The EF39 was described by Mullard as a variable-mu RF pentode, with sliding screen characteristics, for use as a controlled RF or IF amplifier. The EF9 is electrically identical to the EF39 but is on a Ct8 base. The frequency range of operation would be up to 30 MHz.The envelope carries the Pentone trade mark.The Cossor OM6 is directly equal.![](../pics/aaq0426a.jpg)
The reverse is plain red coloured zinc paint.The classic envelope is 30 mm in diameter and excluding the IO base pins it is 85 mm long.References: Data-sheet, 1040 & 1043. Type EF39 was first introduced in 1939. See also 1939 adverts. |