GB610081A - Improvements in deflecting coil circuits - Google Patents

Abstract

610,081. SAW-tooth amplifying circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Feb. 2, 1946, No. 3364. Convention date, May 30, 1942. [Class 40 (vi)] In a circuit for deflecting a cathode-ray beam, comprising a pair of series-connected deflecting coils, the non-uniform distribution of capacity across the coils which causes them to resonate at a number of different frequencies is rendered substantially ineffective. As shown in Fig. 1, a diode 40 is used to suppress the parasitic oscillations due to the coil 25 resonating with the non-uniform distributive capacity 32, the lower frequency parasitic oscillations due to the coils 24, 25 in series resonating with the distributive capacity 30 are suppressed by the diode 34 as described in Specification 566,835. Resistance 42 limits the diode current flowing in coil 25 at the start of each deflection cycle. In a modification, Fig. 2 (not shown), a tightlycoupled choke coil is connected in parallel with the deflecting coils having corresponding points of the choke coil and deflecting coils connected so that the reactances ratios between such points are maintained equal. By this means all sections of the deflecting coils are effectively inductively coupled, thus reducing the effect of the non-uniform distribution of inductance and capacity in the deflecting coils. Alternatively, the distributed capacity 32 across coil 25 may be balanced out by using an auxiliary capacity across coil 24, Fig. 3 (not shown), this capacity being adjusted until the scanning defects are reduced to a minimum.