Panel Crt
Panel Crt
Why do CRT Televisions make a High frequency sound?
But, Modern day flat panel televisions don't or it is not as much as a crt tv.
What i mean by high frequency sound is that sound from when you turn on your tv i don't know how to explain it but im sure you guys know what im am trying to describe.
The electron beam is guided left and right by a sawtooth waveform applied to a coil of wire. The frequecy of the horizontal trace is 15725 Hz, if I remember correctly. If there is a small or thin enough magnetic object in the vicinity, it will tend to physically vibrate in response to the sawtooth waveform applied to the horizontal deflection coils.
LCDs on the other hand, don't need a magnetic field to scan the display. They do, however, require high voltages to illuminate the often fluorescent backlight. The easiest way is to use a small step up transformer as part of a switch mode power supply, with a variable frequency applied to it to control the brightness, so adjusting LCD backlight brightness may result in a change in pitch of the sound emanating from a tiny transformer
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Kontron CRTtoLCD-6 CRT/DVI Input Flat Panel Controller PN: 21082 $175.00 |
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