Admiral Corporation

Blayne E Arneson

There is disclosed a simplified bias and gain adjust system for a color cathode ray tube wherein, by a minimum of adjustments, the bias for an in-line color cathode ray tube may be adjusted to achieve color balance between the CRT's three electron guns and to achieve a maximum voltage difference between the CRT's G.sub.2 electrode and the cathode element of the dominant electron gun of the color CRT. In particular, the system includes a chrominance matrix amplifier including an amplifying element in the form of a transistor for each of the color-difference signals provided by the chrominance demodulator(s) of the color television system; the color-difference signal is applied, illustratively, to the base of each such transistor, and a luminance signal Y is applied to the emitter of each such transistor element. In particular, first and second supply voltages are applied, respectively, through a first fixed resistor and a second variable resistor to each transistor's collector the second voltage source being less than the first-mentioned voltage source. By varying the second-mentioned resistor element, the load and therefore the gain of the transistor, as well as the effective supply voltage developed at the transistor's collector, are established. In an embodiment wherein such an amplifying circuit is adapted for a three-gun cathode ray tube, a common, second variable resistor is interconnected between the collectors of at least two of the driver transistors and is adjusted to differentially control the gain and the supply voltages of the two driver transistors.

Simplified bias and gain adjust system for color cathode ray tube

There is disclosed an AFT summing circuit for a varactor-type tuning system and in particular for such a tuning system including a UHF tuner and a VHF tuner. A tuning voltage derived from a suitable source indicative of the desired channel or station to be tuned is applied to one input of the AFT summing circuit, while an error signal as derived from an AFT circuit is applied to the other input, to be summed together in a manner whereby the effect of the AFT signal may be adjusted without affecting the tuning voltage. The AFT circuit output is applied at a first level when the VHF tuner is operative, and at a second attenuated level when the UHF tuner is operative. In particular, the AFT summing circuit includes first and second impedance elements for applying the AFT circuit output to first and second input terminals of an operational amplifier, and a third impedance element for applying the tuning voltage to the second input terminal. A fourth impedance element is connected in a feedback loop from the output of the operational amplifier to the first input terminal. The values of the first, second, third and fourth impedances Z.sub.1 , Z.sub.2, Z.sub.3 and Z.sub.4 are selected to satisfy the following equation in order that a substantially predetermined gain is provided to the tuning voltage, regardless of the adjustments made to the AFT circuit output: ##EQU1## Further, there is included means for applying a variable control or gain to the correction signal component of the output of the operational amplifier.

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Evergreen Park, IL, United States of America

Blayne E Arneson