The S4VA is a pentode, unfortunately we could only locate details for the MS4B equivalent.

A striking feature of this valve is the small anode plates sited either side of a substantial grid cage.

The vertical wires in the foreground connect to the anode. As can be clearly seen the grid cage has three sets of supports for the three grids, the outer being the screen grid.

In the picture above the separation of the anode plate, left, from the grid cage can be seen.

The S4VA and S4VB specimens are typical of earlier Mullard oxide-process AC mains types (early to mid 1930s). The unsprayed S4VA has a less sophisticated form of assembly than the S23 and still relies on hand assembly using glass bead insulators. The internal skirt connected to the screen grid is a prominent feature of the design. The red-gold colour of the sprayed S4VB, and its unsprung base pins, show that it is relatively early for its type. By the later 1930s Mullard was buying MOV MS4Bs, spraying them with gold paint, and relabelling them as Mullard S4VAs.

The classic envelope is 46 mm in diameter and, excluding the B5 base pins, is 124 mm tall.

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	4.0	1.0	200	80	-1	3.4	1.2	0.35M	3.2

This exhibit was last updated on 07 February 2003