The EE50 dates from 1938 and was a product of the quest for RF valves for television. Television was not only transmitted at high frequencies but also had a wide bandwidth. To provide gain under these conditions required a high mutual conductance from the valve. Traditional valve making practice would not produce a suitable device.
Manufacturers tried different techniques to overcome the problem with electron multiplication being one option. The EE50 can also be regarded as a secondary emission pentode. The second cathode would be maintained at about 150 Volts positive of the main cathode. This cathode would operate at about 8 mA of current and circuits of the time show the output being taken from this second cathode.
The EE50 can also be seen as a dead end, as within a few months Philips had developed the conventional valve to give similar performance but with lower noise. This second landmark was the EF50 that became so important in WWII as Radar reception needed the same characteristics of wide bandwidth and high frequency as Television. In fact the PYE 45 MHz IF strip was developed for TV and used extensively for Radar.
This early version of the EE50 has base pins that turn to the horizontal after a few mm. The spigot has a locating keyway and so the base was not of the bayonet type. The valve must have pushed into horizontal clips.The word on the painted glass is ?rygave. Later versions with B9G base pins also were enclosed in an aluminium can the same as the EF50.
The lettering on the base skirt is SN3 with an E in a square box.
The base pins. The aluminium skirt is clamped over the glass rib where the hard glass glass foot joins to the soft glass envelope.
The folded pins. The early hard metal pins did not deform but passed breaking stresses to the glass seal. later developments on other valves used softer metal with pointed ends and a small waist at the glass seal to allow slight bending without breaking the vacuum seal.
Another view of the base.
The wide glass tube envelope is 32 mm in diameter and, excluding the B9G base pins, is 55 mm tall.
References: Data-sheet. Type EE50 was first introduced in 1938. See also1938 adverts.
