Kinescope bias arrangement to provide both constant amplitude dc restoration pulses and arc discharge protection

Claim 1

In a color television receiver including a color kinescope of the type employing a plurality of electron guns, each one of which has a grid and cathode electrode for controlling the intensity of a beam produced by said gun in accordance with the potential difference between said grid and cathode electrodes, said receiver including a source of video signals having an output terminal direct coupled to said cathode electrodes and a plurality of sources of color difference signals, each one of which is separately coupled via a capacitor to a separate one of said grid electrodes, said receiver further including a plurality of clamping diodes having one electrode coupled in common and a second separate electrode coupled to a junction between a grid electrode of said kinescope and said capacitor, said common terminal of said diodes being directly coupled to the output electrode of an amplifier device having an input electrode coupled to a source of pulses included in said receiver and developed by horizontal deflection circuitry responsive to a synchronizing interval occurring in said video signal, said pulse as applied to said input electrode of said amplifier device being subjected to variations in amplitude due to undesirable operating conditions of said receiver, in combination therewith, apparatus for controlling the amplitude of said pulse as applied to said common terminal of said diodes, comprising: a. a first source of DC operating potential having a predetermined magnitude, b. a resistor coupled between said first source of operating potential and said common terminal of said diodes, c. a second source of operating potential having a second DC potential magnitude selected in accordance with said predetermined magnitude and different therefrom, d. a unidirectional current-conducting device coupled between said common terminal and said second source of operating potential and biased with respect to said magnitudes of said first and second sources to be normally nonconducting, said unidirectional current device caused to conduct during said synchronizing interval when said pulse as applied to said input electrode of said amplifier device causes the amplified pulse at said output electrode of said amplifying device to reach a DC level substantially equal to the magnitude of said second source, whereby said pulse as applied to said common terminal of said diodes has a magnitude substantially determined by the difference between said first and second DC potential magnitudes, substantially independent of any variations in the amplitude of said pulse as applied to said input electrode of said amplifier device.