Abstract: According to the prior art, springs (11/18) of a combination mask/frame (10) of picture tubes are joined to the frame by resistance welding. This welding technique is also customary when one of the springs (18) has a centering washer (20) at its free end. When combination mask/frames (10) designed in this manner are snapped repeatedly into and out of the shielding case (15), and when the shielding case (15) is stabilized or fritted to the neck of the picture tube, it can happen that the expansion characteristics of the combination mask/frame (10) are not homogeneous at the fourth spring (18) as compared to the other springs (11) under the picture tube's operating conditions.

Abstract: To prevent the formation of a corona (2) in a known in-line color picture tube with an automatic-focusing deflection system and four grids (G1-G4), a rectangular opening is provided on the side of the second grid (G2) facing the first grid (G1). As a result, the luminous spot (1) formed by the electron beam at the center of the screen is converted to a vertical ellipse and the ratio of the axes of the lateral ellipses on the edge of the image is reduced, thus improving the sharpness of the edges. The openings (5) in the first grid (G1) are elongated in the in-line direction, in particular rectangular, the adjacent openings of the second grid (G2) are also rectangular and all the other openings in the other grids (G2, G3, G4) are circular. In this way, the ratio of the axes of the luminous elliptical spot (11) produced by the electron beam at the center of the screen is reduced without adversely affecting the sharpness of the edges.