Scanning and E.H.T. circuits for wide-angle picture tubes

One of the major factors which have contributed to the low cost of television receivers, despite the increased cost of production, is the introduction of a.c./d.c. technique. In this country this implies the rather low H.T. rail potential of about 190 V. The demand for bigger and brighter pictures, on the other hand, has led to an increase in the scanning angle of some C.R. tubes, and of the final anode potential. Both these factors imply greater scanning power. The paper is concerned with combined scanning and E.H.T. circuits developed to meet this situation. The operation of energy-recovery scanning circuits is explained, design procedures established and typical circuits are given in detail. Particular attention is paid to the problem of obtaining satisfactory linearity, and a method is described of correcting the horizontal nonlinearity by means of a saturated reactor. Details are also given of an efficient scanning coil wound on a slotted ferrite yoke.