Automatic kinescope bias control system compensated for sense point impedance variations

摘要

In an automatic kinescope bias (AKB) control system, a signal with a magnitude representative of the black current level conducted by the kinescope of a television receiver is derived from a sense point. The derived signal is coupled via a signal path to a processing network including input clamping and sampling networks for developing a bias correction voltage. A source of auxiliary control signal, coupled to the signal path prior to the clamping network, is subject to being undesirably influenced by impedance variations manifested by the sense point. An impedance included in the signal path between the sense point and the auxiliary signal source compensates for the sense point impedance variations, and also increases the immunity of the clamping network to spurious signals including noise and locally generated interference.