The PenA4 is an audio pentode power output valve.
For the heater power the emission is not high and the audio output achieved is small. It is specified for single ended use, as would be found in radio receivers.
The top mica area. The copper supports for the control grid are topped with a heat radiating fin.
The classic envelope is 49 mm in diameter and, excluding the B7 base pins, is 120 mm tall.
References: Data-sheet, Data, private correspondence & 1043 Type PenA4 was first introduced in 1937. See also 1937 adverts.
Absolute Maximum Operating Conditions¶
Updated January 19, 2023.