PROCESS FOR THE AUTOMATIC GENERATION AND CORRECTION OF THE CUT-OFF VOLTAGE OF AN ELECTRON GUN AND APPARATUS FOR CARRYING OUT THIS PROCESS

摘要

The blocking voltage of an electron gun is corrected by periodically removing an input video signal and driving a cathode with a DC stabilizing voltage. A pulse perturbation is impressed upon a control grid and the cathode momentarily conducts more heavily to exceed a predetermined threshold corresponding to the limit of a black CRT picture. A feedback loop detects a response signal from the perturbation of cathode current and stores the response signal in a memory, the latter determining the corrected blocking voltage during normal operation of the gun.