The RCA SB256 Selectron

The 256-bit production Selectron



Image of the SB256 Selectron
For high resolution images of the SB256, and other devices, please visit http://lampes-et-tubes.info/

The SB256 is organized as a 2 by 128-bit memory.


Image of the complex base and wiring, 
including two coaxial connector pins sealed throught the glass Photo Courtesy of Giorgio Basile http://lampes-et-tubes.info/

The two bit-output lines (the signal electrodes originating within the Faraday cage) are coaxially shielded pins passing through the tube base (above) and mating with a custom socket (below) manufactured by Alden Products Company. The coax sockets required a pin recepticle itself floating within the floating shield recepticle. This was required to minimize stress on the glass base from alignment errors in the manufacture of both tube and socket.

Image of black phenolic socket for the SB256

Image of advertisement for the SB256 socket Image of advertisement for the SB256 socket

Advertisement from the March 1951 issue of Electronics Magazine, Copyright McGraw-Hill