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CRT Phosphor Protection Circuit

IP.com Disclosure Number: IPCOM000051804D
Original Publication Date: 1981-Mar-01
Included in the Prior Art Database: 2005-Feb-11

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Marple, WP [+details]


In conventional CRT displays, the grid voltage is typically grounded and the video amplifier input to the cathode is modulated from ground potential to approximately a +50-volt level. If a defect occurs to both the horizontal and vertical deflection amplifiers for the CRT, the electron beam will be focused on the center of the display face and can burn phosphor at the point of incidence. Alternately, if a video amplifier failure occurs so that the cathode of the CRT assumes a relatively negative potential with respect to the normal black level potential, the phosphor on the face of the tube can be damaged.