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The DE3 is a dull emitter triode from 1924 and this exhibit is an early example. Later production used a moulded Bakelite base. M-OV sold the DE3 under both the Marconi and Osram brand names. This exhibit has the Marconi name.

The filament is rated at 2.8 Volts at 0.06 Amps, this suggests two dry cells in series as the filament supply, but in fact a 4.5 Volt 'bell' battery would be used with a series rheostat. The filament could thus be maintained at the 'correct' voltage. The valve can be used at LF or HF or as a detector according to the label.

The obscured construction is of a vertical anode 18 mm long and 5 mm diameter, into which the grid and filament fit co-axially. The filament is a single strand, and the grid is a fine wire helix supported on a side rod through the whole length of the anode.

Thanks to Joe Gruber for sending the images.

The wide glass tube envelope is 25 mm in diameter and, excluding the B4 base pins, is 95 mm tall.

References: Data-sheet, ⁴⁰⁵¹ & ¹⁰⁰³ Type DE3 was first introduced in 1924. See also 1924 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

PDF scanned from an original document held by the museum