| 摘要 |
<p>PURPOSE:To reduce deficiency in a cathode-ray tube and to improve its quality and performance, by detecting a foreign object attached to the shadow mask of the tube while scanning said mask with electron beams, and then concentrating the irradiation of electron beams at the position where the foreign object is attached so as to remove it. CONSTITUTION:A television set circuit 9 including a power source and a deflection control circuit is energized in such a way that a deflection current is applied through each of deflection coils 5, 6, and while thus an electron beam produced in a high voltage generating circuit 7 scans a shadow mask 14 of a cathode-ray tube 12 vertically and horizontally. Where there is a foreign object 15 in a hole of the shadow mask 14, a black spot appears on the face of the tube 12. Removal of the foreign object 15 is carried out by causing the deflection current to be changed by a direct current from a D.C. power source 3 by means of a switching means 4 thereby to control the deflection current through circuits 1, 2 adapted to adjust deflection positions in the vertical and horizontal directions, and then irradiating an electron beam onto the foreign object 15.</p> |
