Datasheet

52 Chapter 1
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Hardware
Exam Essentials
Learn to troubleshoot overheating issues. When overheating occurs, you need to be
able to isolate the source quickly and respond before the problem affects internal system
components.
Identify problems that can result from overheating. Overheating can cause spontaneous
rebooting or shutdown. Overheating is often caused by nonfunctioning cooling fans or
improper airflow through the PC.
Display Devices
Several types of computer displays are used today, including the TV. All of them use either
the same cathode ray tube (CRT) technology found in television sets or the liquid crystal
display (LCD) technology found on all laptop, notebook, and palmtop computers.
Critical Information
There are two ways of measuring a monitor’s image quality: dot pitch and refresh (scan) rate.
A monitor’s dot pitch is the distance between two dots of the same color on the monitor. Usu-
ally given in fractions of a millimeter (mm), it tells how sharp the picture is. The lower the
number, the closer together the pixels are, and thus the sharper the image. An average dot
pitch is 0.28mm.
A monitor’s refresh rate specifies how many times in one second the scanning beam of
electrons redraws the screen. The phosphors stay bright for only a fraction of a second, so
they must constantly be hit with electrons to stay lit. Given in draws per second, or hertz
(Hz), the refresh rate specifies how much energy is being put into keeping the screen lit.
Most people notice a flicker in the display at refresh rates of 75Hz or lower because the
phosphors begin to decay to black before they’re revived; increasing the refresh rate can
help reduce eyestrain by reducing the flickering.
The resolution of a monitor is the number of horizontal and vertical pixels that are dis-
played. Most monitors allow for two or more resolutions, and you can pick the one to use
in the desktop settings of the operating system. The vertical hold (V-hold) settings can be
tweaked to make the image appear properly in the monitor. Connectors commonly used to
connect the display device include the following:
VGA This is the traditional connector, which is shaped like a D and has three rows of five
pins each, for a total of 15 pins. This is also often called the DB-15 connector.
A 9-pin VGA connector does exist, but it’s very uncommon.
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