FW4/800 Mullard black ribbed plate directly heated rectifiers CV31 U20 U18

Description

The Mullard FW4/800 is the continuation of the FW4/500 predecessor.

They share some things in common, the voltage filament but the FW4/800 has a reservoir capacitance of 4uF  thus making it a very versatile valve able to cope with high voltage plate and keeping plate cooler than any similar valve.

We have gathered a set of four pieces. The FW4/800 was first introduced in 1948.