CRT Overshoot Compensation Circuit
Original Publication Date: 1988-Sep-01
Included in the Prior Art Database: 2005-Feb-15
This article describes a circuit which compensates the CRT Overshoot by using the charge up time R-C log network applied to the control grid (G1) bias circuit portion. After the application of the power to the CRT gun, the beam current will rise sharply and saturates when the heater is fully warmed up. The distance of Cathode-G1 increases for a few minutes due to a thermal expansion of a metal grids, and the beam current decreases gradually until the thermal expansion reaches the stable state after the overshoot point which exceeds the saturation level. This is so called CRT Overshoot. As a result, bright background rasters will appear for a few minutes after power on. The figure shows a diagram of the overshoot compensation circuit.