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Cathode Ray Tubes

& Electon Guns

Cathode Ray Tube displays dominated electronic for over 100 years but have now become mostly obsolite. They are still amazing examples of engineering and applied physics with facinating history and theory of operation. Two miniture monochrome CRTs used in camcorders shown in the image.

Early monochrome commercial TV set from the 1950s often used simple electron guns with external magnetic focusing. They also used 'ion-traps' to prevent screen damage. Aluminium coating backing the fluorecent screen removed the need for 'ion-traps'. Electrostatic focus added to the gun removed the need for large magnet assemblies on the tube neck. Gun development for B&W CRTs can be seen from the link.

Colour CRT The image is of a Sony Trinitron tube. Until these tubes were available earlier colour tubes used 'delta' guns and 'shadow-masks' The shadow-mask blocked a large area of the screen from beam landing. The Trinitron addressed this with its 'Aperture-Grille' The image link explains more.

War-time Tubes Radar was developed during WWII. The tubes used for radar and oscilloscopes use electrostatic diffelection may of these founf themselves being used in DIY televion after the war. This example is probaly manufactured by Cosor. The electron gun shown in the banner to this page is of the same type.

Oscilloscope tubes Similar in construction to the tube above this example is from a Tektronix analogue storage scope. A techneque using screan coating and flood guns allowed a trace to be maintained on the phosphor screen after it was writen by the beam. These remaind until digital storage techneques oftered a cheaper alternative method of storage.

Educational CRTs The CRT being a big part of electronics and particle beams being physics an number of manufacturers provided different CRTs for demonstration in schools and colleges. They have unfortunately fallen out of favour with schools.

Images link to more information on the construction detail of each type of CRT.

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