Sensibly equivalent¶ to:
The EBF80 is a variable μ amplifier pentode and a pair of signal diodes in the one envelope. Probably this was designed, as was the later EBF89, as final IF amplifier and AM detector. The other diode would provide AGC rectification.
The hole in the screen allows a window through the anode to the grids inside. The outer grid is a wide pitch helix showing that this is a true pentode. The diode anodes are thin metal strips running vertically through the valve and can be seen inside the screen here.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 59 mm tall.
References: Datasheet, 3002 & 1040. Type EBF80 was first introduced in 1950.
Absolute Maximum Operating Conditions¶
Updated February 22, 2015.