Sensibly equivalent¶ to:
The DN143 is a double diode audio output pentode, and very few were designed. This valve, labelled as Marconi, is also marked as supplied by Mullard, and so is identical to the EBL21.
The valve has a common cathode and the diodes are for signal rectification for detector or AGC service. We have not found any designs using this early example of all glass construction. It is probable that it was intended as a single valve detector and audio stage driving the output transformer and loudspeaker. It would have needed considerable drive at intermediate frequency and the output pentode is of high gain.
The wide glass tube envelope is 32 mm in diameter. This appears to be standard for Mullard B8B production. The length excluding pins is 76 mm.
References: Datasheet, 1040 & 3002. Type DN143 was first introduced in 1947.
Absolute Maximum Operating Conditions¶
Updated January 26, 2013.