Abstract: A cathode ray tube may utilize a focus mask color-selection structure. The focus mask structure is susceptible to localized, transient short circuit events, or breakdown events. These events may be caused by conductive particulates that become free within the cathode ray tube and provide a short circuit between first and second layers of the focus mask. The breakdown events are undesirable because they may result in cross-strand currents causing mask strand magnetization that can interfere with a video image on the screen of the cathode ray tube. A transformer rapidly senses random changes in a voltage or a current supplied to the second layer of the focus mask. A pulse waveform generator is coupled to the transformer and provides a pulse waveform responsive to the sudden change in voltage or current.

Abstract: A cathode ray tube may utilize a focus mask color-selection structure. The focus mask structure is susceptible to localized, transient short circuit events, or breakdown events. These events may be caused by conductive particulates that become free within the cathode ray tube and provide a short circuit between first and second layers of the focus mask. The breakdown events are undesirable because they may result in cross-strand currents causing mask strand magnetization that can interfere with a video image on the screen of the cathode ray tube. A rapid degaussing operation is initiated during the next subsequent vertical blanking period following detection of the breakdown event.

Abstract: The present invention provides a method of making a tensioned focus mask. Such a mask includes a set of parallel strands and a set of parallel wires that are perpendicular to the strands and separated from the strands by insulator means. The method includes attaching the strands to a mask frame and then coating the strands with a first insulator. The first insulator is then cured, and a second insulator is applied to the first insulator. Next, wires are wound over and in contact with the second insulator, by rotating the mask frame and by drawing a continuous wire from a source through a tensioner, while guiding the continuous wire into desired positions overlying the strands. Finally, the second insulator is heated until the wires attach to the second insulator.