Why the computer won't turn on - the first step towards finding out the reason

The most common BIOS sound signals:

Award or Award - Phoenix BIOS

• 1 long beep and 3 short beeps – the video card is not found or is not working
• Long repeating signals - RAM not found or not working

AMI Bios (American Megatrends, Inc)

• 2, 3 or 4 short beeps – RAM problem
• 5 short beeps – the processor may be faulty
• 1 long, 3 short beeps – video card malfunction

Phoenix Bios

• 3 very short and 4 short beeps – the video card is faulty
• 2 short beeps and 1 long beep – RAM fault.

Let's identify the main reasons why the computer does not turn on, and we will follow the path of identifying the source of the problem:

1. Problems with 220V power supply
2. The power supply is faulty
3. Battery ran out
4. A lot of dust
5. Power button
6. Motherboard is faulty

Some may say that what is proposed below is unnecessary, but personal experience says otherwise. If your laptop or computer does not turn on, check the cable connections (not only the plug plugged into the socket, but also the connector connected to the system unit), the functionality of the outlet itself, and other things related to the connecting cables (possibly the functionality of the cable itself).

It happens that everything is fine with the outlet, but electricity does not reach the computer due to poor contact of the power cable. You need to try to pull out the power cable from the system unit and insert it back tightly.

Also, most power supplies have an additional ON-OFF switch (usually you can find it on the back of the system unit). Check that it is in the “On” position (Important: do not confuse it with the 127-220 Volt switch, which is usually red and cannot be easily switched with your finger, see photo below).

If, shortly before the problem appeared, you cleaned the computer from dust or installed new equipment, and the computer does not turn on “at all,” i.e. there is no fan noise or power indicator light, check the connection of the power supply to the connectors on the motherboard, as well as the connection of the front panel connectors of the system unit.

The power supply is faulty

If you don’t have a known good power supply at hand, you can try checking the existing one. To do this you will need a voltage tester. You can measure the voltage only if the lights at least light up when you turn on the computer. To do this, take any power connector and measure the voltage: between any black and red wire there should be 5V, and between black and yellow 12V.

If the voltages differ (a deviation of 5-7% is allowed), then definitely look for a new power supply. If it is not under warranty, then you should not bother with its repair.

When some power supplies wear out, the internal protection may “stick”. Try unplugging the power cable and leaving the computer without power for 5-10 minutes, then plug the cable back in and try turning it on. If the computer still does not turn on, and there is no other power supply at hand, let’s go through other points why the computer does not turn on. You will also be interested in Free programs for repairing flash drives and How to identify unknown devices in Windows.

If the computer makes noise when you turn it on, but the monitor does not turn on

One of the most common cases. Some people mistakenly believe that if the computer is humming, the coolers are working, the LEDs (“light bulbs”) on the system unit and keyboard (mouse) are glowing, then the problem is not in the PC, but the computer monitor simply does not turn on. In fact, most often this indicates problems with the computer's power supply, RAM or motherboard.

In the general case (for the average user who does not have additional power supplies, motherboards, RAM cards and voltmeters at hand), you can try the following steps to diagnose the cause of this behavior (before the described actions, turn off the computer from the outlet, and to completely de-energize press and hold the power button for a few seconds):

To summarize, if the computer turns on, the fans work, but there is no image - most often it is not the monitor or even the video card, but the main reasons: RAM and power supply.

Problems with components or cables

Here we need to work by exception. The problem may lie in any components inside the system unit: RAM, video card, hard drive, cables, expansion cards (TV tuner, sound card, external controllers). To begin with, we leave only what is necessary for the initial startup of the computer, and turn off everything else. Those. We leave the processor with a fan, RAM, video card (if not built-in) and keyboard connected to the motherboard (check if its connector is tightly inserted). We try to insert the RAM into another slot or leave only one stick (if there are more of them). If the computer turns on, then connect the hard drive and see if the operating system boots. If yes, then we connect the devices one by one and thus find the culprit. By the way, the faulty device may still work, but the whole problem lies in the cable or cables. Therefore, they must also be taken into account. See also Troubleshooter and How to make your computer boot and shut down faster.

The battery is low

Every motherboard has a small 3V lithium battery. It supports volatile CMOS memory, which stores BIOS settings. On computers that have worked for 3-5 years, or have been in warehouses for a long time, the battery runs out and the settings are lost. This is easy to notice if the time is reset every time you turn on the computer. Sometimes an error occurs at startup and the BIOS asks you to enter it and save the settings. But in some cases, the computer may not turn on at all or turn on only once. Checking the battery is not difficult if you have a voltage tester. If it is not there, then the battery just needs to be replaced. They are sold at any computer store.

Power button

One of the reasons why the computer does not turn on is the “Power” button. If it does not close the contacts well, then it is logical to assume that the computer will not turn on. It's easy to remove a button. To do this, you need to find on the motherboard the place where the wires from the front panel of the case are connected, and find the “Power” connector there. The connector must be pulled out and the two contacts carefully closed with a screwdriver. If the computer still does not turn on, then move on. You will also find useful Tips for setting up and optimizing Windows and How to speed up your system by 50% without third-party programs.

Motherboard is faulty

The last option is the most disappointing. After all, the motherboard will most likely have to be replaced with a new one, and this will cost a pretty penny. I think you’ll want to get a newer board, which means a new processor, and possibly RAM, and then the video card will catch up, followed by the power supply, in short, change the entire computer. Please note that if you change the motherboard to another of the same level, it must have:

• same processor socket (socket)
• required number of RAM slots, and of the same type (DDR, DDR2, DDR3...)
• interface for connecting an existing hard drive (IDE, SATA)
• a sufficient number of expansion slots for existing cards (PCI, PCE-Express)

If the new motherboard has a different set of system logic, you may have to reinstall the operating system.

In fact, there can be many reasons why your computer stopped turning on. We have prepared for you comprehensive material that describes the main reasons why the computer does not turn on, their description and possible actions to correct them.

We hope that this instruction will be useful to you. You can ask all questions in the comments on this page and we will try to answer them. If you cannot identify and fix the problem yourself, you can always contact us for free* diagnostics and computer repair services.

We do not bear any responsibility for any manipulations you have made with the software or hardware of your computer in accordance with these instructions and do not provide guarantees for restoring the computer’s functionality. Remember that this material was prepared by specialists and computer repair work should be carried out by professionals.

The main symptoms of a computer not turning on

This part contains the main, often common symptoms of a computer not turning on, actions and the sequence of their implementation, by taking which you can bring the computer into working condition.

Basic procedure when the computer does not turn on:Check:

• Is there voltage in the socket, connecting, for example, a kettle?
• Is the power cord connecting the power supply and the outlet faulty?
• Is the power button on the power supply turned on?
• Is the computer power button pressed correctly?
• Correct power supply to the computer monitor
• Are the system unit and monitor connected with a connecting cord?
• Open the system unit and conduct a visual inspection
• Correct connection of wires inside the system unit
• Disconnect all peripheral equipment and try turning it on
• Install a new BIOS battery or disable it temporarily
• Disconnect the video card and all other cards from the PCI slots
• Reconnect the RAM sticks one by one
• Leave only the motherboard, processor and power supply

Following these recommended steps may get your computer back into working order. If the above recommendations did not lead to the desired result, then a detailed clarification of the reasons for the computer’s refusal to turn on is required.

Let's look at the main reasons and symptoms why your computer won't turn on.

• No voltage at the socket
  Use a tester to check that the voltage in the outlet is correct or connect some other device to the outlet and check whether it will work from it.
• The power cord is faulty
  It's quite easy to check if your computer's power cord is faulty. You need to measure the correctness of voltage transmission on both sides with a tester or take another power cord, for example, from a monitor.
• The power supply is switched off
  There is a switch on the outside of the power supply. Try switching it to a different position and see if the switch is broken. On most power supplies, this switch should make a mechanical switching sound (click) when switched to another position.
• BIOS battery is low
  Each motherboard has a separate firmware (BIOS) that is supported by a coin cell battery. If this battery is completely discharged, the computer may not turn on in some cases. We recommend replacing the battery with a new one.
• RAM strips have moved
  If there is an external impact on the system unit (shock, movement, vibration), the RAM strips may move and the computer will not turn on. We recommend disconnecting the RAM and trying to turn it on. Then connect the RAM and try to turn it on again.
• The connecting cables are disconnected
  Open the cover of the system unit and visually inspect for any disconnected wires. Check that the wires are securely fastened.
• A component has failed
  Disconnect all additional cards from the motherboard: sound card, TV tuner, video card, Wi-Fi adapters, controllers, etc. Here you need to use the method of elimination - take out one board, try to turn it on, if when you disconnect one board the computer turns on, then that means it’s the problem.
• There is a lot of dust in the computer
  When a lot of dust accumulates in the system unit, this can lead to serious consequences, including failure of all components with the prospect of purchasing a new computer. If there is a lot of dust, then your computer needs cleaning.
• Severe overheating of the processor and/or video card
  The processor can heat up to hundreds of degrees in a few seconds. If the computer does not turn on due to the processor heating up quickly, then you need to replace the thermal paste. Also, dust could get under the processor or it could “move out” (you need to remove the dust and check that the processor is installed correctly in the socket).
• The power button is broken
  If the reason the computer does not turn on is a broken power button, then you can check this quite simply. Open the system unit and identify two wires running from the power button to the motherboard. These two wires will be connected with plastic connectors to the motherboard. Disconnect them and short the two contacts with something metal that allows current to pass through. Remember to take precautions when working with voltage.
• It smelled like something was burning
  If you smell something burning, immediately turn off the power to the computer and call a specialist. Most often, power supplies burn out. If you are confident and sure that the power supply has burned out, buy a new one and connect it.
• The computer beeps and won't turn on
  If a squeak is heard from the depths of the system unit, these are the so-called BIOS sound signals about the state of the computer. But what do they mean? - you ask. You can find information about what this or that signal means on our website in the section on signals and BIOS codes. By decoding the BIOS signal you can understand what the problem is. Detailed information about BIOS beeps and signals.
• Some numbers light up on the motherboard
  If the computer does not turn on, but the motherboard has BIOS status indicators in the form of a digital-alphabetic display, then by using the codes issued by these displays you can find out at what stage the computer stops turning on/booting and, in accordance with this, take certain actions.
• Peripherals are not connected correctly
  There are cases when people, out of ignorance, connect peripheral equipment to the wrong connectors to which it should be connected. Because of this, the computer may not turn on. Disconnect absolutely all external devices (cameras, mice, keyboards, etc.) from the computer and try to start it.
• There are smudges and swelling on the motherboard
  If you measure that some part (capacitor) is swollen on the motherboard or notice strange leaks of an unknown substance, then most likely, at a minimum, you will have to replace the motherboard with a new one.
• All or some fans do not turn on
  Most likely the power supply or motherboard has failed. They need to be repaired or replaced with new ones. We recommend checking the connection of the wires coming from the fans to the motherboard.
• The computer turns on and then turns off immediately
  There are several reasons for this:
  • The power supply has failed and needs to be replaced
  • The processor overheats (the thermal paste needs to be replaced)
  • Motherboard malfunction (repair or replace)
  • Other components are faulty (diagnostics required)
• The lights are on, the coolers are spinning, the computer does not turn on
  Possible options for not turning on the computer in descending order of probability:
  • BIOS settings are lost or the chip is faulty
  • RAM fault
  • Motherboard is faulty
• Everything works, there is sound, but there is no image on the monitor
  Check the connecting cable between the video card and the monitor, this may be the only problem. The second option is that the video card has failed. If the video card is separate, then you can try installing another video card and check. If there is also no signal with the new video card, then the monitor is most likely broken.
• The computer does not turn on and a blue screen appears
  The so-called blue screen of death appears due to problems in the operation of components, their malfunctions, incompatibility, dirt and problems in the operation of the Windows operating system. A blue screen appears and displays an error code by which you can determine the malfunction and, if possible, fix it.
• The computer does not turn on and a black screen appears
  In most cases, a black screen is evidence of a component failure. Often, when the hard drive malfunctions, this very black screen appears, and it also appears when the RAM is not working correctly and a number of system files are missing from the hard drive. In this case, diagnostics are required, as a result of which the cause of the malfunction will become clear.
• The computer keeps rebooting and cannot turn on
  If at some stage of loading the operating system the computer starts to reboot and the whole process repeats all over again, this may be the result of a malfunction in the operating system or a malfunction of the hard drive. You can try to restore the operating system to an earlier date. A hard drive can have two problems - physical and logical. The logical problem can be eliminated using software, while the physical problem can only be eliminated using mechanical repairs. If the hard drive is physically faulty and there is really valuable information on it, then you can restore it, but we do not recommend using such a hard drive later.
• The computer does not boot and some clicking noises are heard
  If you turn on the computer and the operating system does not load and you hear quiet or loud clicks inside the system unit, then the hard drive is most likely broken. As a rule, physically broken hard drives are not used after repair, since the reliability of their operation may be extremely low.
• The computer does not turn on for a long time (boots)
  If the computer still turns on, but the operating system takes a very long time to load, then most likely this may be evidence of logical or physical malfunctions of the hard drive, as well as evidence of a large number of errors in the operation of the operating system. In case of errors in the operation of the OS, software prevention of its operation is required. Sometimes the computer slows down due to overheating of components.

Computer malfunction can manifest itself in different ways. For example, the computer may not respond at all to pressing the power button. This is exactly the situation we will analyze in this material. Here you will learn the main reasons why the computer does not turn on with the power button.

Reason #1: Power problems.

If the computer was working normally, and then suddenly stopped turning on using the power button, then first of all you need to check all possible problems related to the power supply. First, check if the button on the surge protector or extension cord you are using to connect your computer is turned on.

Secondly, check the power button on the computer's power supply. This button is located next to the place where the cable connects to the system unit.

Thirdly, check the cable itself, which goes from the outlet to the system unit. Perhaps it is not tightly connected to the power supply and therefore the computer does not turn on with the power button.

Also, banal damage to the power cable cannot be ruled out. To check this, find another cable of the same type and use it to connect the computer.

Reason No. 2. Problems with the power button.

If you performed some kind of computer maintenance, for example, changed components or cleaned the computer from dust, then you could touch the wire that goes from the motherboard to the power button. And if the wire is disconnected from the motherboard or simply loses contact at the connection point, then you will not be able to turn on the computer using the power button.

To solve this problem you will need the instructions from your motherboard. To find such instructions, enter into any search engine, go to the manufacturer’s website and open the “Support” or “Support” section. Drivers, utilities and instructions for your board will be available here.

The instructions will tell you where the front panel connector (F_PANEL) of your computer is located on your board, and how it is connected correctly. Using this information, you can restore the power button connection and the computer will start to turn on normally.

It is also impossible to rule out a breakdown of the power button itself, which is located on. If it breaks and no longer closes the contacts, the computer will not turn on.

To check this option, try turning on the computer manually by closing the contacts on the motherboard that should go to the power button. If the computer does not turn on even in this case, then this means that the problem is definitely not in the power button.

Reason #3: Faulty power supply.

If you have checked all of the above, but the computer still does not turn on from the power button, then the problem may be in the power supply. The easiest and most reliable way to check the power supply is to replace it with a known working power supply from another computer. If the computer starts to turn on with a different power supply, then this is the reason.

You can also measure the voltages it generates. To do this, the power supply must be disconnected from the computer components and from the power supply; it is also advisable to remove the power supply from the system unit. After this, you need to connect some kind of load to the power supply so that after turning it on it does not work idle. For example, you can connect some old hard drive that you don’t mind losing.

After this, you need to short-circuit the green (PS_ON) and any black wire (GRN, ground) on the 24-pin ATX connector, which goes from the power supply to the motherboard. These wires can be closed by inserting a paperclip or any piece of wire into the connector. Then we simply connect the power supply to the power supply. As a result, the power supply should work and the fan on it should spin.

If the fan is spinning, you can check the voltage on the 24-pin ATX connector. The red and purple wires should read 5 Volts, the yellow wire should read 12 Volts, and the orange wire should read 3.3 Volts. If there are no voltages or they are very different from the standard, then the problem is in the power supply.

If the computer does not turn on, this does not mean that something in it is necessarily broken or that you need to call a specialist, open the case, etc. The computer does not turn on for other reasons. Let's, according to tradition, look at this point using several examples from practice.

I’ll make a reservation right away: everything that will be described below should be considered as the simplest version of the situation when the computer does not turn on. It is very likely that the reason for this may lie in something else:, or something else. If you have, then we also have an article for this case on our website.

Here I want to talk about the fact that behind all these harsh “hardware” problems, people sometimes do not see the most basic and obvious things, and if the computer does not turn on, they can do a lot of unnecessary and unnecessary work.

First, let's look at the most common case when the computer does not turn on, which plunges the average user into a catatonic stupor and forces him to press the “power” button to no avail, and then call the technician :) This happens at our work regularly when there is a sudden power outage.

The master comes, puts one hand behind the system unit, does something there and “the car starts.” The user is happy and happily distributes inexpensive candies and cookies :)

At certain intervals after The lights go out and the computers don't turn on.. Let's figure out why this happens. At the moment of a sharp drop in voltage, the power supply protection is triggered. The voltage drops quickly, but due to the capacitors in the unit itself, it does not drop quickly enough for the protection not to react.

Note: A high-quality power supply has different degrees and types of protection. Here are the most common ones.

• OCP (Over Current Protection): against power surges;
• OVP (Over Voltage Protection): against power surges;
• OPP (Over Power Protection): overload protection, sometimes called OLP;
• OTP (Over Temperature Protection): from overheating;
• UVP (Under Voltage Protection): against low voltage;
• SCP (Short Circuit Protection): against short circuit;

In this case, the computer does not turn on due to the protection against power surges. It turns off the current flow through the power lines. This occurs by charging a special capacitor of the protection circuit, which, when charged, does not allow the system to turn on. In order for the system to turn on, all we need to do is pull out the power supply cable (220 V) from the power supply for 3-5 seconds and plug it back in (we will discharge the corresponding capacitor).

Thus, we “reset” the protection of the power supply and it can continue to work.

This is what they call a “classic of the genre” :) Now I would like to talk to you about more atypical cases when the computer does not turn on. In my practice, they met several times and I thought that this was quite enough to talk about this possibility.

So, let's begin the “memory session” :) On one of the working office machines, a USB mouse was installed with the following adapter to the PS/2 port:

Apparently this same adapter, over time, began to cause a local short circuit (short circuit) in the connector, which automatically triggered the corresponding power supply protection circuit. As a result, the computer did not turn on, it did not turn on at all. It is not clear who and why connected the mouse through the adapter, but after connecting the device directly to the USB connector, everything worked fine.

So - keep that in mind.

Another example: the management department calls - " The computer won't start". I come - it really doesn’t start. I try a couple of them, which I usually sort through on the spot. No result. I take the system unit to our IT department for a “debriefing” :) I only take the “box” itself (without cables, keyboard and mouse) I bring it to my place, connect the cables and input devices - everything works!

Using the trial method, it was revealed that the reason that the computer did not start was a non-working keyboard (more precisely, its microprocessor). The keyboard has been replaced. It happens that when the keyboard is not working, the internal system speaker emits three short beeps in a row.

And here is another case from my practice. A security guard from our work brings his home PC and says: computer won't turn on, I don’t know what the reason is, please look. Why not help a good person, let's see!

I bring it into my office, take it out of the box, put it on the table and do an initial visual inspection. What should I tell you? I'd rather just show you a few photos:

What was the man doing with the car!? And this mysterious phrase of his: " won't turn on, don't know why?..." :)

What do I want to draw your attention to by giving these examples? When diagnosing, try to consider all possible options. Think more broadly, do not focus only on some “standard” list of faults. If the computer does not turn on, first disconnect all its external peripherals and input devices, what if they are the reason? Well, if the computer is not yours, do you take into account the degree of technical adequacy and literacy of its owners? :)

I sincerely wish you good luck in this painstaking task!

So, what should you do if your computer turns off by itself and won't turn on? It is also possible that the computer suddenly turned off and then turned on normally. Let's consider both options.

1. A very high probability of this problem is simple overheating. Most often the central processor heats up, but the north bridge, video card and power supply can also heat up. When a critical temperature is reached, a protective reaction is triggered and the computer shuts down. As a result, the computer turns off and does not turn on for some time until it cools down. It can turn on immediately, but does not work for as long a time as before it was turned off. In this case, you should clean the computer from dust and change the thermal paste on the processor and video card, if necessary.
2. The computer may shut down if there is a small power surge. The cheaper the power supply, the higher this probability will be. I also recommend unwinding the power supply and checking whether everything is in order there and whether there are any swollen faulty capacitors. I would also check the power supply voltage using S&M or similar. If the problem continues, then you will need another fully working power supply to replace yours and test the computer on it. Since there is also a possibility of a power drawdown in the power supply, as a result of the lack of which the computer also turns off. With age, such a loss of power will occur, which is why it is recommended to install a power supply with a small power reserve.
3. Well, at the last stage there remains a problem with your motherboard. When it is faulty, then there may be such a problem as “turning off the computer and then not turning it back on.”

Rate this article