Failure compensated automatic kinescope beam current limiter

Abstract

An automatic kinescope beam current limiter for a television receiver includes a source of derived beam current representative voltage, a keyed sampling circuit for developing an output beam current control voltage on a charge storage capacitor in response to the derived voltage, and an auxiliary current path including an impedance coupled between the output capacitor and the source of derived voltage. In a normal beam limiting control mode, the control voltage from the sampling circuit serves to modify the television signal in response to the derived voltage in a direction to limit excessive beam current. In an abnormal control mode such as when the sampling circuit is inoperative due to disrupted keying, current is conducted via the auxiliary current path in response to the derived voltage to modify the control voltage on the capacitor with a sense and at a rate for limiting excessive beam current, to thereby preserve beam limiting capability.