The DE2LF is a dull emitter triode dating from 1925. It was designed for LF amplification and had a lower anode impedance than the DE2HF released at the same time.. The valves from M-OV of this period used carbonized thoriated tungsten filaments. The carbonizing reduced the effects of any residual gasses in poisoning the thoriated filament.
The second variant of the BBC logo is present on this valve illustrating the fact that this valve is an original 1920s valve, made between 1924 and 1927, and not a later replacement.
The balloon envelope is 32 mm in diameter and, excluding the B4 base pins, is 73 mm tall.
References: 4051 & 1003 Type DE2LF was first introduced in 1925.
Absolute Maximum Operating Conditions¶
PDF scanned from an original document held by the museum
Updated January 24, 2011. shape:balloon construction:pinch type:triode age:1920.1930 base:b4 heater:2.0v pins:4 pin:1.a pin:2.g1 pin:3.f pin:4.f