penguinman said:
yep, magnets affect the vaccuum in tv sets.. or the electrons.. i dont know the technical stuff, but magnets (found in all speakers) discolor tv sets and monitors
OK, for all you whippersnappers, listen up. A CRT (Cathode Ray Tube) as found in most TVs (other than plasmas, LCDs and LCD/DLT projection units) and in tube-style computer monitors (that's what your dad used, son, before there were LCDs) consists of an electron gun, a deflection yoke, a mask or grille, and a phosphor target (the inside of the display glass). The gun shoots electrons toward the target, the deflection yoke (electromagnets) aim the beam of electons by bending it with magnetic deflection, the electrons are masked by the shadow mask (or wire grid, in a Trinitron design) to break them up into discrete pixels, in patterns of red, green and blue circles or stripes. The phosphors on the target glow when hit by the beam.
The deflection yoke scans the electron beam down the screen in a zigzag pattern very rapidly, as the gun fires at the appropriate time for each pixel that is wanted to be lit.
Since magnets are used to aim the electons, what is happening when you bring a powerful magnet near a CRT is that the magnetic field deflects the electron beam in its path to the phosphors: this causes colour change, or fringed patterns of colours on the screen 'coz the electrons are now hitting the wrong pixels.
LCDs are not affected because they use direct transistor control over each pixel on the screen, so they don't rely on magnetic aiming and focussing of a beam.
If you leave a magnet near a CRT too long, the shadow mask can become permanently magnetized itself, and persist in distorting the picture after you have taken away the magnet -- you've seen a "de-gaussing" button or menu control on monitors? That is a de-magnetizing procedure that removes the effects of redsidual magnetization of the internal components. Plus it makes a cool noise and light show whgen you press it.
