COLOR CATHODE RAY TUBE DEFLECTION YOKE ADJUSTMENT

A process for making the axial adjustment of the deflection yoke on a color cathode ray tube display assembly of the shadow mask variety. Before this adjustment is attempted, the color purity adjustment must first be made. This involves disabling two of the three electron guns and then, by known manipulation of the "color purity magnets" causing the beam landings to coincide with the correct phosphor dots in the center of the tube. The deflection yoke is then adjusted while normal operating potentials are applied to the tube, except for the disabled guns, normal deflection signals are supplied to the yoke, and an axial magnetic field is applied at the tube faceplate. The axial field is made strong enough to shift non axial electron beams to the adjacent phosphor dots thereby creating a color display pattern having radial components of a color corresponding to that of one or more of the two disabled electron guns. When the deflection yoke is correctly positioned, the radial pattern components will be symmetrical and will have straight lines. Incorrect adjustment will result in skewed or curved components. The yoke is moved to achieve a pattern having the highest degree of symmetry and straight edges.