Temperature compensation of shadow mask color picture tubes

This paper discusses several methods of temperature compensation for shadow mask color television picture tubes. During tube operation, the shadow mask consumes as much as 20W of energy due to bombardment by the electron beams. Thus, the masks run about 200°C above the temperature of the glass envelope. This produces for the various tubes a maximum thermoexpansion in the order of 0.0025 inches. This results, of course, in beam landing shifts of a similar order of magnitude. It will be seen that by moving the mask closer to the screen a similar amount, this shift can be prevented. It will also be seen that a three-point suspension can be made without translation of the mask due to temperature change in the mask and spring mountings. Thus, the advantages of three-point definition can be utilized without any drawback. The method used is superior to the prior art, since it is the only design approach that produces a movement which is solely coaxial with the central axis of the tube; and no element is allowed to rotate on another element. Thus, frictional losses which vary widely from unit to unit are totally eliminated.