Color cathode ray tube deflection yoke evaluation

Claim 1

A process for evaluating the coincidence of deflection centers of the horizontal and vertical deflection coils of a magnetic deflection yoke for use with a shadowmask color cathode ray tube; said process being carried out on an operating shadowmask cathode ray tube display including a shadowmask cathode ray tube having a neck portion and a bell portion, a power supply for producing the currents and potentials to operate said tube, horizontal and vertical deflection current supply sources, and an externally mounted adjustable color purity magnet assembly; said process comprising: a. mounting the yoke to be tested in approximate position on said neck portion of said tube, b. connecting said yoke to said deflection current supply source, c. operating said tube so that only one of the three electron guns in said tube is functional, d. establishing a magnetic field having an axial direction in said bell portion of said tube, e. adjusting the magnitude of said field to produce a color pattern having a central bullseye surrounded by six, generally wedge-shaped alternating color regions, f. adjusting said purity magnet assembly on said tube to produce a bullseye color corresponding to the desired color for the energized electron gun and to center said bullseye on the screen of said tube, g. rotating said yoke around the axis of said tube while maintaining a fixed axial position to produce at least a 90* rotation, and h. observing the motion of said color pattern and the motion of the juncture between said alternating color regions as said yoke is rotated, said motion being indicative of the degree of lack of coincidence between said horizontal and vertical deflection centers.