GB1249798A - Color television picture tube - Google Patents

Abstract

1,249,798. Colour television tubes. SONY CORP. 10 Feb., 1970 [20 Feb., 1969], No. 6437/70. Heading H1D. [Also in Divisions H3-H5] In a colour television tube of the shadow mask type, misregistration due to thermal expansion of the shadow mask or grid is prevented by providing an auxiliary deflection coil behind the main deflection coil and energised in opposition to it to a variable extent by means including an inductance having a core the permeability of which reduces as its temperature increases; this core is mounted on the neck or the cone of the envelope so that as the shadow mask heats up the cone also heats up thereby effectively moving the centre of deflection to compensate for the expansion of the mask. In one arrangement, Fig. 3 (not shown), the inductance is in parallel with the auxiliary coil and both are in series with the main deflection coil so that the current through the auxiliary coil reduces with increasing temperature of the tube. In another arrangement, Fig. 6 (not shown), the main coil is in series with the primary winding of a transformer with a core whose permeability decreases with increasing temperature, and the secondary winding of the transformer feeds the auxiliary coil. In a modification of this arrangement, Fig. 7 (not shown), the auxiliary coil is also energised from an adjustable D.C. supply for centring the beams, an inductance and a capacitor being included to isolate the D.C. supply, and the transformer secondary winding from each other. If the shadow mask is in the form of a grid with vertical apertures it is necessary to compensate only the horizontal deflection.