The EBF2 is a double diode pentode designed for use in low cost broadcast receivers. This exhibit has the Mullard late 1930s bright red metalising and is unused.
The valve is a high impedance variable μ pentode, with two auxiliary diodes all sharing a common cathode. In a superhet receiver one diode would be used for signal detection and the other to produce an AGC voltage to reduce the receiver sensitivity on strong signals and thus prevent overloading and distortion. The vari-μ pentode voltage amplifier in a low cost receiver would be the IF amplifier. The attached data-sheet gives such a use for the valve.
The classic envelope is 29 mm in diameter and, excluding the Ct8 base pins, is 85 mm tall.
References: Datasheet & 1043. Type EBF2 was first introduced in 1938.
Absolute Maximum Operating Conditions¶
Updated April 09, 2020. shape:classic construction:pinch type:double.diode.pentode age:1930.1940 base:ct8 heater:6.3v pins:8 pin:1.m pin:2.h pin:3.h pin:4.k pin:5.a(d1) pin:6.a(d2) pin:7.g2 pin:8.a pin:tc.g1