Free lcd monitor repair ebook

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2. Preface You may distribute this ebook freely. The ebook is illustrated with 40 colorful photos of LCD Monitors. It explains the basic functions, major components and repair guide of LCD Monitor which is required to be fully understood and will be a knowledge channel of being a succesful LCD Monitor repairer. Friendly Reminder The reader is expressly reminded to consider and adopt all safety precaution that might be indicated by the activities herein and to avoid all potential hazards. Although all possible measures have been taken to ensure the accuracy of the information presented, neither Lcdmonitorrepairebook, nor the author are liable for damages or injuries, misinterpretation of directions, of the misapplications of informaiton. By following the instructions contained herein, the reader willingly assumes all risks in connection with such instructions. 3. CONTENT 1. INTRODUCTION: LIQUID CRYSTAL DISPLAY MONITOR 2. HOW THE LIQUID CRYSTAL LIGHT CONTROL 3. DIVISION OF LCD DISPLAY AND TFTS 4. BASIC STRUCTURE OF TFT LCD DISPLAY 5. CONTROL OF TFT LCD DISPLAY TRANSISTORS 6. STRUCTURE OF THE LCD DISPLAY AND BACKLIGHTING 7. BACKLIGHTING OF THE LCD LAMPS 8. HOW TO OPEN THE LCD MONITORS 9. INTERNAL BOARDS OF LCD MONITOR 10.BLOCK DIAGRAM IN LCD MONITOR 11.IDENTIFICATION OF MAJOR COMPONENTS IN MAIN BOARD 12.IDENTIFICATION OF MAJOR COMPONENTS IN POWER SUPPLY BOARD 13.IDENTIFICATION OF MAJOR COMPONENTS IN POWER INVERTER 14.PROCEDURE FOR LCD MONITORS REPAIR 15.DEFECTS IN LCD DISPLAY 16.OTHER DEFECTS IN STEPS OF MONITOR 17.EXAMPLE OF IC REPLACEMENT IN LCD MONITOR 18.PROCEDURE FOR IC REPLACEMENT IN LCD MONITOR 19.COMBINATION OF SCALAR AND MICRO IN ONE IC 4. LIQUID CRYSTAL DISPLAY MONITOR The LCD screen is the equivalent of the picture tube monitors. It consists of several layers and below all have the light diffuser, which is a white plastic plate that distributes the light from two or more cold cathode fluorescent lamps (CCFL) uniformly behind the screen. Also within the module of display drivers find the ICs of the pixels that form images on this display. In the figure below we have a picture of one taken from a display monitor showing in detail the terminals of the CCFL lamps: 5. Important: The LCD display is only one module, so any defect which comes to present, including blemishes, dead pixel, broken glass, light bulb or IC, it should be swapped round, as well as with the conventional tube monitors when they are weakened, the filament burned or going short. HOW THE LIQUID CRYSTAL LIGHT CONTROL:- Liquid crystal is a substance with characteristics between solids and liquids. In solids the molecules are close together and organized structures. Already in the liquid the molecules are far apart and move in different directions. In the liquid crystal molecules are arranged in structures, but not so close as in solids. See below: When a light beam passing through the liquid crystal molecules, its direction is changed. Then just put the plate of liquid crystal between two polarizers, apply tension between them and make the light go through one of the polarizers, through the liquid crystal to reach the other polarizer. 6. Polarizing Filter - glass formed by grooves that only lets the light pass in one direction. The polarizers are placed at the ends of the liquid crystal with the slots at 90 degrees relative to each other. Among them will a source of tension that can be turned on or off. See the structure in the figure below: When no voltage is applied between the polarizers, the light passes through the first and the liquid crystal molecules twist light by 90 so that it can cut through the second and becomes visible in front of the display. So the display is clear. When voltage is applied between the polarizers, the molecules are oriented differently so as not to change the direction of light from a polarizer. Thus the light can not leave the polarizer 2 and can not be seen in front of the display. So the display goes dark. Controlling the level of voltage applied between the polarizers is possible to vary the level of light that pass through the display. 7. DIVISION OF LCD DISPLAY AND TFTs Pixel - is the smallest part that forms the image. Each pixel comprises three subpixels, one red (R), one green (G) and one blue (B). The LCD screen is divided into pixels and subpixels. For example, an SVGA screen has a resolution of 800 columns x 600 rows. Hence it is composed of 480,000 pixels. Since each pixel has three colors, gives then a total of 1.44 million rooms in this screen. Already have an XVGA screen resolution of 1024 x 768, has 786,432 pixels and 2,359,296 divisions. The higher the screen resolution, more divisions it should have. Each division (sub-pixel) screen is controlled by a tiny transistor mosfet mounted on a glass block located behind the LCD. Each of the transistor is called TFT. TFT - Thin Film Transistor "- or thin film transistor is a transistor mounted on a glass substrate. As explained, the LCD monitor has millions of transistors on a glass TFT mosfets located between the polarizer and a liquid crystal block. An LCD screen resolution of 800 x 600 has 1.44 million of these transistors mounted on the glass. Each transistor is responsible for making their subpixel pass the light (on) or block (off). Below is the basic structure shown in the next page: 8. BASIC STRUCTURE OF TFT LCD DISPLAY 9. BASIC STRUCTURE OF TFT LCD DISPLAY Each transistor is driven by the TFT gate line and the line of source pulses through digital level "0" level or "1". When the gate-source and receiving a level (voltage), the TFT is driving and lets light pass through the subpixel, this appearing green, red or blue and clear in front of the screen. When the gate or the source receive level 0 (no tension), the TFT is not conducive and the subpixel is off. For each image formed on the LCD panel, TFT each receives eight bits "0" and "1" each time. If all bits are 1, one subpixel has the maximum brightness. If all bits are 0 subpixel that is off. If some bits are 0 and others are 1, the subpixel is eight times turns on and off very 10. quickly so that our eye sees brightness weaker. Since each subpixel (color) receives 8 bits at a time, he may have 256 levels of brightness. Since each pixel has three colors, multiplying the 256 brightness levels for each one, it follows that this can reproduce 256 pixels (R) x 256 (G) x 256 (B) = 16,777,216 colors, or more than 16 million colors. The capacitors storage to store a few moments of briliance that subpixel information. LCDs are called using transistors TFT active matrix and provide greater vibrancy to the image being used by all computer monitors today. 11. CONTROL OF TFT LCD DISPLAY TRANSISTORS The connection between the LCD and the board of the monitor is made by a connector called LVDS (low voltage differential signaling). Thus the digital data are applied to the display by lines of 0 or 1.2 V providing higher speed transfer of data and no noise. By going through the LVDS connector, the data goes to a driver IC and the display of ICs for various LDI providing the bits to drive the TFT transistors. The display driver IC is located on a plate attached to the glass substrate where are the TFTs. The display driver ICs are connected LDI between the plate and glass substrate. But these components are not replaced when they burn. The solution is to exchange the entire display. See the figure below the location of transistor TFT display driver ICs: On board display also enter a B + 3.3 or 5 V to power the control IC and LDI. 12. STRUCTURE OF THE LCD DISPLAY AND BACK LIGHTING As explained, the LCD is a sandwich of plates and glass substrates, as well as the structure of the backlight. See below: LCD screen is comprised of the following components: Polarizers - Just let the light pass in one direction; Plate TFT - glass substrate where are the mosfets transistors that control the brightness for each individual subpixel; Color filter - glass substrate that gives color to the RGB subpixels controlled by mosfets; Liquid crystal - Modifies or not the path of light passing through it depending on the voltage applied between the polarizing plate by mosfets TFT. 13. Backlight is formed by: Lamps CCFL - cold cathode fluorescent lamps used to illuminate the display. The monitor can have two or more of these; Power inverter - provides between 300 and 1300 VAC to feed the bulbs. By controlling the voltage to the lamp, adjust the brightness of the display; Light guide - Directs light to the LCD display; Spotlight - Reflect light to the guide; Diffuser - spreads the light evenly in the backlight unit; Prisma - Transfer the drive light to backlight the LCD display. Printed circuit board to the LCD display - Contains the display driver IC and IC to provide the LDI bit to drive the TFT. The LCD screen, the backlight unit and printed circuit board form a just and as already explained, with defect in any part of the whole thing must be repla