The S4V screen grid valve was introduced in 1929. The literature says it has a B5 base but this is an S4V on a B4 base. It is indirectly heated but there seems to be no connection to the cathode. One can speculate that the cathode connects to the mid point of the heater at the top.
The envelope etching has the Mullard name and clearly S4 the V can not be seen. Below the Type designation is an aerial symbol - originally from the ORA valve.
The other side of the envelope carries the Mullard logo.
The screen grid is formed as a screening box with close spaced wires. The control grid can be seen at the centre with the cathode tube and insulated heater. Note the absence of connection to the cathode tube.
Through the silvered envelope one can make out the screen grid cage and the small flat plate of one half of the anode. The other side of the screen also has a plate for the anode.
This came with a label stuck-on claiming it was a CV1324. Close examination indicated it was an S4V both from the original label and the etching on the envelope.
The balloon envelope is 44 mm in diameter and, excluding the B4 base pins, is 98 mm tall.
References: Data-sheet & 1043. Type S4V was first introduced in 1929. See also1929 adverts.
