GB1373524A - Toroidal deflection yoke having asymmetrical windings - Google Patents

Abstract

1373524 Electron beam deflecting apparatus RCA CORPORATION 26 Nov 1971 [7 Dec 1970] 55000/71 Heading H1D A toroidal deflection yoke for a delta gun, e.g. shadow mask colour TV tube comprises vertical and horizontal coil winding portions in each of four quadrants defined by vertical and horizontal axes, wherein for minimizing unsymmetrical convergence of a displayed raster in a direction along at least one of the deflection axes, the conductor distribution of at least the vertical or horizontal coil winding portion in a first quadrant is selected to be asymmetrical relative to the winding distribution of the correponding (i.e. vertical or horizontal) coil winding portion in a second quadrant adjacent the first quadrant, the first and second quadrant lying on the same side of a deflection axis along which said unsymmetrical convergence would appear. Corrections may be for misconvergence caused by asymmetry of gun assembly, interaction of getter structure and field, imbalances due to vertical component of earths field. Fig. 2 (not shown) illustrates asymmetric top to bottom misconvergence for a symmetrical yoke, Fig. 3 (not shown), indicating left to right misconvergence with left shifted blue line (32) created by getter structure and field interaction. Left to right misconvergence for example may be corrected by asymmetry in the two lower quadrants, and optionally a slight asymmetry in the upper two quadrants. Other correction combinations are discussed. The Fig. 4 winding compensates for the Fig. 2 and 3 aberrations with first and second winding layers 41, 42, which may alternatively be interspersed in a single layer. Layer 41 is symmetrical and interconnected with layer 42 as in Fig. 5 (not shown). Quadrants I, IV are asymmetric for correction of the Fig. 2 aberration, in the horizontal conductors, although vertical conductors could be asymmetrically altered, as well or instead. For correction of the Fig. 3 aberration the horizontal conductors in quadrants III and IV (layer 42) are asymmetric. Either or both vertical and horizontal windings may be asymmetric. The horizontal coil windings may be series or parallel connected, the vertical windings being normally series connected. Dynamic corner correction waveform circuitry is not required. Fig. 1 (not shown) includes getter structure (18) mounted adjacent the gun assembly along the envelope surface, terminating in structure (19) ahead of the yoke. Yoke conductors are wound about rings (23), (24) on ferrite core (22). Wide angle tubes are mentioned.