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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.



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



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:



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.



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.



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:



BASIC STRUCTURE OF TFT LCD DISPLAY



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



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.



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.



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.



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 replaced.

BACKLIGHTING OF THE LCD LAMPS

As explained the lighting is done with cold cathode fluorescent lamps

(CCFL). These lamps have a glass tube containing inert gas inside (neon,

argon and mercury), two domestic terminals called cathode and a layer of

phosphor on the inside walls of glass. Applying a high voltage between

cathodes, the internal gas is ionized and emits ultraviolet (UV). The UV

excites the phosphor into visible light which then produces the tube lamp.

For prolonging bulb life it should work with AC voltage. If it also turns on

voltage, but with time the gases accumulate in the corners of the lamp,

darkening them and producing an uneven light in these regions relative to

the rest. See diagram these CCFL lamps fed with AC voltage and

continuous



The CCFL lamps are fed with alternating voltage 300-1300 V which is

obtained by a power inverter. This inverter consists of transformers,

switching transistors and oscillator IC working at high frequency (between

40 and 80 kHz). The inverter then becomes a voltage low between 12 and

19 V on a high alternating voltage to light the lamps. The power inverter is

very easy to find on the monitor. Just follow the wires of the lamps (two

cables for each). The board where they are embedded is the power inverter.

Below is the location of the power inverter of an LCD monitor:



In the power inverter also enter a control signal coming from the board of

the monitor to control the voltage supplied to the lamps and thereby adjust

the screen brightness. Also enter a control signal to turn off the lamp in

case of fault in the system such as the burning of the lamps of the display.

HOW TO OPEN THE LCD MONITORS

Most LCD monitors have locks on the cover of which should be released

for opening the housing. We take great care not to break these locks and /

or knead the monitor case to try to unlock using screwdrivers or other metal

objects. After removing the screws the lid open a crack between the lid and

the front of the monitor. Enter this hole a piece of card or wood phenolite.

Drag wood or phenolite forcing the crack slightly regions where the locks

are going until they drop. After just remove the cover. Below is a sequence

of disassembly of an LCD monitor "Samsung" shown in the next page:



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INTERNAL BOARDS OF LCD MONITOR

By opening a monitor this board find a motherboard on the LCD. We also

find a label attached to lamps of the display. This is the power inverter

board. There are cases where the inverter is on the board to alternate the

power supply voltage monitor. We will also have the card on the main

keyboard connected via a connector. Some monitors will find a board

where it enters the AC cord. This is the power supply board. Below is an

LCD display showing dismantling their boards:



BLOCK DIAGRAM IN LCD MONITOR

In the diagram below we see how to divide the block of LCD monitors and

then have the function of its circuits:

DB15 - This is the same as conventional monitor. Carries the RGB signals

and synchronization to the monitor. Pins 1,2 and 3 receive the signals

coming from the analog RGB video card from the computer and send them

to the scalar IC. 13:14 The pins receive the synchronization signals and

send them along with the micro communication DDC (display data

channel) coming from pins 12 and 15. The function of the DDC is to make

the computer recognize your monitor model and install any drive for better



performance.

DVI connector - This is optional and carries the video signal has already

scanned the computer monitor. Recalling that the LCD monitor is digital,

unlike conventional analog that is. Thus the reproduced image has higher

quality than that imposed by the DB15 connector. The disadvantage is that

the DB15 video card in the computer must convert the digital signal to

analog and the monitor switch from analog to digital again. In this process

there are losses in the video signal, which does not happen when using the

DVI connection between the computer and LCD monitor.

Scalar IC - The largest and main SMD IC LCD monitor. It receives the

RGB signals coming from the DB15 connector or the DVI digital video and

converts them into digital signals suitable for the production of images on

the LCD. The scalar provides signals corresponding to 60-75 complete

frames per second for the LCD display. The signals are transferred to the

display with an LVDS connector. Inside the scalar is going SDRAM

storing the images processed by the complete IC. Hence the IC reads each

image and release this data quickly to the LCD display. This IC also

converts the analog RGB signals into digital DB15 connector and makes

the contrast control and other necessary corrections to the image before

sending them to the display. The IC is controlled by micro scalar. A flaw in

scalar lets the monitor with the screen lit but no picture.

LVDS - "Low voltage differential signalizing" traffic or low voltage

differential signals - is a connector with means of 0 or 1.2 V that transfers

digital signals from the scalar of the display at high speed and with minimal

noise.



Micro IC (or MICOM) - Go on the keyboard and the monitor controls

functions such as brightness, contrast, etc. It is a SMD IC and goes on the

scalar to control the contrast and the rate of transfer of images per second

for the display (resolution). The microcomputer is also connected at the

power inverter to connect, disconnect and control the brightness of the

display lamps. On some monitors the computer is with the scalar in a single

IC. The EEPROM stores the data display control.

Clock - a clock signal is produced from a quartz crystal. It is necessary to

synchronize the data transfer between digital ICs. Without the digital clock

ICs do not work.

LCD display - Converts signals from the scalar in images. As seen the

display receives a complete picture at a time scalar. Are 60-75 frames per

second depending on the rate chosen under Windows. In the display

module for the IC and control ICs that trigger the LDI transistors TFT.

Power Inverter - Transforms + B between 12 and 19 V in voltage

alternating between 300 and 1300 V for lighting lamps CCFL display. It is

controlled by computer.

Power supply - Transforms the alternating voltage network (110 or 220 V)

continuous power in the operation of the monitor. Usually provides a B + 5

V for the LCD and the motherboard which will then be covered in 3.3 and /

or 1.7 V to power the scalar and the micro, and another B + between 12 and

19 V feed the inverter board.



IDENTIFICATION OF MAJOR COMPONENTS IN MAIN BOARD

In the photo below we have the motherboard on a Samsung monitor

highlighting its main parts:

First find the two largest SMD ICs. The biggest is the Scalar and the

smallest is the Micro. Even the latter is near the keyboard connector and the

IC has EEPROM of eight terminals on the side. Near the Scalar have the

crystal clock. On one side we have the Scalar DB15 connector that carries

the signals to the monitor and the other end are the outputs for LVDS LCD

display. Near the source we have the connector IC voltage regulators and

their electrolytic filter. The regulators provide B + 3.3 and 2.5 V to power



the scalar, micro and LCD display.

Mosfet IC - It's a switcher mosfet regulator or mounted inside an IC

containing various terminal source and drain terminal and a gate to control.

In that way we get a good heat dissipation in a small space. This

component type is common in LCD monitors.

IDENTIFICATION OF MAJOR COMPONENTS IN POWER

SUPPLY BOARD

In the photo below we have the power supply board on a Samsung monitor

highlighting its main parts:



After the entry of the power cord have a coil and some large capacitors.

Are network filters that let the system voltage enter and leave the frequency

of the power switch out to not interfere with other devices. The following is

the fuse, bridge rectifier and electrolytic main filter. After this we have the

power switch formed by the IC oscillator and switching device, the chopper

transformer, rectifier diodes and the electrolytic filter the rows of B +

which will feed the circuits of the monitor.

IDENTIFICATION OF MAJOR COMPONENTS IN POWER

INVERTER

In the photo shows in the next page is the circuit of a Samsung monitor at

the top and bottom of PCB.

We located a large transformer in the middle of the plate. It provides the

AC voltage to power the lamps of the display. We can observe that the

connector on both lamps are connected in said transformer. Sometimes

there are two transformers, one for each lamp (in the case of the display

using two bulbs). The primary of the transformer is going on in two

transistors (typically MOSFETs) that turn on and off the winding in the

frequency 40-80 kHz. So the transformer transfers a large alternating

voltage to the secondary (which has more turns than the primary). This

potential difference will light the lamp. The mosfets are controlled by an

oscillator IC. The power inverter circuit is controlled by micro

motherboard, as well as the oscillation frequency to adjust the brightness of

the lamp.

Take care not to touch the welds on this card when it is energized. The

shock at high voltage is not fatal, but it hurts a lot.



PROCEDURE FOR LCD MONITORS REPAIR

This is the part that everyone was expecting. The procedures to fix these

types of monitors. Before we classify the defects into two groups: those

related defects in the display and connected with other circuits, in some

cases may also be on display.

DEFECTS IN LCD DISPLAY

They are usually failures requiring complete replacement of the display.

The LCD Monitor’s failures are caused by one or some transistors TFT

burned, or IC lamp burned on the display board or the breaking of glass or

spots on the display. See the figure below some defects related to display:

For the stained glass screen solutions, click this ebook photo for detail, or access to the following web site http://www.lcdmonitorrepairebook.com/lcdmonitorrepair.htm



For the dead pixel solutions, click this ebook photo for detail, or access to the following web site http://www.lcdmonitorrepairebook.com/lcdmonitorrepair.htm



For the horizontal or vertical bar solutions, click this ebook photo for detail, or access to the following web site http://www.lcdmonitorrepairebook.com/lcdmonitorrepair.htm



OTHER DEFECTS IN STEPS OF MONITOR

In the figure below we have some symptoms of defects in LCD displays.



For the no led, no signal, dark image or dim solutions, click this ebook photo for detail, or access to the following web site http://www.lcdmonitorrepairebook.com/lcdmonitorrepair.htm



EXAMPLE OF IC REPLACEMENT IN LCD MONITOR

Below is an example of a fairly common defect in the lines of monitors

Samsung 510N, 540N, 710N and 740N. Appears only one square that is

passing across the screen indicating lack of signal on the cable (even that

attached to the computer) or resolution error. This failure occurs because of

an internal program error occurred in micro IC. In this case, the solution is

the replacement of the IC and SMD as we take some care in this procedure.



PROCEDURE FOR IC REPLACEMENT IN LCD MONITOR

REPLACEMENT OF SMD IC

We will need the following materials:

- Soldering iron 30 W or 40, fine tip and very clean;

- Solder joint quality such as "Best" or "Cobix"

- Welding of low melting;

- Flow weld pitch (+ isopropyl alcohol);

- A piece of wire mesh or failing that a stalk pickled;

- Isopropyl alcohol to clean the plate;

- Brush teeth;

- Piece of cotton cloth (old t-shirt kind of mesh).

1 - Purchase a new IC with the exact same code that to be changed,

especially for PCs. Parts for LCD monitors can be found at your nearest

specialty stores.



2 - Spread the low-melting solder all pins of the IC that will be replaced.

Take care not to exaggerate the amount of soldering. Then using the tip of

the soldering iron to solder heat evenly on all pins of the IC. Using a small

screwdriver to lever up the IC card so that it falls on the bench. Then

remove the remains of the plate with the solder iron tip. On the trails of the

board where the IC soldier was cleaning can be done with wire mesh:

Spread flow of solder on the tip of the loop, pull it on the trails. Place the

tip of the iron in the mesh and the heat this will attract the remains of

soldiers who were on the trails. Then clean the rest of the plate with a

toothbrush, rubbing alcohol and cloth shirt. See below the IC has

desoldered from the board:

3 - Correctly place the new IC on the tracks of the board and apply solder

joint on the pin ends of the IC, do not worry about the pins that get shorted.

The purpose of this operation is to set the IC on the board.



4 - Apply a small amount of soldering flux on one side of the IC. Make a

big ball of solder on the pins of the tip on this side where it was applied to

the stream. Lift the plate and slide the tip of the soldering iron pulling the

weld down. The solder will come down, solder the pins on the tracks and

because the flow will not be between two pins. If you happen to be two or

more pins stuck can unglue them using wire mesh embedded in the stream,

flush against the pins stuck, heating and so it attracts the solder unwinding

short. See the figure below the IC again already on the board and the

monitor back to working order:



NOTE FINAL

The Micro IC LCD monitor also often called MiCOM or MCU and some

more modern monitors along with the scalar is a single chip. Below is an

example of a chip 100 terminals used by modern LCD monitors from LG

and it has the scalar and micro together shown in the next page.



COMBINATION OF SCALAR AND MICRO IN ONE IC

This is example of Single IC of Scalar and Micro’s combination.



My dear reader,

Here is the end of ebook which covers the basic knowledge of LCD

Monitor repair guide.

For further information, you may buy this ebook which reveals much more

secrets of LCD Monitor Repair in quick and easy way. Imagine how fast

you trouble-shoot the faulty LCD Monitors and receive money from your

customer. It is our recommendation to continue upgrade your LCD Monitor

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