Sensibly equivalent¶ to:
The EF9 is a variable μ amplifier pentode and on the envelope is the trade mark Pentone that Mullard introduced in 1928. Our other EF8 is of later production after the Pentone trade mark had ceased to be used.
The variable μ amplifier pentode would be used in the AGC controlled stages of superhet receivers, IF and for HF receivers also RF amplifiers.
The EF9 is electrically identical to the IO based EF39, additionally the EF9 is pin compatible with the EF5 and has a higher voltage gain.
Our exhibit is unused, and has the distinctive red painted Mullard external metalisation screening.
The metal loaded screening paint had partly peeled off but unfortunately the inner structure was hidden by the silvering of the getter.
The classic envelope is 30 mm in diameter and, excluding the Ct8 base pins, is 84 mm tall.
References: Data-sheet, 1040 & 1043. Type EF9 was first introduced in 1938.
Absolute Maximum Operating Conditions¶
Updated December19, 2018. shape:classic construction:pinch type: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.g3 pin:6.- pin:7.g2 pin:8.a pin:tc.g1