tv noise (1 Viewer)

[denis d]

a month ago I remove the back panel of my tv to clean inside.after the clean up I screw back the panel and now I hear a high frequency noise from it. where this noise come from ... can I fix it. thank you!

 

[Allan Jayne]

There are things in a TV that vibrate due tot he electronic signals and currents that are involved. One is the "flyback transformer" that handles the back and forth scanning of the electron beam at approx. 15.75 KHz for regular NTSC interlaced video. Actually lots of TV sets emit that high pitched frequency while lots of people can't hear that high.
A 60 or 120 Hz hum is also heard from time to time because parts inside a power transformer shrunk due to age and now vibrate. So called full wave rectification which is the rule instead of the exception produces a 120 Hz current that can also lead to audible hum.
It is hard to say what you loosened up inside your TV while cleaning so that some vibrating part is either vibrating more or touching and transmitting the vibration to some other part that accentuates the noise. A small light foreign object such as the wing of an insect that fell inside, can amplify high frequency noise (tweeter cones are small, you know).
Video hints:
http://members.aol.com/ajaynejr/video.htm