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The WD142 is a variable μ pentode and a single diode package. The Mullard UAF42 is its equivalent. This type of valve was designed for radio receivers. The variable μ characteristic enables the gain to be varied according to signal strength via an AGC circuit. This valve could have been used for AGC detection and as final IF amplifier.

Initially B8A valves had metal skirts with locating pip and spigot, then the metal skirt remained with just the locating pip and finally the glass had a moulded skirt and locating pip.

The outer screen obscures most of the inner structure.

The thin glass tube envelope is 20 mm in diameter and, excluding the B8A base pins, is 52 mm tall.

References: Data-sheet & ¹⁰⁴⁰. Type WD142 was first introduced in 1948. See also 1948 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.