Picture-Tube Improvement through Controlled Manufacturing Environment and Ultrasonic Cleaning Technologies

Abstract

. The trend toward higher-voltage picture-tube operation requires basic improvements in manufacturing techniques. The threshold of high-voltage instability characteristics of modern picture tubes cannot be increased significantly by design without adversely affecting focus and other performance characteristics. A practical technique of increasing the threshold of highvoltage instability by about 6 kv has been developed by means of extensive revisions of the picture-tube electron-gun manufacturing processes. Reduction of arcing, stray emission, neck fluorescence, and interelectrode shorts and leakages has resulted from the use of ultrasonic cleaning processes and "clean" environments. A precision method of controlling the grid-to-cathode spacing to improve the control of cut-off voltages has been developed. The physical geometry and relatively small size of picture-tube gun components required extensive investigations to determine the most efficient application of ultrasonic cleaning techniques, application of precision-controlled cathodegride 1 assembly technique, effective materials handling and storage methods, and a system for the protection of completed guns from particulate contamination. Concepts of environmental "whiteroom" nature were employed to house the program adequately. The extensive revisions to the picture-tube manufacturing processes and the new equipment and facilities at the RCA, Marion, Ind., plant are described. The performance of picture tubes has been improved continuously during the past few years as a result of improvements in high-voltage stability; reduction of interelectrode leakage; increased cathode emission, stability, and reliability; and the introduction of techniques related to focus quality. The solutions to these problems prompted detailed considerations of all factors affecting the picture tube, particularly gun processing and environmental controls during manufacturing. RCA, in the Marion, Ind., plant, has developed a new "total concept' approach to the solution of f Electron Tube Division, RCA, Marion, /rid. these problems based on a micro-clean processing program designed to produced economically manufactured electron guns properly processed for maximum reliability,