The N37 is a television type audio output pentode.
The load impedance is 6000 Ohms and the cathode resistor is 330 Ohms. At 10% total harmonic distortion the valve can produce 2.3 watts of audio.
The red Marconi label covers most of the envelope circumference.
The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 58 mm tall.
References: Datasheet & 1040.
Absolute Maximum Operating Conditions¶
Updated May 03, 2013. shape:thin.glass.tube construction:all.glass type:pentode age:1950.1960 base:b7g heater:300ma pins:7 pin:1.g1 pin:2.k pin:3.h pin:4.h pin:5.a pin:6.ic pin:7.g2