The Nuvistor
This type of valve is intermediate between valves of normal construction and disc-seal or stacked ceramic. The electrodes are of cylindrical shape but smaller than those generally employed and are rigidly supported from one end by a tripod-like structure on a ceramic base.
The supports are continuations of the pins which are sealed through the base. No use is made of mica or glass supports or spacers. This construction produces rugged and efficient valves having low leakage and low microphony. Because the structure is so small the capacitance between electrodes and the lead inductance is low, resulting in a good performance and low noise at VHF.
By the late 1950s the transistor had clearly shown that it was capable of replacing valves in many applications. RCA developed the Nuvistor as one of the last major advances in valve technology and its size at little more than the size of a typical transistor of the day was deliberate. The first Nuvistor was developed in 1959. All Nuvistors had 6.3 Volt heaters, a special base and low inter-electrode capacitance. The majority were triodes but a few were tetrodes.
Their main use was in receiver front-ends, where they provided good performance coupled with low noise up into the VHF and UHF frequency ranges. Both television and radio receivers used the Nuvistor. As well as receiver use the Nuvistor was extensively used in high quality test equipment such as oscilloscopes. In this application they could be found as the first stage in the vertical or Y amplifiers.
Typical devices are: 7586 The first one released, a medium μ triode. 7587 A sharp cut-off tetrode. 7895 As 7586 but with higher μ. 8056 A triode for low anode voltages. 8058 A triode with anode cap & grid on shell designed for UHF performance. 6CW4 A high μ triode often used in television receivers of the early to mid 1960s period. 6DS4 A remote cut-off variant of the 6CW4. 6DV4 A medium μ triode designed as UHF oscillator. In some production runs the case of the 6DV4 was gold plated.