Service switch arrangement for low level matrixing type television receiver
AssigneeZenith Radio Corporation
InventorFred D. Johnson
Life of this patent
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Abstract
A service switch arrangement for a color television receiver having a low level matrixing system developing red, blue and green color signals includes a service switch having a normal position and a service position. In the normal position of the switch, a video output amplifier is enabled for coupling the red, blue and green color signals to the electron gun cathode elements of a color cathode ray tube. In the service position of the switch, the video output amplifier is disabled while an independently generated DC control voltage is coupled to the electron gun cathode elements for facilitating adjustment of the cut-off points of the cathode elements.
Claims9
In a television receiver of the type having a low level matrixing system developing red, blue and green color signals and a high level output amplifier including a plurality of stages each coupling a respective one of said color signals to a cathode of a color cathode ray tube, the improvement comprising:
- switch means having a first terminal connected to a source of ground potential a second terminal connected to a high level supply of DC voltage and a common terminal, said switch means including an operating member having a normal position interconnecting said second and common terminals and a service position interconnecting said first and common terminals;
- means coupled to said second terminal for developing a DC control voltage having a value less than said high level DC supply voltage;
- and
- circuit means coupled to said common terminal and to said control voltage developing means, said circuit means being responsive to the normal position of said operating member for enabling the operation of each of said output amplifier stages and responsive to the service position of said operating member for inhibiting the operation of each of said output amplifier stages while coupling said control voltage to each of said cathodes for facilitating the adjustment of the cut-off point of said cathode ray tube.
In a television receiver of the type having a low level matrixing system developing red, blue and green color signals and a high level output amplifier including a plurality of output transistors each coupling a respective one of said color signals from its collector terminal to a cathode of a color cathode ray tube, the improvement comprising:
- switch means having a first terminal connected to a source of ground potential, a second terminal connected to a high level supply of DC voltage and a common terminal, said switch means including an operating member having a normal position interconnecting said second and common terminals and a service position interconnecting said first and common terminals;
- means coupled to said second terminal for developing a DC control voltage having a value less than said high level DC supply voltage;
- and
- circuit means coupled to said common terminal and to said control voltage developing means, said circuit means being responsive to the normal position of said operating member for coupling said high level supply of DC voltage to the base and collector terminals of each of said output transistors for enabling the operation thereof and responsive to the service position of said operating member for coupling said source of ground potential to the base terminal of each of said output transistors for inhibiting the operation thereof while coupling said control voltage to the collector terminal of each of said output transistors for facilitating the adjustment of the cut-off point of said cathode ray tube.
Dependencies are inferred from the claim text.