TV giving off high pitch hum.
Well I recently inherited a old TV it is an SDTV and it is about seven years old. So I decided to test it with my computers osciloscope and using the microphone on it i turned the osciloscope on and there was one constant signal that went up and down about 3 or four KHZ every second or two. But when I muted the TV their was the normal background noise at about 1-7 KHZ but one signal that I found is about 16-17 KHZ and 5.94 DB, and when I turn the TV off it stops and that 16-17 signal disapers. So how do I get rid of this annoying high pitch noise?