| 摘要 |
A system for preventing phosphor burn in a cathode ray tube (CRT) without a shadow mask such as used in a projection television receiver is disclosed. Horizontal drive circuit failure or the intermittent operation thereof is detected by means of a fast falling, horizontally derived, high voltage sweep transformer output which results in the application of a stable positive voltage to raster blanking circuitry for the duration of horizontal drive circuit failure or intermittent operation. Short time constant coupling circuitry permits the near simultaneous shutdown of the CRT upon detection of a horizontal drive circuit malfunction in avoiding the burning of a vertical line on the unprotected phosphor-coated faceplate of the CRT.
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