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Why does the computer turn on but not boot? The computer does not turn on. The procedure for cleaning the system unit

The trouble described in the title of the article happens to every computer sooner or later: one day it stops turning on. Sometimes this is preceded by some event, and sometimes absolutely nothing. In some cases, such failures are corrected very easily, while in others they are difficult to fix. In short, the range of problems that lead to a PC not turning on is very wide. Let's talk about them in more detail: what causes them, how to find the cause and deal with the problem yourself, without resorting to the help of specialists.

When someone says that their computer does not turn on, know that by this complaint the owner may mean the following:

The PC really does not turn on: there is no response to pressing the power button at all.
The PC turns on, but not completely: sometimes this is limited to the indicators on the system unit and keyboard turning on, sometimes to the sounds of the system speaker, sometimes when you press the power button, the fans start working, and then nothing happens. There is one common detail - the screen remains black.
The PC turns on and immediately turns off or goes into an endless reboot until the picture appears on the screen.
The PC turns on and works, but does not start on it operating system.

The first 3 situations are of hardware origin, that is, they are associated with a malfunction or incorrect connection of the equipment. The latter is most often caused by operating system errors that arose, for example, due to an unsuccessful Windows updates 7 to Windows 10, as well as device driver failures. In the case of drivers Windows startup usually interrupted by a blue screen of death - BSOD.

In more rare cases, the inability to load the OS is also associated with hardware problems - usually RAM or hard drive.

Reasons for true non-inclusion

Since failures to load operating systems are a separate big topic, we will not dwell on them in detail. Let's look at the reasons for the first three situations and, in addition to them, one more: turning on the computer not the first time, but after multiple clicks on the power button. So…

The computer does not respond to the start button

There is no power from the mains (the outlet or device through which the computer is connected to the power source - the UPS or surge protector - is not working). The only reason not related to a PC malfunction.
The power supply does not produce the required voltages because it is faulty, insufficiently efficient, or not powered from the network due to a damaged electrical cord.
Poor contact in device connectors, damage to power cables inside system unit.
Low battery voltage for BIOS chips.
Short circuit in one of the devices.
Malfunction of switching circuit elements on motherboard.
The power button on the system unit is faulty.
Blocking switching on by static charge.

The computer does not turn on completely (no initialization)

The elements of the video subsystem are faulty (video card, monitor, video cable). The absence of an image on the monitor, even if everything except video is working, in the eyes of the user looks like the computer not turning on.
The BIOS firmware has crashed (on some laptops, the BIOS crash is manifested by a complete lack of response to the power button).
The board has a faulty or unsupported processor installed.
The processor power supply system (VRM) is faulty.
The RAM or its batteries are faulty.
On old motherboards, the north bridge or bridge power supply has failed.

The computer turns off immediately after turning on or reboots cyclically early in the startup phase

BIOS meeting.
Overheat.
RAM defects.
The same reasons as for the complete lack of response to the button.

The computer turns on only after pressing the button multiple times

If the machine is older than 5-7 years, the life of the electrolytic capacitors in the power supply, on the motherboard or devices connected to it is exhausted.
The power button is faulty (the contacts are coming off).
Elements of the circuit starting the board or powering high-load components are faulty.

Diagnosis at home

Home users typically do not have equipment that can make troubleshooting easier, so they are left with the use of their senses and spare, known-good parts.

Before starting a diagnosis, it is important to remember what preceded the problem and what could have caused it. For example, the computer suddenly turned off during a thunderstorm and will not turn on again. Reason: burning out network controller high-voltage lightning charge through a twisted pair cable. If it stops turning on after some manipulations in the system unit - connecting a new device, cleaning it from dust, etc., the reason is most likely due to incorrect assembly or broken contacts of the devices.

If there is no obvious cause-and-effect relationship, for example, yesterday you turned off the computer as usual, but today it did not turn on, start checking with external contacts— the cord of the power supply, monitor and everything else that is located outside. In such cases, the following technique often helps: turn off the machine from the outlet or using the key on the power supply (i.e., disconnect from the power source) and hold down the power button on the system unit for 20-30 seconds. This will remove the static charge accumulated inside, which sometimes blocks starting.

Narrow it down possible problems The squeak of the system speaker helps: decoding of the sound signals is easy to find on the Internet. But keep in mind that BIOSes different manufacturers“squeak” differently. If the computer does not beep at all, it either does not have a speaker, or due to a malfunction (usually the power supply or motherboard) it is not running the BIOS microcode.

In cases where you cannot decide where to “dig”, use the algorithm that we present below. After each diagnostic step, try turning on the computer.

Inspect the system unit and all its connections from the outside. Disconnect unnecessary peripherals and everything connected to USB, except the keyboard and mouse.
Remove the cover of the system unit and make sure the internal connections are secure. If there is any accumulation of dust, remove it. If the motherboard is older than 3-5 years, replace the BIOS battery (brand CR-2032, sold in kiosks).

Without pressing the Power button on the system unit (with the power supply plugged in), if possible, check whether the motherboard is receiving standby power (for example, Asus has a standby LED indicator). Check by hand the temperature of large elements of the motherboard, video card and expansion cards. Normally they should be cold or slightly warm. If any part becomes noticeably hot, it is very likely that it is the source of the problem.
Turn on the power of the system unit. Pay attention to how the fans behave. Normally, after spinning up, they should slow down a little. If you see exactly this picture, the reason that there is no image on the screen is 80% likely to be a problem in the video subsystem. If the coolers are operating at maximum high speed, the reason is a failed BIOS, a “broken” RAM, a non-working/unpowered processor or a north bridge (on old motherboards). If the coolers make several revolutions and stop or only have time to jerk once, the source of the problem is a short circuit on any of the devices or poor contact at their connections. Cycles of spin up and stop running one after another (rebooting the computer at an early stage of startup) are usually due to damage to the BIOS. If the fans are not spinning at all, they are most likely not receiving power. This often happens when the power supply or motherboard is faulty.

If there are no signs short circuit(when they are, further diagnostics should be continued only after it has been eliminated), turn off the computer's power and reset the BIOS settings to default.

If the above algorithm does not clarify the situation, it is more convenient to continue further diagnostics on a stand assembled on a table.

Assembling the stand

Before removing components from the case, do not forget to turn off the power to both the system unit and the monitor - turn off the surge protector or unplug the cords from the outlet. If the computer is powered by a UPS, simply unplugging it from the outlet is not enough, since the batteries still have a charge.

Next, prepare workplace. The table on which you will assemble the stand must be dry and clean. It is not necessary to use special antistatic mats; it is enough that there is nothing metal on the table. To prevent electronic components from being damaged by static from your body, it is advisable to wear an antistatic wrist strap. If it’s not there, it’s okay: just touch any unpainted part of the PC case with your hands.

When removing each part, inspect it for:

chipped elements;
integrity contact groups(the presence of broken and bent contacts, melted or darkened plastic pads from overheating);
deformed and defective components (swollen capacitors, traces of leaked electrolyte, microcircuits with stains, and especially burnout holes);
darkening on the PCB (yellow or brown spots often appear on the back of the board under very hot elements).
scratches (if the scratch is above the tracks, look at it under a magnifying glass with maximum magnification to make sure that the tracks are intact).

Any of the listed defects may cause the PC to not work.

On machines that turn on for too long, every other time or after multiple reboots, pay special attention to the capacitors and the condition of the PCB underneath them. Thus, electrolytes that have outlived their useful life may look normal, indicating a malfunction only as a small dark spot on the back of the board.

If there is any suspicion of the unsuitability of electrolytic capacitors, they should be replaced with new ones, and not only obviously defective ones, but all those that are in the same circuit with them.

Having finished inspecting the devices, assemble a stand with minimal configuration on the table. For a test run, all you need is a motherboard with a processor and a cooler, one memory module, a power supply, a keyboard and a video card (if you are using a discrete one, and the processor or board has built-in video, connect the monitor to the latter).

When assembling the stand, it doesn’t hurt to clean the contact combs of the RAM and expansion boards with a school eraser. This will remove oxide deposits from them, which worsens contact in the connectors.

Turn on the power supply (if it is working properly, the board should start receiving standby voltage). Check the temperature of the components again with your hand. It should not be hot, as you remember, normally.
If you are in doubt about the functionality of the power supply, replace it with a known good one (if available). If this is not the case, try running it separately from the system: disconnect the 24-pin connector from the motherboard and connect a load to one of the free connectors, for example, optical drive or a regular light bulb with soldered wires. On the block that connects to the motherboard, close the contacts opposite the green and one of the black wires. If the load shows signs of “life” and the fan in the unit itself starts spinning, you can consider it conditionally operational.

To avoid electrical injury, do not open the power supply, even if it is turned off. Capacitors in the high-voltage part of its circuit can retain a charge for quite a long time.

Start the stand (remembering to return the working power supply to its place). This time not from the power button, but by closing the contacts to which its wires are connected on the board. If a picture appears on the screen (the computer is working), the cause of the problem is in devices that are not currently connected to the stand. If a monitor that is known to work does not turn on, the failure occurs due to the fault of one of the devices involved.

How to identify a problem node using indirect signs

If your computer has several memory modules, try running the test bench with each one in turn, installing them in different slots. If one of the combinations works, update BIOS firmware. After this, perhaps the rest of the memory will work.
If none of the RAM modules made the stand turn on, try running it without memory at all. In this way you will check the conditional “liveness” of the BIOS. “Live” firmware will make itself known by the squeaking of the system speaker or the blinking of indicators on the keyboard or motherboard.
Install a known-good and compatible processor on the bench. If the computer turns on normally, update the BIOS. Perhaps the processor that was installed before was simply not recognized by the system.
If you are using discrete video card, check it in different slots (if available), and also connect it through another video output to another monitor input.
If everything described above does not help you identify the source of the problem, the culprit is most likely the key component - the motherboard.

What to do with the device that caused the failure? The choice is small: replace it with a new one or take it to a service center for repair.

The situation when the computer does not turn on is, of course, not pleasant. Sooner or later this can happen to any PC. But if you want, you can find a way out of any situation, the main thing is not to panic, soberly assess the situation and begin to act.

Let's figure out how the problem of the computer not turning on can manifest itself, what the reasons may be, and how to find a way out of this situation.

She can manifest herself in different ways:

When you click on the “Start” button, the computer is completely silent;
It starts up, but it doesn’t go beyond the black screen and a beep is heard;
After a seemingly successful switch-on, it turns off after a few seconds;
Everything seems to be working, but only a black screen is visible;
At the stage it would seem successful download, a blue screen suddenly appears with many incomprehensible codes, and the situation is not corrected.

The causes of these problems may be:

Lack of 220V voltage in the network;
Power surges;
The power button is out of order;
Problems with the power supply;
Problems with hardware devices (faulty, device conflicts);
The CMOS battery of the BIOS memory is dead;
Not correct settings BIOS;
Overheating of the processor and video card;
Out of order motherboard;
Problems with cables;
Windows has crashed or there is a conflict at the software level with device drivers;

Now let's look at each situation in more detail.

The computer is completely silent

When the computer does not react at all to the power button, and yesterday it was still working, then you need to go from simple to complex. And you need to start from the outlet.

Make sure that it is 220 V, and not 360 or 150, there have already been precedents, so don’t laugh.

The computer may not start even at a voltage of 210V, it all depends on the quality of the power supply.

There are power supplies (PSUs) that have a special switch on the back side.

Check if it is enabled.

There are also models where you can switch the input voltage level - 127 and 220 V.

127 V, this is for countries where such a voltage is provided in the network, for example the USA. These types of devices are typically used by people who frequently change jobs while moving around the world.

If everything is fine and 220 V is suitable for the computer, then the latter will have to be disassembled.

Power button

Button task START – POWER Briefly short-circuit the wires coming from the system board.

View of the button with the front cover removed.

At the end of the wires there is a chip that fits onto the contacts. Find these contacts along the wires, see.

Check that the chip is tightly put on and well fixed on the contacts.

Take it off and put it back on. If this does not give any results, carefully close the contacts together with a screwdriver. Don't be afraid, there is no 220V, but the screwdriver should still have an insulator. God protects those who are careful.

Watch the video at the end of the article.

If the computer starts up, then check the wires going from the system board to the button and if everything is fine with the wires, then change the button.

If you have a tester to check Power button, you can go an even simpler route.

Set the tester settings as shown below.

And press the START button – POWER. If everything is normal, then you will hear a characteristic sound from the tester, which means the circuit is closed; if there is no sound, then there is a break somewhere.

power unit

If the computer does not turn on, then one of the main reasons for this may be a faulty power supply.

The main sign that the power supply is producing at least some voltage is the glow of the indicator lamp, which is located on the system board.

Modern power supplies are connected to the motherboard via 20 or 24-pin ATX connectors.

In our case, the connector is 24 pin.

And the plug is 20-pin - it would be correct to say an ATX connector.

There's nothing wrong with that. Simply, such a plug is connected to a 24-pin connector with an offset to the extreme left position. In this case, 4 contacts remain unused.

When the computer is connected to the network, a voltage of 5 V is supplied to the system board through the auxiliary power supply converter. The indicator lamp on the motherboard “tells” us this.

But it happens that there is no such indicator, so you need to check whether at least some voltage reaches the system board.

Take a tester and set it to the settings shown below.

Disconnect the ATX connector from the system board and connect power to the computer.

Using the diagram indicated above, we are looking for a voltage of 5 V that should reach the system board.

We also find out whether 5 V voltage is supplied to the PS_ON contact.

Again, using a tester, we check if there is voltage at certain contacts of the ATX connector.

If in at least one of the cases there is no voltage, or it is not significant, then the problem is in the power supply.

If you want to figure it out yourself, then look for the reason in the resistor of the unit itself. It has a resistance of about 1 kOhm and the so-called standby voltage of 5 V passes through it.

Power supply resistors are different. Replacement must be carried out only with an identical brand. Some characteristics of resistors can be seen below.

To avoid any doubts, if possible, install a different power supply on the computer, in 99% of cases this clears up the situation.

What is PS_ON

PS_ON is a signal that unlocks the start of the main power supply converter to turn on the computer.

When the computer is turned off, as we have already found out above, there is a voltage of five volts at the PS_ON contact.

When you press the START - POWER button, a signal of the same name is sent from the system board to the PS_ON pin.

This signal resets the voltage at the PS_ON pin to zero (0 V) by shorting it to ground, thereby signaling to the power supply to turn on the main converters.

The power supply begins to produce current of the specified parameters, powering all computer systems with it.

If given parameters voltages for some reason exceed the permissible values, for example, as a result of a short circuit, then the main converter stops working and the computer turns off.

It is worth mentioning the PW_OK signal, without which the computer cannot operate. When the computer is turned off, the voltage at the PW_OK contact is 0.

The power supply receives the PS_ON signal from the motherboard to start the main converters.

At this moment, two voltages 3 and 5 V are formed in it, which, in turn, begin to increasingly form a signal PW_OK having a final voltage of 5 V + – 0.5 V.

Signal formation time is from 0.2 to 0.5 seconds. This is the time during which a stable voltage will be generated in the power supply to start the processor and other devices.

After the required voltage indicators have been generated, the PW_OK signal is sent to the contact of the same name and then to the motherboard, where signals are already generated to set the initial parameters of the processor, and then the computer is fully turned on.

The 5 volt PW_OK signal always exists as long as the PC is running. It seems to tell the system that the voltage is “OK” and you can work.

If the network voltage drops or rises and the power supply cannot cope with these surges, the PW_OK signal changes its performance.

Usually the voltage decreases to 3 volts or less, making it clear to the system that the voltage is not stable and operation is not possible.

Then starting the computer will not be possible or it will safely turn off due to the fact that the signal to stop the processor will arrive before the main voltage is lost.

How important is the PW_OK signal?

The first attempt to turn on the computer was unsuccessful, what is the reason?

First, let's figure out how the PW_OK signal can affect freezes and errors when turning on the computer?

What do you think when a car has high fuel consumption, when it is just starting to drive or when driving on the highway at the recommended speed?

The answer is obvious, of course at the start.

The same thing happens when you start the computer. In the first seconds, the starting current is much greater than that consumed during its further operation.

For example, at startup a computer can consume up to 300 W, and in operating mode 150 - 200.

At the moment of start, all transistors, capacitors, chokes are switched on, and the process of filling the circuit with energy is underway.

In this situation, the power supply tries to stabilize the voltage as best as possible and reduce the current ripple, which is very large.

If at this moment you apply the PW_OK signal to turn on the processor, then malfunctions may occur in its operation, and therefore in the memory CMOS BIOS.

For this purpose, a delay is provided in the formation of the signal (command) PW_OK.

The first sign that this command is formed very early, this is when the first attempt to turn on the computer fails, and when it is restarted with the Reset button, the boot process returns to normal.

You can also use hotkeys Ctrl+Alt+Del.

There are several results:

A low-quality power supply unit is installed on the computer;
It needs to be repaired or replaced.

Restarting the computer

Let's say an attempt to turn on the computer is successful, but after a while it starts to reboot.

What could be the reason?

As we said above, the PW_OK signal is constant when the PC is running. It is equal to 5 V, provided that the network voltage is standard, for our country it is 220V.

If the mains voltage drops, the PW_OK signal may disappear or decrease. This stops the PC from working before its systems notice any problems on the network.

When the network voltage normalizes, this problem will go away by itself. Therefore, it is recommended to use uninterruptible power supplies for PCs to stabilize the voltage.

Let's check the power supply further

In this situation, it is necessary to check whether voltage is supplied to other PC devices, in addition to the motherboard, through the ATX connector.

Common types of connectors on the power supply, in addition to the ATX connector.

We check the presence of power at the connectors, starting with the most important ones.

With the computer de-energized, disconnect the processor power cable from the system board and connect the tester probes to its connectors.

Connect your PC to the network and press the START – POWER button.

In both cases, the DC voltage should be within 12 V.

If there is no voltage, or it is significantly less (5.7V), then you should think about the health of the power supply.

Using the same method, we check the motor power connectors. hard drives, disk drives, etc.

If the voltage is below standard, then the power supply is clearly faulty.

The computer turns on but there is a beep

If you hear that the computer is working, but the system does not boot, and beeps are heard, then there are problems with the hardware devices.

If there are no signals, then check whether there is a special speaker on the motherboard.

If it is not there, then try to get one and connect it to the Speaker connectors on the system board.

There are situations when the speaker burns out, then you just need to replace it.

The signals emitted from the computer may vary. It all depends on the BIOS version that is flashed into the CMOS memory.

It is advisable to have such data on hand, or look it up in the documentation for the motherboard.

You can also, if your computer is still working, go into the BIOS and write out its version from there.

Common BIOS versions:

Phoenix;
Award;
Compaq;
Dell;
Quadtel.

For example, when you turn on the computer, you hear 1 short and 1 long signal. Version BIOS Award.

We look at the table and see that there is a RAM error.

We open the computer, pay attention to the RAM strips and see.

One strip is installed incorrectly.

We are correcting the error.

The bracket is inserted correctly, and as a result, the computer starts without problems.

There are situations when one of the RAM strips fails. It will not be possible to detect it by sight. It is necessary to remove each strip in turn and try to start the PC.

If there is only one strip, then it must be replaced with a similar one (DDR, DDR2, DDR3, DDR4), don't get confused. It is advisable that all RAM sticks be from the same manufacturer.

Incorrect BIOS settings

BIOS settings are a separate, very extensive topic. If the computer has stopped loading and some message appears on the black screen, then it does not just appear.

Study it, then the picture will become more or less clear.

A common problem when turning on a computer is that the operating system boot source is incorrectly set in the BIOS.

There may be several of them: from the hard disk (HDD), from DVD, from a USB source and from the network.

Check how these settings are configured. If the system, for example, is not installed from scratch, then the first boot source should be the HDD.

This often happens when a USB drive is set as the primary boot source, and a regular, non-bootable flash drive is inserted into the computer. This may cause an error.

Many PC users do not even know that there is a battery on the motherboard, due to which the computer may not start due to its low voltage.

The CMOS memory in which the BIOS resides is not non-volatile. For her stable operation A 3 volt battery is provided. It is easy to find on the system board.

Its working time is up to 5 years. The first sign that the battery is running low is that the time on the computer constantly lags for no reason.

Typically, the battery model CR2032, it costs a penny and changes in a few seconds.

But the problem may be different. As a result of blackout CMOS memory in BIOS, even for a short time, all BIOS settings can be reset.

Therefore, you will have to set them again. If you don’t understand, then just set the factory default settings.

To do this, depending on the BIOS version, look for “Load Optimized Defaults” or Load Default Settings. Keywords"Load Defaults".

Overheating of the processor and video card

The importance of a computer cooling system can hardly be overestimated, especially when it comes to cooling the processor, video card, north and south bridges system board.

The processor is protected from overheating by a special cooler, which you need to know how to use.

But as a result of incorrect selection of the latter, its failure or heavy dust, the processor may overheat.

To prevent the CPU from burning out, it is protected, which turns off the computer when this danger occurs.

Therefore, if you notice that a few seconds or even minutes after turning on the PC, it turns itself off, look into the system unit.

Most likely you will see a picture like this there.

After cleaning the system unit from dust, the situation can be corrected, but not always.

If the computer shuts down continues, you will have to remove the cooler and get to the processor.

Remove the latter and look at the condition of the thermal paste.

Over time, it dries out and does not perform the function of improving heat exchange between the CPU and the cooler radiator.

Using alcohol or cologne, remove the old layer of thermal paste and replace it with new one.

In the case of a video card, the PC will not restart. Most likely you will only see a black screen or hear beeps.

If you are sure that the monitor is working properly, remove the video card and clean it from dust.

Don't forget to remove the old thermal paste and apply new one. She's there too.

Also, the failure of the video card is the reason that the monitor screen is black and the boot process can only be seen at the BIOS boot. But we'll talk about the monitor next.

Other devices

We have already briefly touched on problems with RAM memory sticks. All copper contacts of any devices tend to oxidize, especially if the room has high humidity.

Therefore, they need to be cleaned periodically. To do this, you can use a regular hard eraser.

Also don’t forget about network cards, TV tuner, WI-FI adapter and other devices, if they are on the computer.

If after cleaning the contacts the computer still does not turn on, then remember what device was recently installed on the system board. Dismantle it.

If this does not help, then use the method of elimination. Starting with the least significant devices, remove them from their slots and try to turn on the computer. If this does not help, move on to the next subsection.

System board

The presence of dust on the motherboard can lead to overheating of the north and south bridges, as well as other microchips.

Therefore, you need to clean your computer from dust at least once every 4-6 months.

The culprit for the failure of the motherboard may also be a poor-quality power supply.

Conclusion, you shouldn’t skimp on the power supply.

It is difficult to visually determine that the motherboard has failed. Although if you look closely, you can find the reason.

Replacing the motherboard can lead to a complete upgrade of the computer, and that's not cheap. It is worth repairing only when its repair does not exceed 50% of the cost of a new one. But everyone makes the decision themselves.

Loops

Loops rarely fail and, as a rule, the problem lies not in them, but in the places where they are connected.

It is especially worth paying attention to the cables: a seven-pin data cable and a fifteen-pin additional voltage cable.

Their disadvantage is weak fastening. Have you moved the system unit? Did you hit him with your foot or cleaning equipment? After this your computer won't boot?

Check the SATA cables to see if they have come loose from the hard drive and motherboard. Disconnect and reconnect them. As a rule, this solves the problem.

Blue screen

Subject blue screen at booting Windows is very extensive and it is impossible to reveal it in this, and so not small, article.

The problem with this may lie in the plane of both hardware and software failure.

As a rule, it is solved by dismantling some hardware devices. For example, you have a motherboard from MSI and a video card from ASUS.

But incompatibility between devices from different manufacturers, although it does occur, has recently become extremely rare.

Also the latest installed drivers may cause the system to crash, etc.

This problem is solved by rolling back the system, through safe mode boot, system restore from boot disk or a specially created Windows recovery disc.

But we will definitely talk about this in another article.

Of course, the monitor cannot directly affect the problem with turning on the computer. But when a black screen appears, it is still worth paying attention to.

Its unexpected failure can mislead you even against the background common problem, there is a high probability that you will take a different path to find its causes.

The classic operating voltage for monitors is 12V. If the device’s power supply is external, then checking the output voltage with a tester is not difficult.

There were cases when the monitor showed signs of its operation (LEDs of the connected network), but when checking the power supply with a tester, the latter produced only 7 volts.

As a result, the problem was solved by replacing the monitor's power supply.

Bottom line

We looked at the main reasons why the computer refuses to turn on and the operating system refuses to boot.

You need to understand that the main problem is not how to eliminate them, but how to identify them.

Continuing the topic of computer malfunctions, today we will tell you why the computer may not boot when turned on. In the previous article about computer malfunctions, you could familiarize yourself with the reasons why. Now it turns on, but the download does not start. Let's figure it out.

The moment you turn on the computer, the fans should, of course, spin and sound, and the disk activity indicator should light up. If this does not happen, then we do the following: turn off the computer, simplify the configuration to a minimum by disconnecting all expansion slots peripheral devices and adapters. If you have a pair or more memory modules installed, you can leave one or remove them all.

When you turn on the computer after these steps, you may hear a peculiar squeaking sound. This means that it has started. The power is turned on and the internal system routines begin to diagnose (the message Power On Self Test or POST appears), and audible signals indicate that errors are detected. These errors are justified, since you will remove video adapters from your computer, RAM.

How to make out sound signals?

Well, decoding depends on two factors - the manufacturer and the .

To give an example, one long and two short beeps indicate that the video adapter was not detected during the AWARD BIOS self-test. When no errors are detected, this is indicated by one long signal, which is used as standard for all BIOS versions.

If you want to learn more about computer sound signals, then the manufacturer’s websites will help you or read.

If you have created a minimal configuration for your computer, but there are no sound signals, the reason may be the power supply, motherboard or processor.

In this case, we recommend you try it. For this purpose, there is a corresponding jumper on the motherboard (Clear CMOS). Sometimes the cause of the malfunction may be swollen capacitors on the motherboard in the processor power supply circuit.

Each of us has at least once encountered problems when your computer suddenly stops turning on - the fans do not make noise, the front indicators do not light up. Or it turns on, but the monitor does not show a picture - it lights up black and displays the message “No signal” (translated as “no signal”).

In this situation, you should not despair and rush to the store to buy new equipment or run to service center.

In most cases, problems with turning on a PC can be resolved at home.

To do this, you need to find out what causes the problem of turning on the computer, as well as make diagnostics to identify the malfunction and carry out repair work (replacing faulty components).

This article will help you figure out what happened to your computer in each specific case.

When the PC is turned on, the fans do not make noise and the indicators do not light up.

You press the power button on the computer and there is silence. There may be several reasons why the computer refuses to turn on. Do the following simple things:

Check if the power cable is well connected to the system unit
Check if the toggle switch (Fig. 1) on the back of the computer is turned on
Make sure that the computer's power button can be pressed freely and does not stick when pressed.
Check your surge protector, extension cord and outlet for proper operation.

In rare cases, the network cable from the system unit turns out to be faulty when the wires inside it are broken. Check the cable with a multimeter.

Figure 1 - toggle switch in the "on" position

Switch it to resistance measurement mode, for example 200 Ohms. You may have different values, for example 100 Ohms. There is no difference - it is advisable to choose the lowest measurement. The cable plug has three holes. Measure the two extreme ones. The middle one is grounding - don't touch it.

Green oval - resistance measurement mode. Red circles - measured wires

If the wire being measured is intact, the multimeter shows numbers different from one.

The multimeter readings differ from unity, therefore the wire is intact

If the reading is “1”, this is a wire break.

There is an obvious wire break here - the multimeter readings are equal to unity

You can purchase a new cable at any computer store. The price ranges from 150 to 250 rubles

If all of the above methods did not help you, i.e. The computer is still “silent” - we will have to open it, we will look for the reason inside the system unit. This will be shown below.

The computer turns on, but the monitor is black.

The next problem is when the computer turns on and in front of you there is a black monitor with the words “No signal” means following problems:

The cable from the monitor to the video card is poorly connected
Video card is faulty
The RAM module is faulty
CPU processor faulty
The motherboard is partially damaged (the capacitors are swollen, the north bridge is burned out)

It often happens in practice that these problems can be solved by removing RAM from the slot and inserting

Taking out the RAM

back, as well as by removing and inserting the video card back. There is only one reason - poor contact of the memory or video card due to dust or oxidation of the contacts.

To be safe, you can take a washing rubber band and use it to clean the contacts of the removable board.

Cleaning contacts with an eraser

Then reinsert the removed cards and try to start the computer again.

If there is no positive result, then you will have to open the computer and look deeper for the problem.

When you turn on your PC, you hear strange “beeping” sounds.

When you turned on your computer, you probably heard one short beeping sound. It means that all the hardware in the computer (processor, RAM, video card, motherboard, various microcircuits, etc.) is fully operational and the computer is starting up. A short sound is given to us by the BIOS chip - a system that controls all electronic components in the computer, is responsible for the boot order of devices (disk drive, hard drive). BIOS system- this is a microcircuit that is soldered into the motherboard - Fig. 2.

Figure 2 - BIOS chip on the computer motherboard

If you hear other sounds when you start your computer, such as long and short sounds, various combinations this means that there are problems with the computer that need to be determined by sounds. BIOS sounds carry a certain malfunction, the decoding of which we will learn in the next section. Depending on the manufacturer of the BIOS chip, the sounds may differ.

Find out the BIOS brand on your computer

To correctly determine the error by sound signal BIOS let's determine which company is the manufacturer of the chip on your computer. To do this:

disconnect all wires from the system unit (in common parlance “processor”)
remove the side wall of the computer
look on the motherboard for a characteristic microcircuit as in Figures 3,4 and 5

Figure 3 - microcircuit BIOS company AWARD - quite common on many motherboards

Figure 4 - AMI BIOS chip - more often found on laptops

Figure 5 - Phoenix BIOS chip

BIOS Award Sounds

AWARD BIOS sounds are as follows:

AWARD BIOS is very common in many models of PC motherboards.

BIOS AMI sounds

The following sounds are distinguished:

Phoenix BIOS sounds

The sound encoding of this BIOS is deciphered differently from the previous two. The code consists of a series of sounds with a certain interval, for example the encoding 4-2-3 means 4 short, pause, 2 short, pause, three short sounds. New versions of this BIOS consist of four types of sounds.
BIOS sound encoding:

We take a screwdriver in our hand and disassemble the PC. We diagnose and fix problems

The most interesting moment has come - disassembling the computer and troubleshooting.

System unit without side wall

Now we will do diagnostics if the computer does not turn on at all.
The best place to start is by checking the startup of the power supply. Disconnect its plug from the motherboard, see Fig. 6.

Figure 6 - Power supply plug. The latch is circled in red.

Press firmly on the latch and pull the plug upward using a rocking motion.

Figure 7 - Removing the power supply plug from the motherboard.

Now you need to find a small piece of wire. Strip both ends of the insulation.

According to Fig. 8, insert one end of the wire into the hole of the plug where the green wire is and the second into any black one, thereby we will start the power supply without a computer. Let's check whether it works or not. The required wires are indicated by arrows in Fig. 8.

Figure 8 - How to correctly insert the jumper to start the power supply

Computer power supply

If the power supply does not start, it means it is burned out. Only a qualified specialist can repair it. The average cost of a new power supply (depending on power and quality) is from 2000 rubles to several thousand. Typically, computers have power supplies with a power of 450-500 Watts - their cost is from 2000 to 3000 rubles.

If the power supply starts up, that is, the fan spins on it and a click is heard during startup, there may be a problem with the computer's power button.

In Fig. Figure 9 shows the place on the motherboard where the connectors for the computer start button are connected, as well as the reset button, power indicator indicator work hard disk and speaker - BIOS making sounds

Figure 9 - the “+pws-” connector is marked with a red rectangle - it is responsible for connecting the computer start button

Disconnect it and look at the connector - it should have the inscription "power sw" on it as in the fig. 10

Figure 10 - power sw connector

Let's check the computer's start button for serviceability. Take a screwdriver and close the two needles in which the "ower sw" connector was inserted and removed.

If the computer starts working, it means the power button is broken and needs to be lured. It's hard to find such a button. often they are not sold. Most often, in such cases, users tear off the wires from the button and bring them out to the front. To start the computer, you need to close the wires for 1-2 seconds (do not twist) and disconnect.

If the computer still does not turn on, disconnect all devices connected to the motherboard.

And so, turn off the hard drive Fig. 11. Disconnect the two wires marked in the figure.

Figure 11 - arrows mark the power cable (left) and data wire (right)

We take out the RAM Fig. 12 Squeeze the latches at the edges, there are two of them

Figure 12 - in the red oval there is a lock that needs to be bent

Remove the memory module from the slot Fig. 13. If you have more than one memory module, but two or more, remove them all.

Figure 13 - Memory module removed from slot

Now unscrew the bolt securing the video card Fig. 14

Figure 14 - in the red circle there is a bolt securing the video card

Then bend the lock on the slot as shown in Fig. 14

Figure 15 - bend the lock

and carefully remove the video card.

Video cards successfully removed

All that remains is to remove the plugs of the USB ports on the front panel (Fig. 16).

Figure 16 - Front panel USB port plugs.

When you reinsert the USB connector, pay attention to the absence of one needle in the slot, marked in Fig. 17,

and also the absence of a hole is noted in the connector - Fig. 18.

Figure 18 - USB connector.

Then disconnect the drive and fans, if any are connected. And try to start the computer again

If this time the computer does not start, you should pay attention to the capacitors. In Fig. 19 shows swollen and normal capacitors.

Figure 19 - Capacitors on the motherboard. Normal ones are marked with green arrows. Swollen (faulty) - pink.

Figure 20 - This is what leaking capacitors look like.

Rice. 20 shows leaking capacitors.

Replacing capacitors by a specialist is usually inexpensive - about 200-500 rubles, depending on their number.

Such capacitors require replacement with new ones. Replacement must be carried out by a qualified technician.

Diagnostics of a computer that turns on and there is no signal on the monitor is done by removing the memory modules and video card. To do this, you need to have working components to check which of them does not work.

You can refer to Figures 12,13,14 to remove the faulty board.

The reason for the image not displaying on the monitor may be a faulty CPU processor.

It is hidden by the cooling cooler on the motherboard Fig. 21.

Figure 21 - CPU cooler (black fan and radiator underneath).

Everyone knows that processors are produced by leading companies INTEL and AMD. Depending on the processor brand, the cooler mount also varies.

Now we will explain the removal of the cooler and AMD processor.

Lift the foot on the cooler up - Fig. 22.

Figure 24 - Bend the processor clamp.

Very carefully pull out the processor without bending its legs Fig. 25

Figure 25 - We removed the processor.

Sometimes it happens that by removing the processor and putting it back, the computer can start when turned on. Be sure to do this operation. This may help you.

Also run the computer without a cooler. for 10-15 seconds. If the processor is cold during operation, it is likely that it has burned out.

It may turn out that the processor is intact and the socket (the seat where the processor is installed) is not working.

You can check the socket only if you find a similar processor for such a socket. You can find out what socket you have and what processor will suit you - all this can be found on the Internet. Entire topics are devoted to this issue.

What is CMOS checksum error?

You turned on the computer and saw an incomprehensible message CMOS checksum error on the black screen. No need to worry. This is not a critical error. It appears due to an incorrect date on the computer and the BIOS configuration settings have been reset. A small battery on the motherboard is responsible for all this - Figure 26. Your battery is low

Figure 26 - CMOS battery on the motherboard

You need to check it with a multimeter. First, let’s pull it out by carefully bending the lock with a screwdriver - Fig. 27.

Figure 27 - Taking out the battery

We measure the battery voltage with a multimeter - Figure 28. Switch the multimeter to voltage measurement mode.

Figure 28 - Measuring battery voltage.

Normal voltage 3 volts - if it is new. But the computer can work if the battery has 2.5 - 2 volts.

To replace the battery, you need to know its model; it is written on the battery itself - “CRC 2032” - look carefully at Fig. 26 - the inscription is visible under the arrow.

After installing a new battery, the CMOS checksum error may appear again. 29

Figure 29 - CMOS checksum error window

To do this, press the DEL key on your keyboard. This will take you to the BIOS settings - Fig. 30.

Figure 30 - Window BIOS settings

BIOS windows may vary appearance on different computers. The main thing is to find the parameter with the words Default.... Usually responsible for resetting the BIOS settings

In the right part of the window, use the keyboard arrows to select the topmost line “Load Fail-Safe Default” - and press Enter.

A confirmation sign will appear - press the letter Y and Enter again. To save BIOS settings, press F10. The computer will restart. All that remains is to change the date on the computer, because... it will be rewound several years ago due to battery replacement.

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