The N43 is an output pentode suitable for both audio and video use. The load impedance required is 5,400Ω. The cathode resistance is 90Ω and in single ended configuration the output is 4.5 Watts.
The M-OV lozenge with the N43 within. The paper label with the Marconi brand can be seen at the top. This image has been laterally reversed as the N43 is being seen through the back of the glass.
The substantial box anode with side supports holding the mica supports.
The control grid is wound on copper supports that are topped by a substantial heat radiating fin.
The box anode sits in the middle with screening trays attached to both micas.
The classic envelope is 57 mm in diameter, and excluding the B7 base pins is 138 mm tall.
References: Data-sheet & 1040. Type N43 was first introduced in 1936. See also1936 adverts.
