The computer turns on and stops. The computer does not turn on, but the fans of the system unit are working

Failure to understand the nature of certain computer problems often leads to errors in diagnostics, without which qualified repairs are impossible. And you should approach the search for a problem with its accurate description. A malfunction that is described by the words: “when you press the power button (power), the computer does not turn on, but the fans work” is called the absence or initialization error. It should not be confused with "not turning on" - complete inactivity on pressing power, since the causes of these two problems are usually different.

Initialization, in this case, is the readiness of the equipment for operation. And if any of the devices critical for starting a PC refuses to start, we will observe a characteristic picture:

• after switching on system block loud fan noise is heard (they rotate at a constant high speed);
• the keyboard and power indicators light up and do not go out;
• the screen remains black.

Nothing else happens.

The reasons

According to statistics, the most common source of such a problem is the following:

• BIOS corruption - a program stored in the CMOS flash memory chip on the motherboard responsible for bootstrap PC, as well as for checking and coordinating the operation of all its devices at the start stage;
• a failed processor or a malfunction of its power supply system;
• inoperability of RAM (RAM) or incompatibility of installed RAM strips with each other;
• chip failure system logic(chipset) on the motherboard, especially often - the north bridge.

Other reasons that can also give such a “clinic” include damage to the elements of the motherboard, leading to destabilization of the power supply of devices, a defect in the solder contacts of microcircuits, a power supply with a “drawdown” of voltage along individual lines, a dead CMOS battery, and other problems equipment installed on the PC. However, this is less common.

It is also important to understand that this problem is never the result of software failures in the operating system. Because it won't even start downloading.

Diagnostics

What can the user do in such a situation? Even without special equipment, you can try to solve the problem at home. It is enough to know how to use a screwdriver.

Reset BIOS settings to factory settings

This is the simplest and, at times, very effective way Troubleshoot booting problems. If your case is not the most difficult, perhaps it will help.

• turn off the computer power and remove the system unit cover.
• Locate the coin cell battery on the motherboard and remove it from the socket.
• close the contacts of the battery socket with each other, for example, with a screwdriver;
• reinstall the battery.

There is another option to reset the BIOS - a jumper (jumper) Clear CMOS. It must be removed and for 15 - 20 seconds. and move to two adjacent contacts, then return to its place. Sometimes the jumper is called differently: CL_CMOS, CCMOS, CLRTC, CRTC, etc.

After doing these operations, connect the power to the computer and try to turn it on. If the problem is fixed, its cause lay in the incorrect BIOS Setup configuration.

Turning off all unnecessary

If the first method did not help, move on. Let's try to exclude the influence of equipment that is not necessary for a successful PC start. To do this, you need to prepare a table covered with insulating material (polyethylene, rubber, plastic, wood, etc.) on which you will assemble the stand.

Let's get started:

• power off the PC and remove the case cover;
• remove the expansion cards from the motherboard slots, disconnect the power wires and interface cables from it, remove the memory strips;
• remove the motherboard from the case, put it on the table and inspect for artifacts - swollen capacitors, signs of overheating (darkening and deformation of plastic parts), mechanical damage and other defects
• if there are no artifacts, install one memory bar in the slot, connect a video card (if there is no built-in one), a monitor, previously extracted boot HDD and power supply;
• turn on the power supply to the mains;
• close the contacts of the power button with a screwdriver - Power Switch (can be signed as ON, PWR_ON, PC_ON) - this action is similar to turning on the computer by pressing this button.

If you see loading on the monitor operating system- it means that one of the disconnected devices is causing the failure. Well, if nothing happens except for the rotation of the fans, let's try to figure it out in more detail.

• Start the system. Gently touch the processor heatsink and large board components - chips, mosfets, etc. - they should normally be warm. Strong heating (do not burn yourself!) - indicates a malfunction of the elements (soldering defect, short circuit), and the complete absence of heating (room temperature) - most likely indicates that the node does not receive supply voltage.
• Power off your PC. Remove the memory bar, remove the oxide layer on its contacts by rubbing with a school eraser, blow through the slot where it was, and install it back. Turn on your computer. If the problem is solved, the reason was in poor contact between the RAM and the board connector. If you don’t dare, install the bar in another slot - perhaps he is to blame.

Replace parts with known good parts

None of the methods helped? The last thing that can be done at home is to replace PC devices in turn with working ones, of course, compatible with your system. However, there is a risk of damaging them.

If there is no such possibility or desire, and also if the described problem occurs on the laptop, the only remaining option is to contact the service center.

In the life of almost every user, there have been situations when a computer or laptop suddenly began to behave differently than before. This can be expressed in unexpected reboots, various interruptions in work and spontaneous shutdowns. In this article, we will talk about one of these problems - turning on and instantly turning off the PC, and we will try to solve it.

There can be quite a few reasons for this PC behavior. This is the wrong connection of cables, and careless assembly, and failure of components. In addition, the problem may lie in some settings of the operating system. The information that will be given below is divided into two parts - problems after assembly or disassembly and failures "from scratch", without outside interference in the computer hardware. Let's start with the first part.

Reason 1: Cables

After disassembling a computer, for example, to replace components or clean it from dust, some users simply forget to reassemble it correctly. In particular, connect all cables in place or connect them as securely as possible. Our situation includes:

Reason 2: Short circuit

Most power supplies, including budget ones, are equipped with short circuit protection. Such protection cuts off the power supply in the event of a short circuit, the causes of which may be as follows:

Cause 3: Sudden increase in temperature - overheating

Overheating of the processor during the system startup phase can occur for several reasons.

• Non-working fan on the cooler or disconnected power cable of the latter (see above). In this case, when starting, it is enough to check whether the blades rotate. If not, you will have to replace or lubricate the fan.
• Wrong or crooked installed system cooling of the CPU, which may cause the soleplate to not fully adhere to the heat spreader cover. There is only one way out - to remove and reinstall the cooler.

Reason 4: New and old parts

Computer components can also affect its performance. This is both a banal negligence when connecting, for example, an old video card or RAM modules, or incompatibility.

Check if the components are securely connected to their connectors, if additional power is supplied (in the case of a video card).

In terms of compatibility, some motherboards with the same sockets may not support previous generation processors and vice versa. At the time of writing this article, this situation has developed with socket 1151. The second revision (1151 v2) on 300 series chipsets does not support previous processors on Skylake and Kaby Lake architectures (6 and 7 generations, for example, i7 6700, i7 7700). In this case, the "stone" approaches the socket. Be careful when choosing components, but rather study the information about the hardware you are purchasing before buying.

Reason 5: Dust

The attitude of users to dust is often very frivolous. And it's not just dirt. Dust, clogging cooling systems, can lead to overheating and failure of components, the accumulation of harmful static charges, and at high humidity it begins to conduct electricity. About what it threatens us, it is told above. Keep your computer clean, and don't forget about the power supply (this is often the case). Clean dust at least once every 6 months, and even more often is better.

Reason 6: Power supply

We have already said that the power supply "goes into protection" in the event of a short circuit. The same behavior is possible when its electronic components are overheated. The reason for this may be a large layer of dust on the radiators, as well as a non-working fan. Insufficient PSU power will also cause a sudden shutdown. Most often, this is a consequence of the installation of additional equipment or components, or the advanced age of the unit, or rather, some of its parts.

In order to determine whether your computer has enough power, you can use a special calculator.

You can find out the capabilities of the PSU by looking at one of its side surfaces. In column "+12V" the maximum power on this line is indicated. It is this indicator that is the main one, and not the face value written on the box or on the product card.

It is also impossible not to say about the overload of ports, in particular, USB, devices with high power consumption. Interruptions are especially common when using splitters or hubs. Here you can only advise to unload the ports or buy a hub with additional power.

Reason 7: Faulty hardware

As mentioned above, faulty components can cause a short circuit, thereby triggering the PSU protection. It can also be a failure of various components - capacitors, chips, and so on, on the motherboard. To determine the faulty equipment, you must disconnect it from the "motherboard" and try to start the PC.

Example: turn off the video card and turn on the computer. If the launch is unsuccessful, we repeat the same with the RAM, only you need to turn off the strips one at a time. Next, you need to turn off the hard drive, and if it is not one, then the second one. Do not forget about external devices and the periphery. If the computer did not agree to start normally, then the matter is most likely in the motherboard, and the road to it is straight to the service center.

Reason 8: BIOS

BIOS is a small control program written on a special microcircuit. With its help, you can configure the parameters of the motherboard components at the lowest level. Wrong settings can lead to a problem that we are in this moment discussing. Most often, this is the setting of frequencies and (or) voltages that are not supported by the components. There is only one way out - reset the settings to factory settings.

Reason 9: OS Quick Launch Feature

Function quick launch, present in Windows 10 and based on saving drivers and the OS kernel to a file hiperfil.sys, may cause the computer to behave incorrectly when turned on. This is most often seen on laptops. You can disable it in the following way:

Conclusion

As you can see, there are quite a few reasons for the problem under discussion, and in most cases its solution takes a sufficient amount of time. When disassembling and assembling a computer, try to be as careful as possible - this will help to avoid most of the trouble. Keep the system unit clean: dust is our enemy. And the last tip: without prior information preparation, do not change the BIOS settings, as this may lead to the computer's inoperability.

In troubleshooting computer technology many phenomena and connections are not obvious. That is, completely different faults have the same external signs. Surely many of you have met with this form of "strike" of the PC, in which its work continues ... just a few seconds. In other words, switching on is followed by an immediate shutdown, and at the same time, a black "Malevich's square" appears on the screen.

Let's talk about the reasons why the computer turns on and off immediately, and what to do about it at home without special equipment.

Reasons for instant PC shutdown after startup

Traditionally, computer problems are divided into hardware and software. The former are caused by a hardware failure, the latter by the operating system and applications. The situation that we are considering today belongs entirely to the first category, that is, it is always connected with iron.

What can cause it:

• Unstable voltage in the household power supply, if the system unit is connected to it directly.
• Faulty power supply, broken power cord.
• Incorrect connection of any device inside the system unit - incomplete installation in the connector, separation of contacts, etc.
• Incorrect installation of the cooling system (the sole of the radiator does not come into contact with the surface of the processor) or its complete failure.
• Short circuit in any of the devices of the system unit.
• Damaged BIOS firmware.

As you can see, the range of possible culprits is quite extensive. Basically, anything can be the cause. To simplify the diagnosis will help "anamnesis" (the history of the occurrence of a malfunction) and the accompanying "clinic".

Narrowing the search

First of all, you should find out what events preceded the current situation. For example:

• The computer began to turn off after a power surge. The probable cause is the failure of the power supply, sometimes along with other equipment connected to it.
• The problem arose during a thunderstorm after a lightning strike somewhere nearby. The reason is electrical damage to the network controller of the motherboard.

• PC stopped working after dusting or replacing/connecting new hardware. Possible reasons are incomplete or incorrect installation of devices in the sockets, bent legs of the processor (if you removed it from the socket), incorrect installation of the cooling system, an unconnected cooler.
• You updated the BIOS before the problem occurred, but did not complete the update (computer restarted, turned off, etc.). The culprit of the problem is a flashed BIOS firmware.

Let's take a look at the side effects next. For example:

• When you try to turn on the computer, there is a smell of burning, smoke appears, the machine knocks out in the electrical panel. Most likely the power supply has failed.
• The computer spontaneously turned off with a loud bang. An electrolytic capacitor exploded on any of the devices inside the system unit.
• When you turn on the PC, the cooler makes 1-2 turns and stops. There is a short circuit in the devices, incorrect or incomplete installation of equipment in the connectors.
• Cyclic reboot immediately after turning on (the cooler makes 1-2 turns, stops, then starts again, etc., repeating the cycle of turning on and off endlessly). Apparently, the BIOS firmware has flown.

The system speaker (buzzer) can give valuable information about the source of the failure if it is soldered on the motherboard or connected to it separately. Sometimes in such cases he manages to file sound signal, which points to the culprit.

Probable cause found. What to do next?

If the above diagnostic steps led you to think about a malfunction or problems with the installation (connection) specific device, the next step is to confirm this version. As you might guess, it consists in revising the connections - inspecting cables, connectors and sockets, checking the reliability of holding the device in the connector, test installation in another slot, etc. And if a breakdown is suspected, replacing the device with a known working analogue.

The following speaks in favor of connection defects:

• Darkening and melting of plastic connection elements (slots, connectors).
• Bent, shorted, broken contacts.
• Visible cracks and creases in cables.
• Contact is broken when you touch the device or vice versa - the computer works while you hold the connected connector or device with your hands, and when you release it, it immediately turns off.

Device malfunction is indicated by:

• Visible defects of the elements - chips, burnouts, swollen, bursting, leaking, electrolytic capacitors rusted at the base, etc.

• Local change in the color of the textolite (usually appears on the reverse side of the board under the faulty component), soot.
• Fast and noticeable heating of any element on the device board when the power is connected. In some cases, faulty components heat up even in standby mode - until the power button on the system unit is pressed.
• Visible dysfunction. For example, the hard drive does not spin up, but makes a rattle or knock, the cooler rotates intermittently or does not rotate at all, etc.
• After the physical disconnection of a suspicious device, the computer stops spontaneously shutting down.

At least one of the listed signs testifies in favor of a malfunction. At the same time, their absence in no way suggests otherwise. Very often, damaged devices do not have defects visible to the eye.

If the power supply turned out to be faulty, do not try to test it by connecting it to normally operating equipment, this will most likely disable the latter.

Also, do not try to disassemble the power supply. Accidental touching of the high-voltage parts may result in electric shock even when the device is disconnected from the mains.

No culprit found, no suspects

Often, failures like ours occur spontaneously - without visible reasons and against the background of normal computer operation. The user has no suspicions about the failure of a particular device. More precisely, all iron is under suspicion. What to do in such a situation?

Let's start simple. Without opening the PC case, unplug it from the outlet or press the power button on the power supply.

Next click power button(turn on) the system unit and hold it for 20-30 seconds. After that, connect the power and try to start the PC as usual. If the problem is caused by static buildup or residual capacitor charge, the next start will be normal and the failure will not affect the further work computer.

If this measure fails, . There is a separate article on this topic, so we will not delve into the details of how to do this. To reset, use the Clear_CMOS jumper or a coin cell battery, which is usually located near the jumper.

Perform further steps one by one, moving on to the next one, if the previous one did not help. After each manipulation, try to turn on the PC.

• Disconnect all peripheral equipment from the computer, leaving only the keyboard and monitor.
• Visually inspect all internal devices and communications of the system unit without disconnecting anything yet. Make sure the connections are secure and tight.
• Observe the behavior of the CPU cooler and case fans when you press the power button. A jerk and stop, as mentioned above, is a typical symptom of a short circuit. Cyclic spin-ups and stops most often indicate a BIOS rally. Complete absence of rotation - problems on the 12 V power line, failure of the fan itself or a failure in the control of the cooling system.

If the probable cause of the malfunction is a failure. Many modern motherboards allow you to do this without a programmer.

If the probable cause is a short circuit:

• Disconnect all hardware from the motherboard that is not necessary to turn on the computer. Leave the processor, cooling system, memory (one module is enough), video, keyboard and power supply connected. If the problem persists, the culprit is among the remaining devices.
• Check . In the event of a short circuit in the load (powered equipment), the switching power supplies are switched off in an emergency. In this way they protect themselves from overload, which is caused by excessive current consumption.
• After finding out that the power supply is working, remove all remaining hardware from the PC case. This must be done for two reasons: to prevent the motherboard from shorting to the case (occurs when the system unit is assembled incorrectly) and to inspect devices from all sides in good light.

• Inspect the equipment for defects as described above. If there are obvious signs of damage, replace the problem device with a compatible analogue.
• Assemble a stand of devices on the table, connect the power supply and check for hot elements on the motherboard and video card. If so, you have found a problem node. If not, start the stand by closing the contacts of the power switch on the "mother". Where exactly they are located on your model can be found in the description for it.

Further troubleshooting of a computer that turns on and immediately turns off, it remains to continue alternately replacing the remaining hardware, in particular, memory and video strips. Although, if you have reached this stage, the most likely culprit is the motherboard. You can, of course, not stop there and move on to diagnosing this particular device, but we agreed to do it with our bare hands. Direct hands plus knowledge - and there are your main assistants in solving any problem with a PC. The rest is secondary.

Reading time: 3 min

This problem is often found on computers, while the system refuses to start. When you press the power button on the computer, it seems to turn on and the fans start to spin, but after one or two seconds they stop. Nothing appears on the screen, of course.

In this article, we will tell you why a computer can behave this way, how you can fix it yourself at home, or at least understand what is wrong.

Possible reasons

First of all, we will check the power supply, you need to make sure that it is in working condition. To check the power supply is the culprit or not, you need to take a known working one and install it.

If you do not have the opportunity to take a working power supply, then you can check yours by closing the contacts you need.

The next step is to inspect the motherboard for swollen capacitors. If there are such capacitors, then most likely the problem is due to them. You can replace them yourself if you know how to use a soldering iron. After replacing the capacitors, the problem should disappear.

Perhaps the cause of all this faulty button turning on the computer. Therefore, try to start the computer by closing the pwr or pwr_sw contacts on the motherboard.

If nothing helped, then proceed as follows. We take out everything from the motherboard RAM, video card, remove cables hard drives, disk drive, usb panel and audio connectors.

It is necessary to leave only the processor and the processor cooler and with this set we try to turn on the computer.

If the computer starts and does not turn off as before, then we install all the removed elements one by one in place. Only you need to install on a completely de-energized computer and you also need to remove it on a turned off computer. Install one element at a time, turn on the computer, and so you will find why the computer does not turn on, and the fans start and turn off. Very often this happens because of the USB front panel and because of the drives.

If replacing the power supply and removing all the elements did not work, then with a high probability we can say that the motherboard has failed.

What to do if when you turn on the computer it does not turn on, but the fans start and turn off?

What should I do if the fans start and stop when I turn on the computer?

This situation is a very common malfunction in which the system unit refuses to start. When you press the power button, the processor fan seems to start spinning, but literally stops after a second. Naturally, there is no image on the screen.

In this article, we will tell you about possible reasons such behavior, as well as what you can try to do on your own at home, in order to try, if not fix, then at least diagnose the breakdown.

Possible reasons

First, in this situation, you need to try on the motherboard. Some boards will not start when the battery is dead.

Replacing the power supply

If it is not possible to temporarily replace the power supply, then although try starting your power supply manually,.

Connection of 4th and 6th pins of the 20-pin PSU connector

Pay attention to the external state of the motherboard, or rather the capacitors on it. Are there any swollen ones among them that can cause such a malfunction.

One reason is a swollen capacitor.

Sometimes there are problems with the power button. Therefore, we recommend trying to start the motherboard by disabling the power button and.

This is what the connected power button looks like

If manual start without a button did not lead to a positive result, then we try to do the following. We remove all RAM, video card from the motherboard, disconnect both cables from the CD drive and hard drive.

Mandatory with USB and audio connectors.

Connecting the front USB inputs to the motherboard

We leave only the processor, processor cooler and power supply connected to the motherboard. Let's try to turn it on.

If the result is positive and mat. the board still started, then we try to alternately install all the removed elements in place in order to identify what is causing the problem. It's not uncommon for a computer to not turn on, fans to start and stop due to problematic CD drives or shorted USBs on the front panel.

In the case when replacing the power supply did not help, as well as removing all attachments from the motherboard, with a probability of 99% we can say that the problem is in the motherboard itself and it needs to be replaced.

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