Sensibly equivalent¶ to:
The S4VB is a tetrode. For internal details refer to type S4VB.
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 show that it is relatively early for its type. By the later 1930s Mullard was buying M-OV MS4Bs, spraying them with gold paint, and relabelling them as Mullard S4VAs.
The balloon envelope is 49 mm in diameter and, excluding the B5 base pins, is 118 mm tall.
The top of the envelope shows the large circle of adhesive where the screw type top cap was once located.
References: 1931 data-sheet, private communication & 1043. Type S4VB was first introduced in 1930. See also 1930 adverts.
Absolute Maximum Operating Conditions¶
Thanks to Andy Cowley for supplying the above PDF datasheet.
Updated February 05, 2022.