1946 HMV 1804.

[Geordie McBoyne]

Another one of the original valves has been substituted with another type. The vision demodulator diode in the 1804 should be a Marconi-Osram type D43. This is a largish signal diode on the B5 base, it has a 4volt heater. Top cap anode connection. It has been replaced by a D63/6H6 octal base double diode, 6.3volt heater.
http://www.radiomuseum.org/tubes/tube_d43.html
http://www.radiomuseum.org/tubes/tube_d63.html

Geordie McBoyne.