CRT Display Degaussing
Until recently, most computer displays used a Cathode Ray Tube (CRT). A CRT consists of a glass vacuum tube
with three electron guns (one for each color; red, green, and blue) at one end, and a phosphorous coated
screen at the other end. Where an electron beam hits the screen, the phosphorous glows, creating the image
on the screen. Today most computers use liquid crystal display (LCD) technology for their displays, but there
are still many CRTs around, and they are covered in the CompTIA A+ certification exam.
- Electron guns
- Electron beams
- Focusing coils
- Deflection coils
- Anode connection
- Mask for separating beams
- Phosphor layer
- Close-up of inner side of screen
In the CRT a deflection coil is used to steer the electron beam to a specific point on the screen. Gradually
magnetic fields build up that cause color impurity on the screen. Degaussing, named after Carl Friedrich Gauss,
is the process of removing an unwanted magnetic fields. Most CRTs have a copper coil wrapped around the
front of the display, used as a degaussing coil. Tubes without an internal coil can be degaussed using an
external hand held version.
Most modern CRTs have buttons on the front of the monitor to adjust the image settings. Pressing the Menu
button will bring up a menu of adjustments that you can make to the monitor. If color impurity occurs, press
the Menu button and select the item with the magnet icon to degauss the screen. The actual degaussing
process will temporarily distort your screen.
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