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Ed Reitan's Color Television History

Color Line

RCA Laboratories Developmental Color Receivers

2nd Triniscope

The Last in the Series of the RCA Labs / Camden Trinoscope Color Receivers

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During the FCC hearings on Color Television in 1949 and 1950, a number of experimental receiver/monitors for the presentation of the RCA Dot-Sequential Color Television System were demonstrated to the commission. More than 15 different models have been identified (and will be described in future updates). All of these units were engineered by Ray Kell and his group at RCA Laboratories. Dalton Prichard headed receiver design.

Most of these receivers were of the Triniscope type, with three separate red, green, and blue CRT's with optically combined images. The series culminated with the single gun and triple gun shadow mask color CRT receivers demonstrated to the FCC in March, 1950.

Color Line

RCA Trinoscope Color Receiver (1950)

The last Trinoscope model was started in development in March, 1950 and a quantity of ten was completed by May. For design of this receiver, the Labs cooperated with the Color Products Development Group of RCA Victor at Camden. The model employed three 10-inch metal kinescopes (70 degree deflection angle), a total of 44 tubes, and four separate chassis units. It was housed in a cabinet 40-inches high, 37 1/2-inches wide and 21-inches deep. This is the last of the series of trinoscopes. RCA unveiled its 16-inch metal cone shadow mask color kinescope to the FCC and the press on March 29, 1950. After that time, all RCA work concentrated on the development of shadow mask receivers by the Camden Group.

The optical arrangement, shown in the photo. consists of the red, blue, and green kinescopes, two dichroic mirrors and a front silvered plane mirror in the lid. The first dichroic is oriented at a 45-degree angle between the vertical green CRT at the bottom of the cabinet and the horizontal blue CRT at the optical assembly's center. This mirror reflects blue light upwards and passes green light from the lower CRT. Above and parallel to the first mirror is a second dichroic which reflects light from the upper horizontal red CRT and passes the green and blue light for viewing on a plane mirror in the hinged cabinet lid. While phosphors of the blue and green tube were sufficient for good chromaticity, no suitable red phosphor was available at that time. Therefore a red Wratten filter was placed over a yellow phosphor CRT, and neutral density filters were used to balance light output.

No schematic for this set has been located but the four chassis units appear to be:

  • Receiver / Sampler
  • Horizontal/Vertical Deflection
  • Low Voltage Power Supply, and
  • RF High Voltage Supply for the three CRTs

It is assumed that high level sampling was used whereby wide band video was applied directly to all kinescope grids, and sampling gating pulses were dot sequentially applied to each kinescope cathode.

2nd Triniscope

One of the two known surviving Trinoscope receivers, shown above, was donated by RCA Laboratories in Princeton, N.J. to the UCLA Film and Television Archives.

To be continued...... (with a detailed description of all models)

Color Line

V1.01 1/18/97

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