Catalogue
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Marconi Radio Valve Type DE3C, by Marconi Company, London, c. 1924
Inventory Number: 20731
Date: c. 1924
Maker Details: Attributed to Marconi-Osram Valves.
Inscription: "MARCONI / VALVE / PATENTED / MADE IN ENGLAND" printed on exterior surface of bulb. "BBC [LOGO] / D.E.3C / FIL 2.8 VOLTS / 1 0 D" printed on exterior surface of bulb.
Size: 110 mm in overall length (including base pins)
Materials: Glass, bakelite, steel, tungsten, assorted metals.
Other Given Number(s): Christie's 215.
Notes:
Marconi Radio Valve (or Tube) DE3C, with silvered glass balloon envelope, polished black bakelite base and four steel B4 base pins. The DE3 was a general-purpose dull emitter triode with a very delicate thoriated tungsten filament rated at 2.8V 0.06A. It was one of the first British valves intended for operation from dry batteries but the battery required was a 4.5V 'bell' battery. This was used with a series rheostat adjusted by the user to provide approximately the correct running voltage across the filament terminals. The device could be used as a LF or HF or as a detector. Construction is a vertical anode with the grid and single strand filament fitted co-axially. The grid is a fine wire helix supported on the side with a rod through the whole length of the anode. The interior surface of the bulb is silvered, probably from use. BBC Stamp ("APPROVED BY POSTMASTER GENERAL") was used from 1st November 1922 until September 1924, and is good indication of date of origin. Previously catalogued with assorted other valves.
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