Sensibly equivalent¶ to:
The 4212E large directly heated transmitting triode is a magnificent specimen. It was made in the UK by STC as the 4212E but the design originated with Western Electric in America as the famous type 212. The 4212E replaced the 4212D in the late 1930's.
The original Type 212 was a classic landmark valve designed as a powerful audio amplifier for professional use as a modulator in medium-sized broadcast transmitters (very numerous in the US). Subsequent versions, culminating in the 4212E, progressively raised the ratings until a push-pull pair in Class AB could deliver approximately a kilowatt of audio modulation power. Once widely used in local radio stations, and other professional applications, the type was still in quantity production during the 1970s (fifty years!) and may still be available.
The American originals all had thoriated tungsten filaments but some of the later copies, including, we think, the MZ2-200, had somewhat more economical oxide-coated filaments.
Professionals preferred the originals every time!
A transmitter at HMS Collingwood uses four of these valves in the PA.
The short fat pins and base pip indicate a bayonet fitting base. This type of base has spring contacts that the pins slide into.
This photograph of a perfect condition 4212E was sent in by Paul Young.
The wide glass tube envelope is 85 mm in diameter and, excluding the base pins, is 297 mm tall.
References: Private communication, datasheet & 1043.
Absolute Maximum Operating Conditions¶
Updated February 20, 2017.