what's the high pitch whistle crt telivisions make when their turned on (especially old ones)?

Answer 1

The sound is from the horizontal sweep frequency of approz 15kHz; it is near the upper range of human hearing, so many people (especially older people) cannot hear it. The sound itself (if it is loud) comes from what is called the horizontal flyback transformer which generates the high voltages needed for the CRT. This transformer generates strong magnetic fields that can cause its metal components to vibrate at the horizontal sweep frequency. Sometimes as the set ages, some parts get loose and make more noise when they vibrate. Non-CRT TV sets do not have deflection circuits and do not need high voltages, so they do not have this problem.

Answer 2

Doing some research on the CRT (i.e. cathode ray tube) design
should give you some insight as to why it makes this noise...

H a p p y
V i e w i n g !