The Type 45 directly heated audio output triode was designed by Westinghouse in 1928 and was originally designated the UX245. This exhibit is the earlier style housed in a balloon envelope.
The blackened box anode has moulded ridges across the broad face. This corrugation adds rigidity without adding weight.
The detail picture shows the pinch, anode, control grid wire and twin inverted V filament complete with fine tensioning springs.
The production of the 45 ended in around 1932 but has recently been put back in production as it has a well deserved reputation for good audio fidelity.
Many thanks to Simon Balderson for donating these images and valve details.
The balloon envelope is 54 mm in diameter, and excluding the UX4 base pins is 113 mm tall.
References: Data-sheet & 3002. Type 45 was first introduced in 1929. See also1929 adverts.
