GB1100151A - Improvements relating to dynamic convergence circuits for a multiple gun cathode ray tube - Google Patents

Abstract

1,100,151. Cathode-ray tube circuits. ELECTRIC & MUSICAL INDUSTRIES Ltd. 8 Sept., 1964 [14 Sept., 1963], No. 36271/63. Heading H4T. Relates to arrangements for electromagnetic dynamic convergence in a three-gun cathode-ray tube (C.T.R.) for displaying coloured images. According to the present invention waveforms linearly and non-linearly related to the normal deflection are applied to electro-magnets in proportions determined, for a given deflexion direction, by a single control means. In the embodiments the non-linear waveform is parabolic and the O.R.T. a " shadow-mask " tube. In one embodiment for each scanning direction the sawtooth and parabolic waveforms are combined after amplitude adjustment of the latter and the combined signal is fed to the " red ", " green ", and " blue " electromagnet coils after separate amplitude adjustment, Fig. 1 (Prov., not shown). In a modification separate combining circuits corresponding to the three colours are utilized, Fig. 2 (Prov., not shown). In a further embodiment the same outputs are provided for convergence correction of the "red" and "green" beams: a sawtooth voltage at line frequency is applied to an inverting amplifier 111 which is bridged by a potentiometer 113 and integrator 116 produces a parabolic voltage. The combined waveform is applied at adjustable level (potentiometer 118) to a clamping circuit associated with an amplifier 131; similarly, amplifier 132 corresponds to frame deflexion, and the outputs of the amplifiers are fed in common to the " red " and " green " electromagnet. Further potentiometers 137, 138 are associated with the " blue " electromagnet. The adjustment procedure is given.