IBM Technical Disclosure Bulletin (TDB 07-81 p1148-1149)
English (United States)
2 pages / 41.1 KB
CRT Assembly Noise Reduction
Elimination of high frequency noise pollution emanating from a cathode ray tube (CRT) display assembly is of critical concern to individuals using data processing equipment. Typically a CRT display operates with a horizontal drive frequency within the audible range, such as in the 15 to 16 KHz range, and it is this frequency that must be eliminated.
The CRT horizontal deflection yoke and the high voltage flyback transformer work in conjunction to produce the horizontal deflection. It has been determined that the flyback transformer is the major cause of the noise pollution and that the acoustical insulation of a typical machine cover does not contain this noise since at these frequencies the noise emanates through the machine louvers.
One effective method of eliminating some of this noise is to mount the flyback transformer on a mitigating material, such as a composition cork and rubber pad. Referring to the figure, a transformer 10 is mounted to frame 12 by using two composition pads 14 positioned on both sides of frame 12. Transformer 10 is then secured to the frame by nuts 16 and washers 18 in a known manner. This manner of securing transformer 10 to frame 12 eliminates that part of the radiated sound resulting from the metal-to-metal contact, which is sufficient to reduce the total noise from an unacceptable level to an acceptable level.