The Most Important Components of LCD Monitors

The screen is a key component in the computer`s system. It allows the computer user to view the results of his operations in a convenient and immediate way. If the screen goes bad, this is a problem that will end the ability to work on a computer.

LCD screens can suffer from various problems, but several symptoms of display problems are quite limited:

• No picture at all, the screen does not show signs of life (sometimes the power light does not come on).
• Screen switches itself off after a certain period of time (short times to a few seconds after start-up).
• The screen shows a very dark, faded picture and a significantly low level of brightness.
• A completely white screen, and the screen doesn’t show any picture at all.
• The screen has a line or a colored vertical lines which aren’t part of the displayed picture.
• The monitor shuts down after a while
• HDMI port doesn’t work, the monitor shows “No signal”
• Takes long time for the monitor to turn on

In order to understand what could cause such problems and how to solve them, one needs to understand the mechanics of LCD (Liquid Crystal Display which is screen-based liquid crystals).

How does the LCD screen work?

CRT (Cathode Ray Tube) monitors are based on a receiver with an electron gun at one end and the electron’s sensitive screen at the other end. The electron gun fires every point on the screen, turns it on (because of the impact point of the electrons) and creates an image on the screen. The mechanics of LCDs are significantly different.

LCD screens rely on several technologies in order to display an image:

1. Polarized glass –  Polarized glass will pass light waves in a certain angle. Therefore more light is blocked. If you put two glasses with the same polarization one after the other, the light will pass through both. If, however, the first glass will have a polarization that is perpendicular to that of the second glass, the light will not go through at all.

2. Liquid crystal molecules – the uniqueness of these molecules is that they are able to pass light through, and are affected by electrical current which changes the way the light passes through the molecule.

3. Transparent conductive materials – electric current is run in LCD screens and should reach every pixel, for this purpose transparent conductors are used. This makes it possible to avoid seeing it on the screen and causing interference with the picture. An example of a transparent conductive material (which is typically used in LCD screens) is indium – the oxide of tin.

4. Backlight – it is lighting sours that is located behind the LCD screen to provide light through LCD pixels. It was customary to use fluorescent lighting in favor of this theory, but in recent years the use of LED lighting in screens rose (which enables lower power consumption and better contrast).

The LCD screen is made up of two glasses that are connected to each other, and a backlight located behind. The glasses are made of liquid crystal molecules, which are designed to be influenced by electric current. They are distorted by 90 degrees (e.g., light enters from one side, leaving a polarized glass at 90 degrees on the other side). If there is no electricity transferred into the molecule, the light that is coming from one side of the screen will not pass through a polarizing glass, otherwise it will be rotated 90 degrees in the molecule and then pass through the second polarizing glass.

When an electric current passes through the molecule at different volumes, it is undergoing varying degrees of deformation and the light is being twisted at an angle between 0 and 90 degrees. This way various shades of gray being delivered. To receive a colored image, arrayed sub-pixels of red, blue and green, similar to the CRT screens need to be added (so, each pixel consists essentially of three sub-pixels that are able to display any combination of red, blue and green, and actually show each color).

What causes LCD screen problems?

Now that it is clearer how an LCD screen works, you will be able to review the problems caused by abnormalities in various parts.

1. Power supply
The power supply is responsible for supplying electric current to every component of an LCD screen. Therefore, any abnormalities will usually cause varies problems in the screen. In addition, if not handled in time may cause the screen to get irreparable. The power supply is a component that can be repaired or replaced in our lab.

2. Backlight
A backlight provides light that passes through the LCD crystals. A backlight uses fluorescent bulbs or LEDs, once it is compromised in one way or another nothing can be displayed on the screen or will displayed faded image. If the backlight will lose its vividness it will cause the screen to display a dark and faded image (because the maximum brightness level decreased significantly). Our lab can replace old bulbs or defective new bulbs and return the LCD screen to life.

3. Inverter
Inverter is a device that provides current to the backlight module. An inverter provides a very high voltage to fluorescent bulbs and much lesser voltage for LEDs. The Inverter sees that all bulbs or LEDs are stable and working, therefore, any irregularity leads immediately to the invertor’s protection module activated and shutdowns backlight. A faulty inverter cannot supply the required current and voltage over time. It is usually responsible for problems connected only with backlight. The screen brightness will be affected, if the inverter cannot supply the current that is needed to run the backlight at full power. The inverter is a component that can be repaired or replaced in our lab.

4. Motherboard of LCD screen
The motherboard is the main component, includes processor that is responsible for decoding the signal which comes from a computer’s graphics card. It also controls an inverter, power supply and the LCD screen. Malfunctioning motherboard can result in all kind of problems with the monitor.

5. Array of liquid crystals
Liquid crystals can be damaged in any way in the LCD screen itself. In this case, the result will usually be dead pixels (pixels that display consistently the same color, regardless of the picture).
There are other problems with LCD screens that are caused by faulty components on the LCD graphics card.

As you can see, most of the problems with LCD screens are caused by faulty components which can be repaired or replaced. This is much cheaper than buying a new LCD screen. Also it is the most economical way.

If you have any questions or are interested in consulting a computer technician please contact us or call 054-225-7705