The PM2A is an early audio output valve. It is designed for battery operation and, naturally, the output power is very low. The anode load is quoted as optimum at 7,000 Ω.
The base pins are split and opened to grip the socket. Above the pince the anode can be seen to be mounted horizontally. The black inner to the envelope is a result of the mechanism of the Azide process to form an oxide emitting surface.
The The dome carries the identification.The balloon envelope is 45 mm in diameter and, excluding the B4 base pins, is 88 mm tall.References: 1931 data-sheet & 1043. Type PM2A was first introduced in 1930. See also 1930 adverts. |
