Sensibly equivalent¶ to:
The Pen4VA was, eventually, the Mullard answer to the landmark Mazda AC/Pen of 1930 for audio output within AC mains sets. The photo shows a post-war specimen made for replacement purposes. Following a series of rather less successful attempts to make indirectly-heated output pentodes (Pen20) the successful but obsolescent Pen4BA was introduced with a B7 base cap (by then, after 1933, current) but Pen4VA B5 versions were supplied as replacements for its less successful predecessor the Type Pen4V. These were designated Pen4VA (5).
The original valve took 12 mA of screen current. The revised version of 1937 reduced this to 3.0 mA and with a cathode resistor of 500 Ω and a 6 kΩ load produced 3.8 Watts as opposed to the original 3.4 Watts.
The image shows a mesh anode with wire grids and oxide coated cathode. The construction uses a glass rod for support whereas later designs will adopt the classic (or shouldered) envelope and mica supports.
Thanks to Peter Lawn for the image and Mike Edwards for the equivalents data.
The balloon envelope is mm in diameter, and excluding the B7 base pins, is mm tall.
References: Private communication, 1043 & 4024. Type Pen4VA was first introduced in 1933.
Absolute Maximum Operating Conditions¶
PDF scanned from an original document held by the museum
Updated February 23, 2017.