The 354V from Mullard is a detector and general purpose audio valve. The design originally operated with a maximum anode voltage of 200 and was improved in 1930 and again in 1935 with the final design having a 250 Volt maximum anode rating. The mutual conductance also increased over the development cycles from 2.4 to 3.4 mA/V.
The original 354V triode dates from 1929 and in 1935 the heater current requirement was reduced to 0.65 Amp. This example has a 0.65 Amp heater and thus can be dated to the mid 1930s or later.
The mesh anode with the control grid visible within. Note also the cathode tube that is closed at the top and has a reduced diameter for the section held by the top mica.
The mica holding the electrodes in the shoulder of the envelope flexes to grip the glass.
Top view showing the shape of the holding mica.
The classic envelope is 42 mm in diameter and, excluding the B5 base pins, is 90 mm tall.
References: Data-sheet & 1043 Type 354V was first introduced in 1929. See also1929 adverts.
