The 230HPT output pentode from Cossor dates from 1931, and was designed for battery operation. The 230HPT had a short time as a valve of choice and was obsolete by 1932.
The side contact connected to the screen grid and when the valves was issed with a B5 base cap, from 1933, the screen grid connected to pin 5.
The anode is a two part box section of bright nickel. The embossed lines and C add rigidity to the thin metal. The side contact is an insulated screw cap.
The top of the dome carries the etched identification and BVA logo. The filament is held under tension by the springs seen on the top mica. The wire grids can clearly be seen.
This image shows the relative spacing of the grids and their pitch. The four strands of oxide coated filament are also clearly visible.
This picture shows the open centred moulding used by Cossor for their bases. The pins are of one part construction with the wires soldered to the lower part of the pin.
The balloon envelope is 50 mm in diameter and, excluding the B4 base pins, is 104 mm tall.
Reference: 1043. Type 230HPT was first introduced in 1931. See also1931 adverts.
