Line flyback pulse signal for TV receiver - is generated using separate winding on picture width setting choke

摘要

Impulses (14) in synchronism with the line reset signals applied to the line deflector coils (8) are derived from a second winding (12) on the variable choke (10) in the picture width control circuit. By obtaining the impulses in this manner a second winding on the line transformer is avoided. The transformer can be designed specifically for its main duty. Any increase in leakage flux due to added windings is avoided, and distorting harmonics eliminated. In addition to its use as a synchronising signal for the line scan, the reset impulse can also be applied to a fault detection system. If the pulse amplitude departs from normal, ie if it becomes too high signifying an excessive current due to high power supply voltage (+U1), the protective circuit.