NOTES ON MONITORS

Each of the three CRT guns emit an electron beam which activates the red, green, and blue phosphor dots. The beams scan one horizontal row (raster line) to activate these dots until they reach the end of the screen. At higher screen resolutions, some monitors skip every other row on a pass, scanning the odd numbered rows in one pass, then doing a second pass to scan the even numbered rows.. This type of two pass scanning is called interlacing. Monitors that scan all the raster lines in a single pass are Noninterlaced monitors, and generally produce a better high resolution image than interlaced monitors. 

The measure of how many horizontal lines the beams can sweep in one second is called the horizontal scan rate or the horizontal frequency and is measured Khz (thousands of cycles per second). The measure of how fast the monitor can draw a full screen from the upper left corner to the lower right corner is called the vertical scanning frequency or the refresh rate and is measured in Hz (cycles per second). 

A quick way to measure the quality of a monitor is to note the number of controls. Look for at least six… Vertical and horizontal position, vertical and horizontal size, brightness and contrast. 

From a Cambridge, England Professor

The Cathode Ray Tube (CRT) is used in oscilloscopes, radar, monitors and television receivers. 
It consists of a glass envelope made from a neck and cone.  
All air has been extracted so that it contains a vacuum. 

At the narrow end are pins which make connection with an internal ELECTRON GUN. 
Voltages are applied to this gun to produce a beam of electrons. 
This electron beam is projected towards the inside face of the screen. 

The face is coated with a PHOSPHOR which PHOSPHORESCES (glows) when hit by the beam. 
This produces a spot of light on the centre of the face of the CRT. 
By varying the beam current, spot BRIGHTNESS can be controlled. 
Controlling the diameter of the beam controls FOCUS. 

Phosphors come in a range of colours. 

On its way from the gun to the screen the beam passes between  2 sets of plates. 
They are called the X and Y plates (as in graphs). 
By applying voltages to these plates the beam can be deflected. 
This causes the spot to move from the centre of the screen to another position on the screen. 
The X plates plates deflect the spot horizontally, the Y plates vertically. 
Thus the spot can be deflected to any position on the screen. 
External deflection coils are often used instead of the internal deflection plates. 

Note that dropping a CRT causes it to IMPLODE which is as dangerous as an explosion.
 
 
 

From Sony site.............

Question:  I have just noticed a thin gray line on the image displayed by my Sony computer monitor. It is about one-third of the way from the bottom of the screen. Is this normal? 

 Answer:  This is normal. What you are seeing is the shadow cast by the horizontal damper wire used to stabilize the aperture grille featured on all Sony Trinitron picture tubes. 

Currently, there are two display technologies designed to isolate individual picture elements (pixels). Together, these pixels form the image displayed on a computer's monitor.  Shadow mask technology relies on an opaque sheet with small pinholes to separate pixels both horizontally and vertically. Aperture grille technology employs a series thin, closely-spaced vertical wires to isolate pixels horizontally. The pixels are separated vertically by the nature of the scan lines used to compose the image. 

There are two main advantages of the aperture grille method. The most visible is that this method allows more electrons through, resulting in a brighter image with better contrast. The second advantage is that the monitor's vertical resolution is not dependent upon, nor affected by, the vertical spacing of pinholes. A third advantage of an aperture grille is that it is much less susceptible than a shadow mask to warping caused by heat. To keep the vertical wires in an aperture grille properly aligned within the picture tube, one or two horizontal damper wires are required. A 14-inch or smaller Sony computer monitor employs one such wire. It is located about one-third of the way from the bottom of the screen. Sony computer monitors larger than 14 inches use two horizontal damper wires. These wires are located roughly one-third of the way from the top and bottom of the screen. Each wire casts a faint shadow that is visible as a light gray, horizontal line on the image. This shadow is normally not visible, but may become apparent when displaying a lightly-colored background. 
 

Question:  What is Multiscan Technology? 

Answer: Multiscan Technology enables a monitor to self-adjust to video signal from a variety of graphics boards. This makes it possible to switch between graphic modes without user involvement. 
 

Question:  What is difference between Trinitron technology and Shadow Mask technology? 

Answer:  The Trinitron technology uses an aperture grille. This grille, designed with long, unbroken slits, allows more light and color to reach the screen, resulting in purer and more colorful images. The Shadow Mask uses a mesh-like, darker screen that creates a color shift ("doming") distortion and prevents color purity.