Computer Does Not Turn On After Power Off

If the computer does not turn on, this does not mean that something in it has necessarily broken down or that a specialist call, opening the case, etc. is required. The computer does not turn on for other reasons. Let us, according to tradition, analyze this point with a few practical examples.

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: bad sectors or trouble blocks, problems with RAM or something else. If your motherboard does not work, then for this case we also have an article on the site.

Here I want to talk about what all these harsh “iron” People sometimes do not see problems as the most elementary and obvious things, and if the computer does not turn on. can do a lot of unnecessary and unnecessary work.

To begin with, we will analyze the most common case when the computer does not turn on, which plunges an ordinary user into a catatonic stupor and forces him to use the power button to no avail, and then call the master 🙂 This happens regularly at our work when there is a sudden power outage.

The master comes, puts one hand in the system unit, does something there and “the car starts”. The user is satisfied and joyfully distributes inexpensive sweets and cookies 🙂

At regular intervals after the light goes out computers do not turn on. Let’s figure out why this is happening. At the time of a sharp voltage drop, the protection of the power supply is activated. The voltage drops quickly, but due to capacitor banks in the unit itself. not fast enough so that the defense does not have time to react.

Note: There are various degrees and types of protection in a high-quality power supply. Here are the most common ones.

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

In this case, the computer does not turn on due to protection against voltage surges. It shuts off the current supply through the power lines. This occurs by charging a special capacitor of the protection circuit, which, when the accumulated charge does not allow the system to turn on. To enable the system, all we need to do is. remove the power supply cable (220 V) from the power supply unit for 3-5 seconds and insert it back (we will discharge the corresponding capacitor).

Thus, we “reset” PSU protection and it can work further.

This is what is called. “classics of the genre” 🙂 Now I would like to talk with you about more atypical cases when the computer does not turn on. In my practice, they met several times and I considered that this was quite enough to tell about such an opportunity.

So, let’s begin “session of memories” 🙂 On one of the working office machines, a USB mouse was installed with this adapter on the PS / 2 port:

Apparently this same adapter, over time, began to cause a local short circuit (short circuit) in the connector, which automatically led to the operation of the corresponding protection circuit of the power supply. As a result. the computer did not turn on, did not turn on in principle Who and why connected the mouse precisely through the adapter. it’s not clear, but after connecting the device directly to the USB connector everything worked fine.

So that. keep in mind.

Another example: the management department is calling. “Computer does not start“. I’m coming. really does not start. I try a couple of standard options, which I usually sort out on the spot. No result. I take the system unit to us in the IT department at “Debriefing” 🙂 I take it only myself “box” (without cables, keyboard and mouse). I bring it to myself, connect the cables and input devices. everything works!

By the method of tests it was revealed that the reason that the computer did not start was a broken 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. The guard from our work brings his home PC, says: the computer does not turn on, I don’t know what is the reason, please look. Why not help a good person, let’s see!

I bring it to my office, pull it out of the box, put it on the table and conduct an initial visual inspection. What do you say? Better to just show a few photos:

What did the man do with the car !? And this is his mysterious phrase: “it doesn’t turn on, I don’t know why. ” 🙂

Here. second photo from a different angle:

Landing an external card and TV tuner in PCI slots:

The motherboard is screwed into the computer case anyhow: personally, I have never seen a metal hexagon screwed into the same hexagon socket instead of the standard threaded screws, but already located at the bottom of the system board 🙂

Computer we of course “repaired” (the bent one was bent back, the board was screwed correctly), and they took an honest word from the guard not to do this anymore! 🙂

What do I want to draw your attention to when citing these examples? Try to consider all possible options during the diagnosis. Think broader, do not focus only on some “standard” list of faults. If the computer does not turn on, disconnect, for starters, all its external peripherals and input devices, what if they are the reason? Well, and if the computer is not yours. take into account the degree of technical adequacy and literacy of its owners? 🙂

I sincerely wish you good luck in this painstaking work!

Below you can watch a on how to clean the PC keyboard: