Do-it-yourself benq w2108 monitor repair

Fault: the monitor does not turn on and the power indicator blinks... The malfunction is typical and immediately hints to us about problems in the power supply, so we proceed to disassembly. To do this, unscrew all the screws on the back of the monitor, including those disguised under the caps. The latter are removed easily enough if you pry them. We take out the stand from the mount and unscrew another screw under it.

We pry the case around the perimeter, disengaging the latches. Sometimes you have to use physical force on especially tight latches, but remember one rule - where the plastic goes better, the latch opens there. The power supply and signal processing board are located under the back cover. Unscrew the DVI and D-Sub (VGA) connectors with narrow-nose pliers. Disconnect the keypad connector and raise the metal screen.

On the left is the power supply board, on the right is the signal board. The swollen capacitors are clearly visible on the power supply board (marked in red). Disconnect the lamp connectors and unscrew the power supply board. The yellow condenser is not swollen, but it is close to the radiator, therefore, for prevention, I also recommend replacing it.

It is quite common for electrolytic capacitors to swell when located close to radiators and heating components. The electrolyte in them evaporates under the influence of temperature. As a result, the dielectric gasket dries out and overheating of the container with swelling is guaranteed. After replacing all the containers, the monitor turned on.

Benq E2200HDA on ET0019NA chassis.

Just does not turn on, the indication also does not work:

With 99% of these symptoms, you can safely look at the power supply, when dialing, I found the D803 diode short-circuiting, power is supplied to the PO168 through it, after removing the diode, it was found to be fully operational. The dialing of the seventh pin of the microcircuit relative to the case showed its closure. Replacing the microassembly with a similar one (FAN6751), the monitor immediately started working.

Benq FP71E monitor on Q7C4 chassis

When the monitor was turned on, the backlight appeared and immediately went out... It is immediately clear that the problems in the inverter, specifically after getting acquainted with the monitor circuit, Benq determined the reason: transistors Q815 and Q816 2SC5707 are broken, and they burned out due to the electrolytic capacitor C824 0.22mF 160V (see radio amateur advice on how to check the capacitor). A similar problem can occur in the second arm of the Q808 Q809 C826 inverter.

Benq FP71G on Q7T4 chassis (the diagram can be downloaded from the link above).

Display backlight turns off, almost immediately, and sometimes after a few minutes of work. I took the advice of the repairmen and cleaned the backlight wires from the metallized foil (There is a known defect that occurs due to the metallized tape. When the monitor is heated, the tape squeezes the insulation and a breakdown occurs) and washed off the varnish from under the smd capacitors in the inverter circuit, but the problem persisted. Upon further analysis, the circuit revealed a faulty electrolytic capacitor C826. After replacing it, the backlight stopped turning off.

White screen on the monitor screen... On the LCD control board, replace the faulty fuse and dismantle the capacitor C102

Spontaneous switching off of matrix backlight... Bad contact in SN804 connector of the inverter board, blue wire. Take out, squeeze the petals and put back. When a defect occurs, the backlight lamps light up and immediately go out, if you turn off the faulty lamp, the remaining lamp glows longer.

The backlight turns on and off spontaneously.

A defect in the SMD capacitor C841, when dismantled and inspected, it was split from the bottom side. After replacing the monitor backlight worked.

Color distortion. Control panel buttons do not work.

There is a reaction only to the “On-Off” button. If you click on the others, there is no change. The problem is in the EEPROM U4 24C04N.

Monitor does not turn on: The power supply is OK. I tried to replace the EEPROM U4 24C04N, the monitor turned on, but soon froze again. As I found out, the quartz Y1 24.000 was faulty, (How to check the quartz).

Monitor turns off after 5-10 minutes

The power supply has a faulty 3.3V stabilizer IC701 LD1117

White screen... After 15 minutes of work

Defective microcircuit U11 AAT1164 (analogue of max1517). After replacing it with an analog, the microcircuit became very hot, I had to install it on a radiator for prevention, a similar problem often arises in the Benq FP73G monitor on the Q7T5 chassis

The control buttons do not work, everything except the inclusion... The button lock mode is on; to exit it, press and hold the MENU button

No sound... The problem is in the TDA7496 chip, after replacing it, the sound appeared

White screen In these monitors, this failure occurs mainly due to a blown fuse on the AU Optronics M190EG02 board. Usually, in this case, capacitors C11, C12, C13 fail.

The problem is as follows: if you turn off the monitor after 1-2 hours of work, it is more does not turn on, the indicator is off, and if you wait 30 minutes, the monitor turns on again. Replaced capacitor C712.

If the monitor just won't turn on... Lowered supply voltage 3.3V to 2.5V; 5V to 3.3V due to IC601 NCP1200AP40 chip.

The monitor turns off at various intervals. Dark image.

The problem is in the inverter to check the capacitor C822 (in my case it turned out to be split).

The inscription on the monitor Cable not connected

The malfunction turned out to be in the Zener diode D4 (I checked it with a multimeter in the diode test mode, passed it in both directions)

After an hour of work, the control buttons were stuck... The problem turned out to be in the ZD5 in the Exit button circuit.

Does not turn on... Resistor R603 burned out in the power supply, and IC601 NCP1200AP40 microcircuit and IC602 PC123 optocoupler are faulty. (how to check an optocoupler)

Benq FP93GS on Q9T5 chassis

Malfunction - White raster.

Check capacitor C193, transistor Q5 ELM13401CA

BENQ FP557s no response to control buttons

The reason turned out to be in the buttons themselves, namely in autotuning, in this case.

The examination revealed burnt radio components Q743; Q751; Q741; Q753; Q742; Q752; PF751 was replaced with similar or analogs, when turned on, the PF751 fuse was blown again and Q759 broke. Upon further search for the problem, a short circuit was found in the secondary windings of the T753 transformer.

The PF751 fuse and the Q759 2SC5707 transistor are faulty due to the lack of loss of the first leg of the T751 transformer.

Monitor does not turn on... The power supply is faulty, namely the Q601 P7NK80ZFP transistor, the IC601 NCP1200AP40 microcircuit and the breakage of the R615 R22 resistors and the F601 fuse are broken.

Problems in the inverter board: Q808 transistors burned out; Q809 2SC5707 Q805 FQU11P06 fuse PF801 capacitor C826.

It turns off after a short time, the indicator is off, before disconnecting the white matrix.

Problems in the monitor's power supply, because the output has an unstable voltage, 5V each. The IC601 NCP1200AP40 microcircuit and the Q601 transistor turned out to be faulty.

The backlight flashes on and off... In one arm of the inverter, I found burnt 2SD5707 (pos. Numbers Q808 and Q809) and swollen capacitors C801 C707, C708 between them. The yellow fuse PF801 3A has also blown.

I was offered to buy a faulty benq FP91G for 2t.r. , took it on trial so far. Initially, I assumed that there was a problem with the inverter, since the monitor works for 20 seconds and turns off.
So, after the autopsy, as usual, both c5707 were killed and the conduit between them was cracked. But I'm not talking about that, since the inverter circuit has been plowed enough to me, it may make sense to buy a separate inverter in the store, it costs 300-400 rubles. the choice is great. Dear conference, tell me on what basis to buy, and is there any sense of this perversion.

MAIN IMPORTANT replace both conduits between c5707, the whole problem is in them.
During operation, they heat up and are sealed off (forming a microcrack) and then the c5707 also die.
I put the same denomination but without case (type K73-17), NO returns!
There is no need to change the inverter!
Good luck.

Dear moderator, do not correct the title of the topic, as the discussion moves away from the originally asked question.
Thank you.

You can look for 11P06 (I had these when Monique came for repairs) and 17P06 (I installed these because I did not find the first ones). Everything is working.And yes, check out the Q811 and similar on the other shoulder. On my Monica, the backlight also shone right away, the Q811 case was with a hole. Q805 and Q812 replaced without thinking

Zyuyu: two thousand for BENQ in my opinion a bit too much. 1500 max.

Hello friends! Today we'll talk about repairs BenQ Q9T4 LCD Monitor... On his face it is written BenQ FP91G... Malfunction of this monitor - does not turn on, the power indicator flashes... In this case, the defect is determined quickly enough even without disassembly. LCD monitors eventually suffer from dried out capacitors, which disrupts the operation of the switching power supply and leads to a refusal to turn on. We prepare a pack of capacitors and disassemble the monitor. On the back of the monitor we unscrew all the screws, including under the plugs.

We prepare a pack of capacitors and disassemble the monitor. On the back of the monitor we unscrew all the screws, including under the plugs.

The plugs can be removed easily if you pry them with something sharp.

We take out the stand from the mount and unscrew another self-tapping screw under it.

We pry the monitor case along the seam around the perimeter, releasing the latches. Sometimes you have to use force on tight latches, but remember one thing - where the plastic is better served, the latch opens there. Under the back cover we see the power supply screen and the signal processing board.

We unscrew the fasteners of the DVI and D-Sub (VGA) connectors... I usually do this with narrow-nose pliers.

Disconnect the monitor keypad connector and raise the metal screen.

On the left we see the power supply board, on the right - the monitor signal board. Swollen capacitors are found on the power supply board. Disconnect the lamp connectors and unscrew the power supply board.

A condenser is circled in yellow, which has not swollen, but is suspiciously close to the radiator. This capacitor would also be better replaced. For example, it can be replaced with a larger capacity and a higher voltage, for example, the cheapest and most reliable are known - these are capacitors Rubycon 1000 uF 25 V and capacitors Nippon 2200 uF 25 V... There are cheaper of the decent ones (but always by 105 degrees) Samwha 2200 uF 25 V.

Typically, electrolytic capacitors will swell when installed close to radiators and heating elements. The electrolyte in them, under the influence of temperature, begins to actively evaporate through microgaps. As a result, we get the drying out of the dielectric spacer and overheating of the capacitor with swelling.

I advise you to install fresh good capacitors with an operating temperature of 105 degrees Celsius from Sanyo, Samwha, Fujitsu, Teapo, Rubycon, CapXon, Nippon, Jamicon. I ended up with a Jamicon of solid size. I barely got them in, but now I am sure that the monitor will work quietly from 1 to 3 years in office mode.

It is better to solder the power supply board in the area of ​​contacts of massive and heating radioelements, because in some places the factory solder lays down in a thin layer and cracks over time. If you use rosin, then be sure to wash off its remnants with alcohol, otherwise there will be a leak between the contacts. I am using solder oil or BGA soldering gel and I do not wash anything. It lays down in an even translucent layer and evaporates quickly when soldering.

Assemble BenQ Q9T4 monitor upside-down. At this, the repair of the BenQ FP91G LCD monitor can be considered successfully completed.

Happy renovation!
The Solder Master is with you.

PS: Recently, monitor manufacturers are increasingly completing new monitors with external power supplies in a plastic case... 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.

Many viewers of this video criticize this method of disassembly. I will say that it is certainly not ideal and there are many ways to open such power supplies more accurately. However, in the conditions streaming repair, when more than one device needs to be made and defect in a day, this method of opening is quite relevant. Sometimes there are traces of opening, but they are well masked with sandpaper or a file.

In any case, if you find a more interesting and accurate way of opening, please report it in the comments or on the forum - it will be useful to all Masters and Novice Repairmen. Success to everyone!

I was offered to buy a faulty benq FP91G for 2t.r. , took it on trial so far. Initially, I assumed that there was a problem with the inverter, since the monitor works for 20 seconds and turns off.
So, after the autopsy, as usual, both c5707 were killed and the conduit between them was cracked. But I'm not talking about that, since the inverter circuit has been plowed enough to me, it may make sense to buy a separate inverter in the store, it costs 300-400 rubles. the choice is great. Dear conference, tell me on what basis to buy, and is there any sense of this perversion.

MAIN IMPORTANT replace both conduits between c5707, the whole problem is in them.
During operation, they heat up and are sealed off (forming a microcrack) and then the c5707 also die.
I put the same denomination but without case (type K73-17), NO returns!
There is no need to change the inverter!
Good luck.

Dear moderator, do not correct the title of the topic, as the discussion moves away from the originally asked question.
Thank you.

You can look for 11P06 (I had these when Monique came for repairs) and 17P06 (I installed these because I did not find the first ones). Everything is working. And yes, check out the Q811 and similar on the other shoulder. On my Monica, the backlight also shone right away, the Q811 case was with a hole. Q805 and Q812 replaced without thinking

Zyuyu: two thousand for BENQ in my opinion a bit too much. 1500 max.

In this section you will find BENQ monitor circuits and you can download... Moreover, you can download any of the schemes completely free, no registration, without sending SMS, directly from our website, without file sharing and other hidden tricks.

diagrams at the bottom of the page in attachments

All files are checked by antivirus!

Perhaps the following information will be useful to you:
* If you need programs for viewing downloaded files, you will find them in the SOFT section
* If you have any questions about the repair, we invite you to the FORUM
* If you are looking for where you can find specialists at the place of residence, go to the RADIOKOMPAS section
* If you yourself are engaged in repairs, then you have the opportunity to report yourself in the Radio compass section - just contact the FEEDBACK section

Monitor circuit BENQ E2400hd

Monitor circuit BENQ Q9T4
FP91GP chassis

Monitor circuit BENQ Q5T4
FP51G chassis

Monitor circuit BENQ Q7T4

Monitor circuit BENQ Q7C4
FP71E chassis complete manual

Many users are faced with the problem of no picture on the BenQ monitor. What is the cause of this malfunction? Let's consider the main problems and how to fix them.

If there is no image on the monitor screen, the first step is to determine what the problem is: the monitor or the computer system unit. To do this, follow a series of simple steps:

1. Disconnect the HDMI or VGA cable (whichever interface is used with your particular model).
2. Plug the monitor power cord into an electrical outlet.
3. Press the power button and notice the LED indication.
4. BenQ monitors usually display “Signal Cable not connected”. If a warning notification appears on the screen, the monitor is fully functional. In this case, the cause of the malfunction should be looked for in the computer system unit or in the connection to it.
5. If nothing appears on the screen, press the Menu button. If after that the image does not appear, most likely the monitor is faulty (usually, in such cases, the LED does not light up). The most common malfunctions of LCD monitors: failure of the power board, breakdown of the backlight and / or matrix. Unfortunately, in this case, you will have to contact the service center for further diagnostics.

If the monitor spontaneously turns off, this usually indicates a malfunction of the power supply (the LED may blink). If there is not enough voltage to backlight the screen, the monitor will try to turn on, but will turn off immediately. In this case, the power supply unit must be replaced.

Be careful! There is a high-voltage capacitor on the power board of the BenQ monitor, which, even when turned off, can maintain voltage up to 1000 V. Therefore, in the absence of experience and specialized tools necessary for repair, use the services of a service center.

If noise or interference appears on the screen after connecting the display to your computer, the video cable is likely to be loose. Try removing and reinserting the plug into the jack on the monitor. Do the same with the plug connected to the jack on the computer. Replace the cord with a new one if necessary.

If replacing the VGA or HDMI cable does not solve the problem, then power noise has entered the imaging circuitry. Usually this problem is corrected by installing filters on the monitor power board. The service center will be able to carry out the necessary diagnostics and make repairs.

In the event of a breakdown of the LED backlight or a malfunction of the power circuit, the image on the monitor may be present, but it is very dark and indistinct. Usually, the inverter, which is responsible for the formation of high voltage, fails, without which the LED backlight will not work. It happens that the backlight disappears not on the entire surface of the screen, but only in the corners, or vice versa - only in the central part.

In the event of a breakdown of the LED backlight (it happens quite rarely), it can be replaced with an LED strip, which is supplied with its own inverter. If the user is not familiar with the structure of the internal components of the monitor and does not have the necessary experience in repairing this kind of equipment, it is better to entrust all the work to professionals.

If the monitor is working properly, but refuses to work with a specific computer, you should check the correct operation of the video card and RAM strips. To do this, follow these steps:

1. Turn off the system unit and disconnect it from the network (required!)
2. Unscrew the screws holding the side panel of the system unit and remove it.
3. Slide the RAM latches and remove the microcircuit from the socket.
4. Unscrew the screws securing the video card and remove it from the connector.
5. Use an eraser to clean the video card pins and RAM.
6. Clean the inside of the computer from dust.
7. Blow out the video card and RAM connectors.
8. Install the microcircuits in their place.
9. Build your computer and turn it on.
10. Check display function.

There is a possibility that image problems may be related to incorrect BIOS operation. To restore its functionality, you must perform a factory reset. To do this, follow a simple sequence of actions:

1. Unplug the power cord from the mains.
2. Remove the side panel of the system unit.
3. Locate the CLRTC jumper on the motherboard (usually located near the BIOS battery).
4. Move the jumper from position 1-2 to position 2-3 for 15-20 seconds, then put it back in place.
5. Build your computer and turn it on.
6. Check the image on the monitor.

Be careful! Dust trapped inside the computer contains static electricity that can damage the motherboard, graphics card, and other cards. Clean your computer in time and do not touch the microcircuits with your fingers.

If none of the advice given in this section helped, and the monitor does not connect to the computer, the video card or motherboard is probably out of order. If the computer cannot turn on, the power supply is most likely defective. Contact the service center for additional diagnostics.

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 cuts power 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 backlighting, 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 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).

Author of the publication - = -
Heading: Repair and maintenance

Today in this article I want to share my experience of self-repairing an LCD monitor, the malfunction of which was turning on and off instantly, then the monitor turned on and off and so on ad infinitum, only sometimes after a while the monitor turned on and worked, but once it did not turn on anymore and I began to repair.

I purchased my 22-inch monitor back in 2008, 8 years have passed and some components could fail due to high temperatures inside the monitor, especially considering that a rather high temperature is reached in the area of ​​the power supply board, which also negatively affects the resource of electrical components.

It took me no more than 20 minutes to restore the monitor to work, and in this article I will tell you step by step the steps for self-repair.

I'm sure you've heard such a thing as "swollen" capacitors, this is the most common cause of failure of motherboards and power supplies of computers, but the boards of power supplies for LCD monitors are no exception, which convert the incoming 220 volts into 5 volts to power the electrical circuit and 14 and more volts for the operation of the matrix and the backlight inverter.

If your monitor is not new and you admit the possibility of failure of the capacitors in the power supply, you need to inspect their appearance, for this you need to disassemble the monitor, as a rule, there is a metal box inside, and under it there are two boards, one power supply (where the cord is inserted 220 volts), and the second board is actually the low-voltage part, which is responsible for the operation and control of the monitor.

If you have a multimeter at hand, then turn on the disassembled monitor and measure the voltage at the output of the power supply, usually the voltages that should be on a working monitor are written next to the terminals. In my case, I observed a voltage of 4.3 volts instead of the prescribed 5 volts, which already hinted at problems in the power supply.

Upon a cursory examination, 4 swollen capacitors immediately caught my eye, their parameters are 680 uF at 25 volts, I did not have any similar in size and capacity at hand, so I quickly packed up and went to the radio parts store.

The most important thing to consider when buying new capacitors is the capacitance, voltage, and dimensions. I decided to change all six capacitors and bought ten 1000 uF capacitors with a margin, for a voltage of 25 volts, the dimensions were identical to the old ones at 680 uF. Why did I put higher capacitors, you ask?

The fact is that in the output stages of the power supply, electrolytic capacitors play the role of smoothing the impulse voltage and by increasing the nominal capacity by 50-100%, you get a smoother voltage and a margin of capacity.

Next, I evaporated all the old capacitors and soldered the new ones. I would like to draw your attention to the fact that electrolytic capacitors have polarity, i.e. it doesn't matter how you solder them. Usually on the printed circuit board there are markings for the negative contact, and on the capacitor itself there is a designation for the negative terminal, so be careful, your task is to solder the new capacitors strictly observing the polarity.

After we soldered the new capacitors and made sure that there are no closed paths after working with a soldering iron, we turn on the monitor to the network. The LED lit up and no longer blinked. those. I already realized that the monitor worked, but to make sure I measured the output voltage, as you can see, it was already the required 5 volts. Then I connected the wires, made sure that the monitor works and no longer turns off on its own, and put everything in reverse order.

And finally, I want to give the data on measurements of the capacitance of the evaporated capacitors. Let me remind you that a total of six electrolytes were replaced, four of which had obvious signs of "bloating", their top side was not flat and round. So, so that you understand what a swollen capacitor is, I will give the following measurement results: the capacity of faulty capacitors ranged from 16 to 90 μF, instead of the nominal 680 μF.

Thus, we can say with confidence that in my case, the external sign of a slight swelling of capacitors was a consequence of a loss of capacity by more than 90%, which entailed an unstable low voltage, which prevented the start of the monitor backlight inverter, which is why the monitor turned on and immediately turned off due to the fault voltage dips. If you still have questions, you can ask them in the comments below to this article.

Recently I got a nice NEC LCD-1703 LCD monitor.

This monitor has served people with faith and truth for a long time, and then it stopped showing the image.The reasons for the breakdown of equipment can be different. One of these reasons may be the programmed accelerated aging of technology, laid down by manufacturers to enrich themselves for their loved ones. Instead of the usual picture, various stripes appeared on his screen. Then the image disappeared completely. The screen seems to be illuminated by a white background with vertical color stripes. After a while, he generally began to turn on only for a couple of seconds and turn off immediately. There is no external damage, the monitor is powered. Taking a screwdriver in my hands, I decided to look and try to fix the malfunction of the monitor in order to bring it back to life.

To get to the inside of the NEC LCD-1703 monitor, you need to remove its stand-leg by unscrewing four screws.

Mount the monitor stand NEC LCD-1703 M

Next, you need to put the monitor on a flat solid surface with the screen facing down. It is advisable to put something underneath that will prevent the screen itself from being scratched. I put the monitor on the table, and under the screen I put the foam wrapped around new monitors and televisions. This film is similar to floor and wall insulation. Next, unscrew the five screws securing the back cover of the monitor - four in the corners, and the fifth we will see in the center, where the monitor leg is attached.

Screws securing the back cover

In addition to screws, the rear cover mount also has plastic clips (as on many other audio, video, photographic equipment, cell phones). The photo showed one of them.

Plastic mount for the back of the monitor

These mounts are symmetrically positioned. Gently pick it up with a flat object through the slot of the front frame and back cover and remove the cover. After that, we have the following view:

Monitor without back cover

The circuit boards themselves that we need to check are under the metal shielding shroud. The cover is secured with screws:

and a screw-on VGA connector:

VGA connector screw

We unscrew these fasteners, remove the protective casing. We carefully examine the boards:

View of the monitor boards after removing the shielding casing

ATTENTION. Do not forget that even when disconnected from the power outlet, the internal parts of radio electronic equipment can remain under the life-threatening voltage of 220 volts. Before proceeding further, make sure that there is no residual charge on the capacitors. A household incandescent lamp can be used to discharge the capacitors. To do this, we connect both contacts of the lamp with wires to the terminals of the capacitor for a few seconds.

On the board, we check for burnt tracks and swollen capacitors. In my case, the capacitors of the monitor power supply were swollen:

Swollen capacitors of the monitor power supply

To replace the capacitors, we need to remove the power supply board by first disconnecting all the cables from the board and unscrewing the screws that secure it to the case. We solder the swollen capacitors:

The culprits of the non-working monitor

Three of the four capacitors were swollen, but I bought all four, since they are not expensive, and I did not want to disassemble and assemble the second time. Capacitors are needed two for 1000 uF 16 volts and two for 470 uF 16 volts (1000 * 16v, 470 * 16v). I bought four famous brand capacitors for 25 rubles, I did not take very cheap Chinese ones, not that savings). Having re-soldered the capacitors, we assemble the monitor in reverse order.