DIY ldzhi monitor repair power supply

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 do not rush 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 outlet.

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 the monitor with the 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, it was necessary 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 a 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 diagnosis (before opening 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 is the problem? In my case, after analyzing all of the above, I thought about the capacitors located in the power supply circuit of my monitor: we 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, chick 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 the processor board, and on the right, the power board combined with the 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 form 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 🙂

Here are the TOP 10 most common LCD monitor malfunctions that I felt the hard way. The fault rating was compiled according to the author's personal opinion, based on the experience of working in the service center. You can take this as a universal repair manual for almost any LCD monitor from Samsung, LG, BENQ, HP, Acer and others. Here we go.

I divided the malfunctions of LCD monitors into 10 points, but this does not mean that there are only 10 of them - there are many more, including combined and floating ones. Many of the breakdowns of LCD monitors can be repaired by hand or at home.

in general, although the power indicator may be blinking. At the same time, twitching the cable, dancing with a tambourine and other pranks do not help. Tapping the monitor with a nervous hand usually doesn't work either, so don't even try. The reason for such a malfunction of LCD monitors is most often the failure of the power supply board, if it is built into the monitor.

Recently, monitors with an external power source have become fashionable. This is good because the user can simply change the power supply in the event of a breakdown. If there is no external power source, then you will have to disassemble the monitor and look for a malfunction on the board. In most cases, it is not difficult to disassemble an LCD monitor, but you need to remember about safety.

Before fixing the poor fellow, let him stand for 10 minutes, unplugged. During this time, the high-voltage capacitor will have time to discharge. ATTENTION! DANGEROUS TO LIFE if the diode bridge and the PWM transistor burn out! In this case, the high voltage capacitor will not discharge in an acceptable time.

Therefore, EVERYONE before repairing to check the voltage on it! If a dangerous voltage remains, then the capacitor must be manually discharged through an insulated resistor of about 10 kOhm for 10 seconds. If you suddenly decide to close the terminals with a screwdriver, then keep your eyes away from sparks!

Next, we proceed to inspect the monitor power supply board and change all burned-out parts - these are usually swollen capacitors, blown fuses, transistors and other elements. It is also MANDATORY to solder the board or at least inspect the soldering under a microscope for microcracks.

From my own experience I will say - if the monitor is more than 2 years old - then 90% that there will be microcracks in the soldering, especially for LG, BenQ, Acer and Samsung monitors. The cheaper the monitor, the worse it is made at the factory. Up to the point that the active flux is not washed out - which leads to the failure of the monitor after a year or two. Yes, yes, just when the guarantee ends.

when the monitor is turned on. This miracle directly indicates to us a malfunction of the power supply.

Of course, the first step is to check the power and signal cables - they must be securely fastened in the connectors. A blinking image on the monitor tells us that the monitor backlight voltage source is constantly jumping off the operating mode.

The most common reason for this is swollen electrolytic capacitors, microcracks in the solder and a faulty TL431 microcircuit.Swollen capacitors most often cost 820 uF 16 V, they can be replaced with a larger capacity and a higher voltage, for example, the cheapest and most reliable ones are Rubycon 1000 uF 25 V capacitors and Nippon 1500 uF 10 V capacitors. 105 degrees) Nichicon 2200 uF 25 V. Everything else will not last long.

after the time has elapsed or does not turn on immediately. In this case, again, three frequent LCD monitors malfunctions in order of frequency of occurrence - swollen electrolytes, microcracks in the board, faulty TL431 microcircuit.

With this fault, a high-frequency squeak of the backlight transformer can also be heard. It usually operates at frequencies between 30 and 150 kHz. If the mode of its operation is violated, oscillations can occur in the audible frequency range.

but the image is viewed under bright light. This immediately tells us about a malfunction of LCD monitors in terms of the backlight. In terms of the frequency of occurrence, it could be put in third place, but it has already been taken there.

Option two - either the power supply and inverter board burned out, or the backlight lamps are faulty. The latter reason is not common in modern monitors with LED backlighting. If the LEDs are backlit and fail, then only in groups.

In this case, there may be a darkening of the image in places at the edges of the monitor. It is better to start repairs with diagnostics of the power supply and inverter. An inverter is the part of the board that is responsible for the formation of a high-voltage voltage of the order of 1000 volts to power the lamps, so in no case should you try to repair the monitor under voltage. You can read about repairing the Samsung monitor power supply in my blog.

Most monitors are similar in design, so there shouldn't be any problems. At one time, monitors simply rained down with a breakdown in contact near the tip of the backlight. This is treated by the most careful disassembly of the matrix to get to the end of the lamp and solder the high voltage wires.

If the backlight itself burns out, I would suggest replacing it with the LED backlight bar that usually comes with your inverter. If you still have questions - write to me by mail or in the comments.

These are the nastiest LCD monitor malfunctions in the life of any computer technician and user, because they tell us that it's time to buy a new LCD monitor.

Why buy new? Because your pet's matrix is ​​90% unusable. Vertical stripes appear when the contact of the signal loop with the contacts of the matrix electrodes is broken.

This can only be cured by careful application of anisotropic adhesive tape. Without this anisotropic glue, I had a bad experience repairing a Samsung LCD TV with vertical stripes. You can also read how the Chinese repair such strips on their machines.

An easier way out of this unpleasant situation can be found if your brother-in-law friend has the same monitor lying around, but with faulty electronics. It will not be difficult to blind from two monitors of similar series and the same diagonal.

Sometimes even a power supply unit from a monitor with a larger diagonal can be adapted for a monitor with a smaller diagonal, but such experiments are risky and I do not recommend starting a fire at home. Here in someone else's villa - that's another matter ...

Their presence means that the day before, you or your relatives had a fight with the monitor because of something outrageous.

Unfortunately, household LCD monitors do not provide shockproof coatings and anyone can offend the weak. Yes, any decent poke with a sharp or blunt object into the LCD monitor matrix will make you regret it.

Even if there is a small trace or even one broken pixel, over time, the spot will begin to grow under the influence of temperature and voltage applied to the liquid crystals. Unfortunately, it will not work to restore the dead pixels of the monitor.

That is, there is a white or gray screen on the face.First, you should check the cables and try connecting the monitor to a different video source. Also check if the monitor menu is displayed on the screen.

If everything remains the same, we look closely at the power supply board. In the power supply unit of the LCD monitor, voltages of 24, 12, 5, 3.3 and 2.5 volts are usually formed. It is necessary to check with a voltmeter if everything is in order with them.

If everything is in order, then we carefully look at the video signal processing board - it is usually smaller than the power supply board. It has a microcontroller and auxiliary elements. It is necessary to check whether food comes to them. With one probe, touch the contact of the common wire (usually along the contour of the board), and with the other, go over the terminals of the microcircuits. Usually food is somewhere in the corner.

If everything is in order in the power supply, but there is no oscilloscope, then we check all the monitor loops. There should be no carbon deposits or darkening on their contacts. If you find something, clean it with isopropyl alcohol. In extreme cases, you can clean it with a needle or scalpel. Also check the ribbon cable and the board with the monitor control buttons.

If all else fails, then perhaps you are faced with a case of a failed firmware or a failure of the microcontroller. This usually happens from surges in the 220 V network or simply from aging of the elements. Usually, in such cases, you have to study special forums, but it's easier to start up for spare parts, especially if you have a familiar karate fighter fighting against objectionable LCD monitors.

This case is easily treated - you need to remove the frame or the back cover of the monitor and pull out the board with buttons. Most often, there you will see a crack in the board or in the solder.

Sometimes there are faulty buttons or a loop. A crack in the board violates the integrity of the conductors, so they need to be cleaned and soldered, and the board must be glued to strengthen the structure.

This is due to aging of the backlight lamps. According to my data, LED backlighting does not suffer from this. Deterioration of the parameters of the inverter is also possible due to aging of the constituent components.

This is often due to a bad VGA cable without an EMI suppressor - a ferrite ring. If replacing the cable does not work, then power supply interference may have entered the imaging circuits.

Usually they get rid of them schematically by using filtering capacities for power supply on the signal board. Try to replace them and write to me about the result.

This completes my wonderful rating of the TOP 10 most common LCD monitor malfunctions. Most of the breakdown data is collected from repairs of popular monitors such as Samsung, LG, BENQ, Acer, ViewSonic and Hewlett-Packard.

This rating, it seems to me, is also true for LCD TVs and laptops. What is your situation on the LCD monitor repair front? Write on the forum and in the comments.

The most common questions when disassembling LCD monitors and TVs - how to remove the frame? How do I release the latches? How to remove the plastic from the case? etc.

One of the wizards made a nice animation explaining how to disengage the latches from the chassis, so I'll leave it here - it will come in handy.

To view animation - click on the image.

Recently, monitor manufacturers are increasingly completing new monitors with external power supplies in a plastic case... I must say that this makes it easier to troubleshoot LCD monitors by replacing the power supply. But it complicates the operating mode and the repair of the power supply itself - they often overheat.

I showed how to disassemble such a body in the video below. The method is not the best, but it is fast and can be done with improvised means.

So tell me that you are too lazy to wait half a month from China for a detail.))))

Wasn't it easier to just solder that burned-out part?

not always a problem in such a detail. And if a transformer or a power capacitor is screwed up, go find it, only from donors if you are a pc master. Stumbled upon this vidos and made conclusions for myself

“This may sound like complete nonsense. "

So this is complete nonsense)))

A microcircuit of the order of fifty dollars is worth (and you don't need to shit about what was taken out of production) and how much is the power supply unit from the laptop and the 5V stabilizer board (which you still need to manage to find)

well, the goal is achieved, everything works

Useful video. I did not know about this method. Will there be more similar videos?

In fact, in this way you can repair any power supply unit, stupidly discard the old one and put another one

From experience, even if the shimka is not released, there are probably analogues (I found it in 99% of cases), even with a different pinout, but with similar parameters. Further, with the help of the dip8 pads (or whatever the case is) and the wiring, magic is performed

I want to learn this science of electronics engineer, advise literature?

There were 3 swollen Conder, the replacement did not help, Monica is probably 8 years old, of course he did not poke a tester, because at that time was absent. The only question is how to start the power supply unit without load, it is done so through the ass that everything hangs and one is terribly inconvenient. Monique Proview sp716kp. That's what I asked, maybe they brought with a similar diagnosis.

And if you are a handshake and do not even know how to solder, then feel free to buy a new monique 🙁

And my old LG 17 ″ after turning on does not show anything, but only chirps with the power supply (after half an hour it still turns on), in which direction to dig?

The method is certainly hardcore, but still effective.

This is when our descendants will sit in the ruins of civilization, waiting out the nuclear winter, and all they will have are things brought from short sorties to the surface, this method will be very relevant. And now it's just interesting))

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 necessary

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, which are 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 its 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 changes from the brightness voltage and the threshold voltage level. 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 not have any traces of carbon deposits or darkening. 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.