Sensibly equivalent¶ to:
The PM1HL is an amplifier triode with external gold metallising paint and a 2.0 Volt filament.
The electrodes are obscured by the coating on the envelope. The PM1HL was designed as a detector and general purpose valve. It was intended to be used in domestic broadcast receivers.
The balloon envelope is 40 mm in diameter, and excluding the B4 base pins, is 80 mm tall.
References: 1931 data-sheet & 1043. Type PM1HL was first introduced in 1931.
Absolute Maximum Operating Conditions¶
Thanks to Andy Cowley for supplying the above PDF datasheet.
Updated September 11, 2021.