical version. Tyne does not publish about this spherical version. But Tyne describes the cylindrical version: drawn tungsten wire filament, the eleven-turn spiral of nickel-wire-grid and the nickel sheet plate, rolled into a cylinder about 3/4 inch in diameter. It operates for 60 to 90 volts. Technically it is more or less a SE-1444. See also type B, C, D, E, F and G. See Tyne page 172 and 173.

Family - according to Tyne: Type A is similar to SE-1444, also with hard vacuum for amplification. Type B is a similar tube, but with a low vacuum for operation as a detector with 18-40 volts on the anode. Type C is similar to Type A, except that the grid is constructed of 22 turns of molybdenum wire with a pitch of 0.3 inch, instead of nickel - and for anode voltages of 80 - 500 volts. Type D is the unbased Electron Relay (ER) previously made by Moorhead. Type E is the British standard Type R, similar to Type A, but with spherical bulb and European standard four-pin base. Type F is similar to Type E, but with a low vacuum like the Type B. Type G is similar to Type C, but has a spherical bulb and an European standard four-pin base. It is the same as the British standard Type B tube. 
A_Moorhead-spherical: own collection
Peter den Boer


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