An Improved Convergence System for In-Line Gun Color Picture Tubes

Convergence of the three color beams in an in-line gun cathode ray tube is a relatively easy task. The three unconverged rasters are parallel and differ only in size. Convergence of the electron beams of the two outermost guns upon the electron beam of the center gun is accomplished by adjusting the amplitude of a sawtooth current, which can be used because the convergence errors at the North and South and at the East and West areas of the screen are equal and in opposite directions. Since amplitude rather than wave-shaping controls are used, the number of dynamic controls can be significantly reduced from the thirteen used in the conventional delta gun system. Each of the two outermost electron guns has only two static and two dynamic convergence adjustments. The dynamic controls use the horizontal rate deflection yoke current to converge the vertical lines and the vertical rate deflection yoke current to converge the horizontal lines. A prototype assembly is shown in Fig. 1. The improved system designed by Sylvania now makes it possible to achieve convergence that is equal to the convergence obtained with the delta gun system.