This 5AQ4 from the English factory of Tungsram is a full wave rectifier with a maximum rectified output of 175 mA. The minimum series resistance to prevent excessive current flow is 100 Ω.
The cathode is tubular and each anode has an X cross section.
Face view of one anode showing how the thin plate is stitched together. The other arms are shorter.
A closer view. The heater is a single inverted V in each cathode.
The classic envelope is 44 mm in diameter and, excluding the IO base pins, is 101 mm tall.
References: Data-sheet, 1040 & 1043. Type 5AQ4 was first introduced in 1949. See also1949 adverts.
