The nuvistor is a type of vacuum tube announced by RCA in 1959. Nuvistors were made to compete with the then-new bipolar junction transistors, and were much smaller than conventional tubes of the day, almost approaching the compactness of early discrete transistor casings. Due to their small size, there was no space to include a vacuum fitting to evacuate the tube; instead, nuvistors were assembled and processed in a vacuum chamber with simple robotic devices. The tube is made entirely of metal with a ceramic base. Triodes and a few tetrodes were made; Nuvistor tetrodes were taller than their triode counterparts. Nuvistors are among the highest performing small signal receiving tubes. They feature excellent VHF and UHF performance plus low noise figures, and were widely used throughout the 1960s in television sets (beginning with RCA's "New Vista" line of color sets in 1961 with the CTC-11 chassis), radio and high-fidelity equipment primarily in RF sections, and oscilloscopes. RCA discontinued their use in television tuners for its product line in late 1971. Other nuvistor applications included the Ampex MR-70, a studio tape recorder whose entire electronics section was based on nuvistors, as well as studio-grade microphones from that era, such as the AKG/Norelco C12a, which employed the 7586. It was also later found that, with minor circuit modification, the nuvistor made a sufficient replacement for the obsolete Telefunken VF14 tube, used in the Neumann U47 studio microphone. Tektronix also used nuvistors in several of its high end oscilloscopes of the 1960s, before replacing them later with JFET transistors. Nuvistors were used in the Ranger space program and in the MiG-25 fighter jet, presumably to harden the fighter's avionics against radiation. (See radiation hardening.) This was discovered following the Defection of Viktor Belenko.

Pin layouts

The Nuvistor sockets have a standardized layout based on four (imaginary) concentric circles with the pins laid out at 60 degree angles from the center point of the base. The metal shell has two fins that extend below the base; the larger of these two fins is the key position. (NOTE: Nuvistor sockets have a potential of up to 12 pins, but usually have only five or six pins.) Pins 1, 2 and 3 are assigned to the outermost circle, with Pin 1 located 60 degrees clockwise of the key fin. Pin 2, which is in line with the small fin, is 120 degrees clockwise of Pin 1. Pin 3 is 120 degrees clockwise of pin 2. For triodes, these pins (usually just Pin 2) are the plate/anode connection. For tetrodes, one of these pins is the screen grid connection and the plate/anode has a top cap connection. Pins 4, 5 and 6 are assigned to the next circle. Pin 4 is in line with the key fin. Pin 5 is 120 degrees clockwise of Pin 4 and the key fin. Pin 6 is 120 degrees clockwise of Pin 5. The pins in this circle (usually pin 4) connect to the control grid. Pins 7, 8 and 9 are assigned to the next circle. They are in the same lines as Pins 1, 2 and 3 and also increase in order going clockwise. These pins (usually pin 8) connect to the cathode. Pins 10, 11 and 12 are assigned to the innermost circle. They are in the same lines as Pins 4, 5 and 6 and also increase in order going clockwise. These pins (usually Pins 10 and 12) connect to the heater. Base 12AQ -- which is used by most triodes, including 6CW4 and 6DS4 -- is the most common connection layout. The connections are: Base 12AS is the tetrode layout. The connections are:

Types

Dissection of a Nuvistor triode tube