| 摘要 |
1,257,712. Cathode-ray tube circuits. R.C.A. CORPORATION. 7 March, 1969 [11 March, 1968], No. 12150/69. Heading H4T. In a convergence circuit for a multi-beam cathode-ray tube, two convergence windings, specifically the windings 1H and 2H (Fig. 1) for horizontal convergence correction of the red and green guns of a tri-gun colour display tube, are connected in series and supplied via an adjustable inductor 13 with pulses of horizontal frequency from the horizontal deflection circuit. The inductor 13 integrates the pulses and provides a sawtooth voltage which is integrated by the convergence windings to produce therein a parabolic current wave, the amplitude of which may be adjusted by adjustment of the inductor 13. During the first half of the horizontal scan period diode 18 conducts and the rectified current flowing in the windings 1H and 2H clamps the trough of the parabolic current to a fixed valve, so that static centre convergence does not change as a function of control adjustments. During the latter half of the horizontal scan, when diode 18 is non- conducting, the shunt path including resistor 17 and diode 18 has a high resistance and the amplitude of the saw-tooth may be adjusted by adjustment of potentiometer 16 in the shunt path including capacitor 14 and resistors 15 and 16 without such adjustment affecting the conditions during the first half of the scan during which adjustment is effected by means of the inductor 13. This latter adjustment, which is made first, a cross-hatch generator producing a pattern of equally spaced vertical and horizontal lines being employed, aligns the vertical red and green lines on the lefthand side of the screen (the first half of the horizontal scan) after which potentiometer 16 (the master tilt control) is adjusted to align the vertical red and green lines on the righthand side of the screen (the last half of the horizontal scan) and differential tilt control is then affected by means of potentiometer 20 to align the horizontal red and green lines. The blue horizontal convergence circuit is a known type. Component values are given. |
