Do-it-yourself lcd monitor repair

If your monitor is broken and does not work, you can try to repair it yourself, while gaining useful practical skills and reducing the costs of your wallet. What do we need for this. First, you must have at least minimal knowledge of electronics and electrical engineering. Secondly, be able to solder correctly. And finally, to carry out a successful repair of a computer monitor, you need to know its structure and the principle of operation of various electronic units of a modern monitor. In addition, you need to be able to properly disassemble the monitor, so that you can then assemble it. So, let's begin.

It is enough just to look at the monitor and understand that this is a complex device consisting of different units and blocks. As immediately striking, the main unit of a modern monitor is a liquid crystal panel or matrix.

LCD Matrix Monitor Repair

The LCD matrix of a monitor is usually a ready-made device, if it breaks down or is mechanically damaged, repairs are usually not required, only the LCD panel is replaced, only in some cases it makes sense to repair it.

As we can see on the back of the LCD, there are many connectors and a PCB for controlling the monitor backlight, which is hidden behind a metal bar. The main element of the board is an image forming microcircuit, a cable leaves the board, which can also cause damage to the monitor.

Monitor interface board

In service manuals, it is usually designated the main board - the main board, in the photo above it is on the right with connectors for connecting to a computer. The board itself houses two eight-bit microcontrollers. The first of these is the Control Processor, which is connected via the I2C bus to the 24LCxx series memory. The second microprocessor is a monitor scaler, it is designed to process an analog video signal and transmit it in digital form to an LCD panel. It also performs secondary tasks associated with scaling the video image, forming the display menu, processing analog RSL signals and many other functions.

An indirect sign of a monitor scaler defect is an incorrect display of the image on the monitor screen, possible artifacts and stripes on it. Sometimes the problem disappears after the microcontroller pins are soldered, and sometimes after some time the problem reappears and then it is necessary to replace the board or a very difficult operation to re-solder the microcontroller.

Monitor power supply. Repair and troubleshooting

The most frequently out of order and, accordingly, the element that most often requires repair is the switching power supply unit of the monitor.

The power supply unit of a modern LCD monitor consists of two parts. The first is an AC / DC adapter and the second is a DC / AC inverter. AC / DC adapter is designed to convert AC mains voltage into a small DC voltage, usually about 12 volts, but not at all

The DC / AC inverter is also intended for converting, but already direct voltage into alternating voltage, but already with a different ordinal value of about 600 - 700 V and a frequency of 50 kHz. High voltage is applied to the electrodes of the fluorescent lamps located in the matrix.

Most switching power supplies today consist of special microcircuits and controllers.

For example, this monitor power supply uses the TOP245Y microcircuit.

In the documentation for the TOP245Y microcircuit, you can find typical examples of power supply circuit diagrams.This can be used when repairing power supplies for LCD monitors, since the circuits largely correspond to the typical ones indicated in the description of the microcircuit.

The TOP245Y microcircuit is a complete functional device in which there is a PWM controller and a powerful field-effect transistor, switching at a high frequency reaching hundreds of kilohertz.

When repairing and eliminating defects, first of all, it is necessary to pay attention to oxide capacitors and it is advisable to check them. In addition, the rectifier very often fails, which is also easily checked with a conventional multimeter in continuity mode in accordance with the diagram.

Monitor inverter and repair

The inverter performs the following functions in the monitor:

The principle of building a modern monitor inverter is shown in the block diagram below, this diagram is suitable for all inverters, which simplifies the process of their repair

The block for sleeping and turning on the inverter is built on the keys Q1, Q2. which translate the monitor into operating mode after 2 ... 3 s. The switch-on voltage is supplied from the interface board and the inverter is rebuilt into operating mode. The same keys switch off the inverter when the monitor switches to any power saving mode.

The brightness control unit of the backlight and PWM lamps receives the dimmer voltage from the interface (main board) monitor board, after which it is compared with the OS voltage, and then a signal is generated that controls the PWM pulse repetition rate.

These pulses are needed to control a DC / DC converter (1) and synchronize the operation of the converter-inverter. The amplitude of the pulses is constant and depends only on the supply voltage, but their frequency varies with the brightness voltage and the level of the threshold voltage. DC voltage from the DC / DC converter is fed to the generator.

The auto-generator is turned on and controlled by PWM pulses.

The protection node (5 and 6) monitors the voltage and current at the output of the inverter unit and generates feedback (feedback) and overload voltages. If the value of one of these voltages, for example in the event of a short circuit, overload or undervoltage level of the supply voltage, is higher than the threshold value, the autogenerator is turned off.

All main components of the inverter block are made in SMD design.

Monitor does not turn onalthough the power indicator may flicker at times. The reason most often lies in the failure of the power supply board, if it is built into the monitor. If there is no external power supply, then you will have to disassemble the monitor and look for a malfunction. It is very easy to disassemble an LCD monitor in most cases, but always keep in mind the safety precautions when repairing monitors.

Starting to inspect the power supply board, we change all the burnt parts and swollen capacitors found. It is also advisable to inspect the board and soldering under a microscope for possible microcracks. If the monitor is more than 2 years old, then by 50%, there will be microcracks in the soldering in it. Believe it or not, the cheaper the monitor, the worse its assembly, or even a special non-flushing of the active flux.

Image flashes when the monitor is turned on... Most likely the problem is hidden in the power supply. Of course, first you need to check the cables and their reliable mating with the connectors, but if this did not help, then the blinking image tells us that the monitor backlight is constantly jumping off the desired mode. Most often, the reason hides in swollen electrolytic containers, microcracks in the soldering or a faulty TL431 microassembly.

LCD monitor turns off spontaneously or does not turn on immediately... The reason is similar - swollen capacitors, microcracks, faulty TL431. With this problem, a nasty high-frequency squeak of the backlight transformer can also be heard.

No monitor backlight, (the image can be seen under bright outside light). The power supply and inverter board burned out, or the backlight lamps are faulty.If you have a monitor with LED backlighting LED, then there is a darkening of the image in places along the edges of the display. It is better to start repairs by checking the power supply and the inverter board.

Vertical stripes on the monitor screen... This is a very unpleasant malfunction, because the matrix (screen) is 99% unusable due to a broken contact of the signal loop with the LCD display, and finding a new loop is very problematic

There is no picture, but the backlight is working... That is, we see a solid white, gray or blue screen. First, you need to check the cables and try to connect the monitor to another system unit or video card. Also check if it is possible to bring up the monitor menu on the screen. If nothing has changed, we begin to check the power supply board. Or rather, the presence of voltages with a nominal value of 5, 3.3 and 2.5 volts. If they are present and correspond to the nominal value, then we carefully examine the board of the video signal processing unit. This module has a microcontroller, it is necessary to check if power is supplied to it. If everything is fine, then we check all monitor cables. Their contacts must be free of carbon deposits or discoloration. If you find something, wipe it off with alcohol. You should also check the loop and the board with control buttons. If none of the above has helped, then the firmware may have flown or the microcontroller has failed. This often happens from power surges in the 220 V network or from natural aging of radio components.

The monitor does not respond to pressing control buttons... We remove the frame or back cover and take out the board with buttons. Most often we see a crack in the board or in the soldering. Sometimes there are faulty buttons or the loop itself. Having found a crack in the board, the place must be cleaned and well soldered.

Low monitor brightness. This happens due to aging of the backlight lamps. In addition, a decrease in the parameters of the inverter is possible. It is treated by replacing the backlight lamps and very rarely by repairing the inverter.

Noise, moire and jitter in the monitor... This is very common due to a bad interface cable. If replacing does not work, then some power interference is likely entering the imaging circuit. You can get rid of them by installing additional power filtering capacities on the signal board.

It so happened that once the screen of the Samsung 740N monitor, which has faithfully served me for almost 11 years, suddenly went out almost immediately after turning it on. Other attempts to enable and disable were unsuccessful, because according to the signals from the sound card, the operating system was booted successfully, it became clear that the problem lies in the monitor. Of course, a radio amateur cannot so easily throw out an old electronic device without trying to fix it, well, or raskurochit broken device for parts, then how it goes.

A quick search [1-6] showed that the most common problem with monitors of this type is the failure of electrolytic capacitors in the power supply. In general, such a repair is within the power of even the most novice radio amateur, so you can get by with the purchase of several radio components at the place of purchase of the monitor, which is a couple of orders of magnitude cheaper, the cost of your own time, of course, is not taken into account. But in order to repair something, you first need to get inside the monitor, do it carefully, without marks on the case, perhaps the most difficult part of the repair. First you need to put the monitor face down, so that the surface of the screen would not be damaged, after that you should unscrew the screws holding the stand.

The back cover of the monitor is held by latches located around the perimeter of the monitor case. To open the latches, insert a strong thin object, such as an unnecessary plastic card or a metal ruler, into the gap between the screen frame and the back cover, and then sequentially and slowly unscrew all the latches holding the cover. Under the back cover, such a spectacle appears before us.In the next photo, the cover that covers the power connectors of the backlight lamps is also removed.

It should be noted that the metal casing visible in the photo above, to which most of the structural elements are attached, is fixed in the desired position with the help of the back cover and is not fixed to anything else. Before further disassembling the monitor, carefully document the wiring of all internal connectors. True, a real chance to confuse the connectors exists only for the power connectors for the backlight lamps.

Just in case, we fix the position of the remaining connectors.

Now, from the actual screen, you can remove the casing with the printed circuit boards fixed in it.

Then we remove the power supply board.

As expected, three failed electrolytic capacitors are visible on the board.

Finally, we disconnect the power supply board and remove the protective film that covers the board from the side of the printed conductors, this film is held on 3 plastic clips.

In addition to the obviously failed capacitors, a number of sources reviewed recommend replacing the C107 capacitor for preventive purposes.

This radio part has been replaced with a 47 μF x 250 V capacitor.

Just as the reviewed sources indicated, the fuse F301 breaks down along with the capacitors. In the photo, this is a green radio component, which is visible next to the swollen electrolytic capacitors.

We remove suspicious and clearly damaged radio components from the board. The main culprits are that the author of these lines was left without a computer on May 9, 2017.

In place of the failed radio components, we install similar capacitors. Instead of a 3 A fuse, a 3.15 A fuse with solder leads is installed.

After assembly, the monitor's performance was fully restored, after three weeks of intensive use, no deviations were noticed in the work. The author of the material is Denev.

Until 2004-2005, CRT monitors and televisions, or, in other words, having a kinescope in their composition were distributed in mass use. They are also, like televisions, called monitors and CRT (cathode ray tube) type monitors. But progress does not stand still, and at one time LCD TVs were released, which included an LCD (liquid crystal) matrix. Such a matrix must be well illuminated by 4 CCFL lamps located on both sides, top and bottom.

This applies to 17 - 19 inch monitors and TVs. Larger TVs and monitors may have six or more lamps. Such lamps in appearance resemble ordinary fluorescent lamps, but, in contrast, are much smaller in size. Of the differences, such lamps will not have 4 contacts, as in fluorescent lamps, but only two, and their operation requires a high voltage - over a kilovolt.

Monitor backlight connector

So, after 5-7 years of operation, these lamps often become unusable, malfunctions are typical for ordinary fluorescent lamps. Here is some additional information. First, reddish tints appear in the image, a slow start, in order for the lamp to light up, it needs to blink several times. In severe cases, the lamp does not light up at all. The question may arise: well, one lamp has gone out, they are standing above and below the matrix, usually two pieces installed parallel to each other, let only three of them burn and the image will only be dimmer. But not everything is so simple.

The fact is that when one of the lamps goes out, the protection on the PWM controller of the inverter will work, and the backlight, and most often the entire monitor, will be turned off. Therefore, when repairing LCD monitors and televisions, if there is a suspicion of an inverter or lamps, it is necessary to check each of the lamps with a test inverter. I purchased such a test inverter on Aliexpress as in the photo below:

Test inverter with Ali express

This test inverter has a connector for connecting an external power supply, wires with crocodiles at the output, and connectors for connecting plugs, monitor lamps. There is information on the network that such lamps can be checked for operability, using an electronic ballast from energy-saving lamps, with a burned-out lamp spiral, but having working electronics.

Electronic ballast from an energy-saving lamp

What if, using a test inverter or electronic ballast from an energy-saving lamp, you found out that one of the lamps has become unusable and does not light up at all when connected? You can, of course, order lamps on Aliexpress, by the piece, but given that these lamps are very fragile, and knowing the Russian Post, you can easily assume that the lamp will come broken.

Broken Matrix LCD Monitor

You can also remove the lamp from a donor, such as a monitor with a broken matrix. But it is not a fact that such lamps will last a long time, since they have already partially exhausted their resource. But there is another option, a non-standard solution to the problem. You can load one of the outputs from transformers, and there are usually 4 of them, according to the number of lamps on 17 inch monitors, resistive or capacitive load.

Power supply and monitor inverter board

If everything is clear with a resistive one, it can be an ordinary powerful resistor, or several connected in series or in parallel, in order to gain the required rating and power. But this solution has a significant drawback - resistors will generate heat when the monitor is operating, and given that it is usually hot inside the monitor case, additional heating may not please electrolytic capacitors, which, as you know, do not like prolonged overheating and swell.

Swollen capacitors monitor power supply

As a result, if it were, for example, a 400-volt network electrolytic capacitor, that same big barrel known to everyone from the photo, we could get a burnt-out mosfet or a PWM controller microcircuit with a built-in power element. So, there is another way out: to extinguish the required power using a capacitive load, a capacitor 27 - 68 PicoFarad and an operating voltage of 3 Kilovolts.

This solution has some advantages: there is no need to place bulky heating resistors in the case, but it is enough to solder this small capacitor to the contacts of the connector to which the lamp is connected. When choosing the rating of the capacitor, be careful not to solder any ratings, but strictly according to the list at the end of the article, in accordance with the diagonal of your monitor.

We solder the capacitor instead of the backlight lamp

If you solder a smaller capacitor, your monitor will turn off as the inverter will still go into protection due to the fact that the load is small. If you solder a larger capacitor, the inverter will work with overload, which will negatively affect the service life of the mosfets at the output from the PWM controller.

If the mosfets are broken, the backlight, and possibly the entire monitor, will also not be able to turn on, since the inverter will go into protection. One of the signs of overloading the inverter will be extraneous sounds coming from the inverter board, such as hiss. But with the VGA cable disconnected, sometimes a slight hiss coming from the inverter board is normal.

Selection of capacitor ratings for the monitor

The photo above shows imported capacitors, there are also their domestic counterparts, which usually have a slightly larger size. I once soldered ours, domestic at 6 KiloVolts - it all worked. If your radio store does not have capacitors for the required operating voltage, but there are, for example, 2 KiloVolts, you can solder 2 capacitors 2 times larger in series, while their total operating voltage will increase and allow them to be used for our purposes.

Likewise, if you have capacitors 2 times smaller, 3 Kilovolts, but not at the required rating, you can solder them in parallel. Everyone knows that series and parallel connection of capacitors are considered according to the inverse formula of series and parallel connection of resistors.

Parallel connection of capacitors

In other words, when capacitors are connected in parallel, we use the formula for the series connection of resistors or their capacitance is simply added, with a series connection, the total capacitance is calculated using a formula similar to the parallel connection of resistors. Both formulas can be seen in the figure.

DIY monitor repair

Many monitors were already directed in a similar way, the backlight brightness dropped slightly, due to the fact that the second lamp on top or bottom of the monitor or TV matrix still functions and gives, albeit less, but sufficient illumination so that the image remains quite bright.

Condensers in the online store

Such a solution for home use may well suit a novice radio amateur, as a way out of this situation, if the alternative is to repair in a service costing one and a half to two thousand, or buy a new monitor. These capacitors cost only 5-15 rubles per piece in radio stores in your city, and any person who knows how to hold a soldering iron in their hands can perform such repairs. Successful repairs to everyone! Especially for Radioskot.ru - AKV.

In the previous articles devoted to the repair of computer power supplies, we learned how to find and fix simple breakdowns. Let's take a simple look at how switching power supplies differ from conventional transformer ones? The switching power supply unit is capable of delivering significant power to the load with a rather modest size. For this reason, almost all modern technology, with the exception of audio technology (it’s taboo there), is powered by impulses.

Oh yeah, what's all this about? The fact is that a switching power supply is installed in the monitors. And the knowledge that we gained from previous articles on the repair of power supplies is fully applicable to the repair of power supplies for monitors. The difference is purely in the dimensions and layout of radio components.

The giblets of a power supply for a computer look something like this:

And the power supply for the monitor is something like this:

But there is also a significant difference. In power supplies for monitors with LCD backlight, you can see the high-voltage part. He's an inverter. His presence is indicated by inscriptions such as "High Voltage" and terminals for connecting lamps. Please note that the voltage supplied to the lamps is over 1000 volts! Therefore, it is better not to touch and even more so not to lick this part when you turn on the Monica in the network.

By the way, what is the difference between LCD backlit monitors and LED backlit monitors? In LCD monitors, we use fluorescent lamps for backlighting. This is almost the same as fluorescent lamps, just reduced several times.

These lamps are located at the top and bottom of the display and illuminate the image.

If you turn them off, the image will be so dim that you think the display is off altogether. Only a close inspection under lighting can show that there is still an image on the display. This trick will be useful to us to determine lamp malfunctions.

LED monitors use LEDs for backlighting, which are located either on the sides of the display, or behind it.

Now all manufacturers of monitors and TVs have switched to LED backlighting, since it reduces energy consumption by almost half and is much more durable than LCD.

A modern LCD monitor consists of only two boards: a scaler and a power supply

Scaler Is a monitor control board. His brain. Here the monik converts the digital signal into colors on the display, and also contains various settings.It contains the processor, flash-memory, where the monitor's firmware is written, and EEPROM-memory, in which the current settings are saved.

Power Supply, in fact, provides power to the monitor circuit. As I said, it can contain an inverter for monics with LCD backlight. In monitors with LED backlight, there is no inverter.

So, what are the most common monitor breakdowns and what causes them? These are, of course, electrolytic capacitors in the power supply filter.

This is one of the most common LCD monitor breakdowns. Conder can be re-soldered easily and easily. Sometimes the boards do not have a standard capacitor rating, for example 680 or 820 microfarad x 25 volts. If you are faced with swollen capacitors of this denomination and they were not in your radio store, do not rush to go around all the radio stores in your city in search of the exact same denomination. This is exactly the case when "a lot is not harmful." Any electronics engineer will tell you this. Feel free to put 1000 microfarads x 25 volts and everything will work fine. Even more is possible.

Due to the fact that the power supply emits heat during operation, which adversely affects the life of the capacitors, be sure to put capacitors with the designation "105C" on the case. Also, after re-soldering the capacitors, it does not hurt to check the secondary circuit fuse, which is often a simple SMD resistor with zero resistance, frame size 0805, located on the back of the board from the routing side.

And one more nuance, at the output of the power supply, in front of the power connector itself going to the scaler, an SMD zener diode is often placed

If the voltage on it exceeds the nominal, it goes into a short circuit and thereby disconnects our monitor through the protection circuits. You can replace it with any one that is suitable for the voltage rating. Can even be used with pins

After everything is done and repaired, we check with a multimeter the voltage at the power connector, which goes to the scaler. All tensions are signed there. Make sure they match the readings of the multimeter

Problems in the high-voltage part of the power supply (inverter).

If possible, then first of all, always look for the schematics of the device being repaired. Let's take a look at the high voltage part of one of the monitors.

If you see that the monitor power supply fuse is blown, it means that the resistance between the power wires of the monitor cord (input resistance) has become very low at some point (short circuit). Somewhere around 50 ohms or less, which in turn, according to Ohm's law, caused an increase in the current in the circuit. Because of the high current, the fuse wires burned out.

If the fuse is in a metal-glass case, we can insert absolutely any fuse into the mount and ring the resistance between the pins of the plug with a multimeter in 200 Ohm Ohmmeter mode. If our resistance is zero and up to 50 ohms, which is most often the case, then we are looking for a broken radio element that rings to zero or to ground.

Insert the fuse, switch the multimeter to 200 ohms and connect it to the power plug. We make sure that the resistance is very small. Further, we are in no hurry to remove the fuse. So let's see, according to the diagram, which radio components can be short-circuited with us. In the photo, the parts that need to be checked in case of a short circuit in the high-voltage part are highlighted in colored frames

All these procedures for measuring resistance are done in order to call the listed parts one by one. That is, we solder and again measure the resistance through the plug. As soon as we get a high resistance at the input of the plug, replacing the defective radio element, then we can safely plug the plug into the socket.

Monitor backlight disappears

The problem is this: our monitor turns on, it works for 5-10 seconds and goes out. This indicates that one of the display backlight lamps has become unusable. Before that, part of the screen may blink a little.In this case, the inverter will go into protection, which will manifest itself in the automatic shutdown of the monitor backlight.

In order for us to check the lamps and exclude the defective one, we buy a high-voltage capacitor 27 picofarads x 3 kilovolts for 17 "monitors, 47 pF for 19" monitors and 68 pF for 22 "monitors from a radio store.

This capacitor must be soldered to the pins of the connector to which the backlight is connected. The lamp itself, of course, must be turned off. By connecting the capacitor in turn to each connector, we ensure that the inverter stops going into protection.

The monitor will work, although it will be a little dim. This is useful as a temporary solution while the lamp is expected to be delivered, for example from China, or as a permanent solution if it is impossible for one reason or another to replace the backlight.

Of course, rarely does anyone do that. The very trick is to turn off the protection on the PWM chip itself))). To do this, google "remove the protection of the inverter xxxxxxx" Instead of "xxxxxx" we put the brand of our PWM microcircuit. Somehow I turned off the protection on a monitor with a TL494 PWM microcircuit according to the diagram below by soldering a 10 Kiloohm resistor. Monique has been working for the second year now. No complaints).

Today I want to share with you the experience of repairing a monitor with my own hands. I repaired my old one LG Flatron 1730s... Like this:

This is a 17 "LCD monitor. I must say right away that when there is no image on the monitor, we (at work) immediately refer such copies to our electronics engineer and he deals with them, but there was an opportunity to practice 🙂

To begin with, let's understand the terminology a little: earlier, CRT monitors (CRT - Cathode Ray Tube) were in use. As the name implies, they are based on a cathode ray tube, but this is a literal translation, it is technically correct to talk about a cathode ray tube (CRT).

Here is a disassembled sample of such a "dinosaur":

Nowadays LCD type of monitors (Liquid Crystal Display - display on the basis of liquid crystals) or simply LCD is in vogue. These designs are often referred to as TFT monitors.

Although, again, if we speak correctly, then it should be like this: LCD TFT (Thin Film Transistor - screens based on thin-film transistors). TFT is simply the most widespread variety, more precisely, LCD (liquid crystal) display technology.

So, before we start repairing the monitor ourselves, let's consider what “symptoms” did our “patient” have? In short: there is no image on the screen... But if you look a little more closely, then various interesting details began to emerge! 🙂 When turned on, the monitor showed an image for a split second, which immediately disappeared. At the same time (judging by the sounds), the system unit of the computer itself worked properly and the operating system was loaded successfully.

After waiting for a while (sometimes 10-15 minutes), I found that the image appeared spontaneously. Repeating the experiment several times, I was convinced of this. Sometimes for this, however, you had to turn off and turn on the monitor with the "power" button on the front panel. After resuming the picture, everything worked without interruptions until the computer was turned off. The next day, history and the whole procedure were repeated again.

Moreover, I noticed an interesting feature: when the room was warm enough (the season is no longer summer) and the batteries were heated fairly, the idle time of the monitor without an image was reduced by five minutes. There was a feeling that it warms up, reaching the desired temperature regime and then works without problems.

This became especially noticeable after one day the parents (the monitor was with them) turned off the heating and the room became quite fresh. In such conditions, the image on the monitor was absent for about 20-25 minutes, and only then, when it got hot enough, did it appear.

According to my observations, the monitor behaved exactly like a computer with certain problems of the motherboard (capacitors that have lost capacity). If it is enough to warm up such a board (let it run or direct the heater towards it) it normally “starts up” and, quite often, works without interruptions until the computer is turned off. Naturally, this is - until a certain moment!

But at the early stage of diagnostics (before the opening of the patient's case), it is highly desirable for us to make the most complete picture of what is happening. According to it, we can roughly navigate in which node or element the problem is? In my case, after analyzing all of the above, I thought about the capacitors located in the power circuit of my monitor: turn on - there is no image, the capacitors are warming up - it appears.

Well, it's time to test this assumption!

Let's disassemble! First, using a screwdriver, unscrew the screw that secures the bottom of the stand:

Then, - remove the corresponding screws and remove the base of the stand attachment:

Next, using a flat-tipped screwdriver, we pry the front panel of our monitor and in the direction indicated by the arrow, we begin to carefully separate it.

Slowly, we move along the perimeter of the entire matrix, gradually removing the plastic latches holding the front panel from their seats with a screwdriver.

After we disassembled the monitor (separated its front and rear parts), we see the following picture:

If the “insides” of the monitor are attached to the back panel with adhesive tape, peel it off and remove the matrix itself with the power supply and control board.

The back plastic panel remains on the table.

Everything else in the disassembled monitor looks like this:

This is how the “filling” looks in the palm of my hand:

Let's show a close-up of the panel of settings buttons that are displayed for the user.

Now, we need to disconnect the contacts connecting the cathode backlight lamps located in the monitor matrix with the inverter circuit responsible for their ignition. To do this, we remove the aluminum protective cover and see the connectors under it:

We do the same on the opposite side of the monitor's protective casing:

Disconnect the connectors from the monitor inverter to the lamps. Who cares, the cathode lamps themselves look like this:

They are covered on one side with a metal casing and are located in it in pairs. The inverter “lights up” the lamps and adjusts the intensity of their light (controls the brightness of the screen). Now, instead of lamps, LED backlights are increasingly used.

Advice: if you find that on the monitor suddenly the image is gone, take a closer look (if necessary, illuminate the screen with a flashlight). Perhaps you will notice a faint (faint) image? There are two options here: either one of the backlight lamps is out of order (in this case, the inverter simply goes “in defense” and does not supply power to them), remaining fully operational. The second option: we are dealing with a breakdown of the inverter circuit itself, which can either be repaired or replaced (in laptops, as a rule, they resort to the second option).

By the way, the laptop inverter is located, as a rule, under the front outer frame of the screen matrix (in the middle and bottom of it).

But we got distracted, we continue to repair the monitor (more precisely, for now, chuck it) 🙂 So, having removed all the connecting cables and elements, we disassemble the monitor further. We open it like a shell.

Inside we see another cable connecting, protected by another casing, the matrix and monitor backlight lamps with the control board. Peel off the scotch tape up to half and see under it a flat connector with a data cable in it. We carefully remove it.

We put the matrix separately (we will not be interested in it in this repair).

This is how it looks from the back:

Taking this opportunity, I want to show you the disassembled monitor matrix (recently they tried to repair it at work). But after analysis, it became clear that it would not be possible to fix it: some of the liquid crystals on the matrix itself burned out.

In any case, I shouldn't have seen my fingers behind the surface so clearly! 🙂

The die is secured in a frame that holds and holds all of its parts together using snug plastic snaps. In order to open them, you will have to work thoroughly with a flat screwdriver.

But with the type of do-it-yourself monitor repair that we are doing now, we will be interested in another part of the design: the control board with the processor, and even more so, the power supply of our monitor. Both of them are shown in the photo below: (photo - clickable)

So, in the photo above, on the left, we have a processor board, and on the right, a power board combined with an inverter circuit. A processor board is often referred to as a scaler board (or circuit).

The scaler circuit processes the signals coming from the PC. In fact, a scaler is a multifunctional microcircuit, which includes:

• microprocessor
• a receiver (receiver) that receives a signal and converts it into the desired type of data, transmitted via digital interfaces for connecting a PC
• an analog-to-digital converter (ADC) that converts the input analog R / G / B signals and controls the resolution of the monitor

In fact, a scaler is a microprocessor optimized for the task of image processing.

If the monitor has a frame buffer (random access memory), then work with it is also carried out through the scaler. For this, many scalers have an interface for working with dynamic memory.

But we - again distracted from the repair! Let's continue! 🙂 Let's take a close look at the monitor power combo board. We will see such an interesting picture there:

As we assumed at the very beginning, remember? We see three swollen capacitors requiring replacement. How to do it correctly is described here in this article of our site, we will not be distracted once again.

As you can see, one of the elements (capacitors) swelled not only from above, but also from below, and some of the electrolyte flowed out of it:

To replace and effectively repair the monitor, we will need to completely remove the power board from the casing. We unscrew the fastening screws, take out the power cable from the connector and take the board in our hands.

Here is a photo of her back:

I want to say right away that quite often the power board is combined with the inverter circuit on one PCB (printed circuit board). In this case, we can talk about a combination board, represented by the power supply of the monitor (Power Supply) and the inverter of the backlight (Back Light Inverter).

In my case, this is exactly the case! We see that in the photo above, the lower part of the board (separated by a red line) is, in fact, the inverter circuit of our monitor. It happens that the inverter is represented by a separate PCB, then there are three separate boards in the monitor.

The power supply (the upper part of our PCB) is based on the FAN7601 PWM controller microcircuit and the SSS7N60B field-effect transistor, and the inverter (its lower part) is based on the OZL68GN microcircuit and two FDS8958A transistor assemblies.

Now we can safely start repairing (replacing capacitors). We can do this by conveniently placing the structure on the table.

This is how the area of ​​interest to us will look after removing faulty elements from it.

Let's take a close look at what nominal capacitance and voltage do we need to replace the elements soldered from the board?

We see that this is an element with a rating of 680 microfarads (mF) and a maximum voltage of 25 volts (V). In more detail about these concepts, as well as about such an important thing as maintaining the correct polarity when soldering, we talked with you in this article. So, let's not dwell on this again.

Let's just say that we have failed two 680 mF capacitors with a voltage of 25V and one at 400 mF / 25V.Since our elements are connected in parallel to the electrical circuit, we can safely use two 1000 mF capacitors instead of three capacitors with a total capacity (680 + 680 + 440 = 1800 microfarads), which will add up to the same (even greater) capacitance.

The capacitors removed from our monitor board look like this:

We continue to repair the monitor with our own hands, and now it is time to solder the new capacitors in place of the removed ones.

Since the elements are really new, they have long “legs”. After soldering in place, just carefully cut off their excess with side cutters.

As a result, we got it like this (for the sake of order, for two 1000 microfarad capacitors, I put an additional 330 mF element on the board).

Now, we carefully and carefully reassemble the monitor: fasten all the screws, connect all cables and connectors in the same way, and, as a result, we can proceed with an intermediate test run of our half-assembled structure!

Advice: there is no point in putting the entire monitor back together, because if something goes wrong, we will have to disassemble everything from the very beginning.

As you can see, the frame, signaling the absence of a connected data cable, appeared immediately. This, in this case, is a sure sign that the repair of the monitor with our own hands was successful with us! 🙂 Previously, until the malfunction was corrected, there was no image at all until it warmed up.

Mentally shaking hands with ourselves, we assemble the monitor to its original state and (for testing) we connect it with a second display to the laptop. We turn on the laptop and see that the image immediately "went" to both sources.

Q.E.D! We just repaired our monitor ourselves!

note: To find out what other types of TFT monitor malfunctions there are, follow this link.

That's all for today. I hope this article was helpful to you? See you next on the pages of our site 🙂