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This was the first EF55 that I have found that was not painted black. It is a joy to see this Mullard valve in the correct red livery.

The EF55 pentode is physically the big brother of the EF50 with which it shares common base connections. The EF55 is a single ended RF pentode with very high mutual conductance and a sharp cut-off. It was designed for video frequency use, probably in RADAR service, and its service code was CV173.

It is an early all glass constructed valve with equi-spaced pins and a spigot for location into the valve-holder.

The current rating places it as a power valve but it is designated for amplifier service with a medium anode impedance.

The outer aluminium shield is 33 mm in diameter. The overall length excluding the B9G base pins, is 80 mm.

References: Data-sheet & ¹⁰⁴⁰ Type EF55 was first introduced in 1946. See also 1946 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.