top-5 simple reasons for device failure

Short description

A reviewer of flea markets in Spain has shared his hobby of repairing laptops, explaining common breakdowns and how to fix them. 70% of the time, the issue is with the MOSFETs, the two input switches that determine the power supply. A failure in one of the input keys can prevent the device from receiving power, which is a frequent occurrence on ASUS and Lenovo laptops. In addition, the problem could be caused by a short circuit or a malfunctioning ceramic capacitor; nevertheless, it’s possible to apply a voltage to identify the malfunctioning element by dropping isopropyl alcohol on a place that is heated or applying special freezing sprays. Furthermore, the reviewer notes that PCs of devices could fail to turn on due to power button or keyboard problems, issues with the BIOS firmware, or liquids poured on the device’s surface.

top-5 simple reasons for device failure

Hello everybody! I usually post reviews of flea markets in Spain, but today I’m going to talk about something a little different. The fact is that my hobby is repairing laptops. I used to repair iPhones, but then somehow got bored. For some reason, I like laptops more – I buy them at the local Avito analogue, repair them, then either give them to friends or sell them.

Hundreds of laptops have passed through my hands, both with very complex failures and very simple ones. I will not say that I am a master of the highest class, but, for example, I can replace VRAM, a processor or a hub. I mean, of course, those components that are soldered on the board, and not removable. Today I will talk about the most common types of laptop breakdowns, which are quite easy to fix, but many of them put ordinary users at a standstill. If you are a high-class craftsman, you are unlikely to get something for yourself. But if you are a beginner or just a user, I think it will be interesting.

In general, everything I will talk about below is “does not turn on and does not charge”, “the charging LED lights up, but does not turn on” and so on.

Does not turn on and does not charge


Most often, in about 70% of cases, the problem is in the two input switches (MOSFETs). MOSFET is an abbreviation of two English words: Metal-Oxide-Semiconductor (metal – oxide – semiconductor) and Field-Effect-Transistors (transistor controlled by an electric field). They are responsible for ensuring that the meals differ by price. If something happens to one of the input keys, then the board does not receive power, and of course the device cannot turn on or start charging.

So, failure of such a key is a very common phenomenon. Even a novice craftsman can fix this. It is necessary to check the mosfet for breakdown (sometimes it is visible even without a microscope, as in the photo below). And if it “died”, it must be replaced with the same analogue, after which the laptop begins to function normally. In my practice, input keys most often fail on ASUS or Lenovo laptops.

Sometimes, by the way, everything is ok with the input keys, but the current does not go beyond the first or second. This means that something further down the board is wrong. The mosfet tries to “open”, but then there is a short circuit or something else, and it immediately “closes”, not passing the current further. In this case, the repair should be more difficult, but here there are many more options. There may be a “burnt” processor, failed ceramic capacitors, etc.

Repairing a laptop with problematic input keys is a matter of a maximum of half an hour, of which most of the time is spent on disassembling the laptop. Many manufacturers place the input keys on the underside of the board, so it must be removed for repair.

Short circuit on the board

It may also happen that the input keys are useless, but the problem is deeper. Very often it happens that a ceramic capacitor or a group of elements fails. The easiest way is when there is a short circuit through the capacitor. Then the main thing is to find the culprit of the problem, solder it and replace it with a worker (but often you can not change it, it will work anyway). The ways to solve the problem differ among different masters, the easiest way is to apply a voltage to the problematic circuit that corresponds to the characteristics of the circuit (mainly it is 19.5, according to others it can be 5V, 3V, 1.8V, 1V, etc.). In this case, the burned-out element heats up and can be found either by touch, or with a thermal imager, or by dropping isopropyl alcohol on a place that is heated – the alcohol “retreats” from the glowing element, even the smallest, which is very visible. There are also special freezing sprays that turn into frost. Someone uses thermal paper (cheques), but whatever someone uses, it all helps to find the breakdown.

If the processor, video chip, multicontroller or hub heats up, this may indicate their failure, then it is much more difficult to do. But sometimes the problem is not the heating element. Everything is more complicated here, and cannot be explained in one article. In this article, let me remind you, I am talking about simple breakdowns.

It does not turn on, but the charging LED lights up

There are more possible cases of breakdown here than in the previous ones. The problem can be both in the circuit of a power source and with other components.


Since we are talking about simple breakdowns, I will mention the BIOS – a small chip with firmware. The Internet tells us that when the computer is turned on, even before the operating system is loaded, the BIOS is activated, which is responsible for starting the computer, testing computer components, the parameters of these components, and implementing input – output functions.

If you’ve ever updated the bios, you’ve probably seen warnings like “Do not turn off the computer and power until the update process is complete.” It is not for nothing that they warn, oh, not for nothing. If the laptop turns off during the firmware update, then in 99% of cases there will be problems with turning it on. And a normal user will not do anything. There are some models that allow you to update damaged firmware from a flash drive (in HP, for example), but there are few of them. Most often, you need to take a programmer, this is a cheap device that is sold on the street, solder the chip and update the firmware already when connected to a working PC. There are also “clips” that make it possible to connect to the chip on the board without soldering, but I recommend soldering, it’s easier and safer for the board.

In my practice, bios “flys” most often in Acer and Lenovo. Masters have a saying: “In any unclear situation, the bios.” And really, the laptop can behave very strangely, but before you start digging into the components, you should try to flash it – it can solve the problem within half an hour.

By the way, the laptop may try to turn on, the screen backlight flashes, or the logo appears and everything “hangs”, or the laptop goes into a cyclic reboot – all these are most likely problems with the bios.

Keyboard/power button board

Very often, the laptop’s power button simply fails – and in 90% of cases, these are buttons that are located on the general keyboard. I would fine the developers for such a decision, because in this case you have to change the keyboard, which takes a lot of time. For an ordinary user, the problem looks like this – the laptop charges, but does not turn on.

Many times I have bought expensive gaming laptops from online flea markets with a user verdict of trash, where the problem was precisely the power button on the keyboard. It’s getting ridiculous – once I saw a lot, the motherboard of a gaming laptop. Asked the user if he had everything else – he said yes, but he was going to throw it away. I asked him to send everything, assembled it in the workshop, it turned out that the problem was precisely in the button, he fixed it in an hour, probably. I don’t understand why there are so many people who like to throw everything away in Spain at once, because you can sell it at least for spare parts.

Sometimes the loop of a separate power button fails (for example, when the laptop was disassembled to be cleaned at home, and it was pulled strongly, or inserted crookedly, etc.). It also gets better quickly. The main thing is to check whether there is current on the contacts of the button or keyboard and start dancing from there.

Pouring liquids

I will talk here about “slagers” with small areas of charge flooding. If most of the surface of the board is touched, the repair will be difficult and it is not a fact that it will help. But it happens that literally a drop of liquid gets to a place that is critically important for the operation of the device. Well, for example, on the legs of the same bios or microcontroller. Often this does not lead to damage to all other components, just quickly formed oxides close some contacts, and the laptop does not turn on. Often, simple cleaning helps to bring the device to its senses. If the track/components have not yet been affected by corrosion, then cleaning may help. In one of the cases, the drop fell on a tiny microchip that was responsible for forming the image on the screen. The display backlight worked, but there was no image. As a result, cleaning was enough for everything to work. So that there was no corrosion, I first heated the chip with flux (up to 200C, no more), and then soldered the contacts.

In fact, flooding usually leads to complex complex problems that are not easy to solve. But sometimes it happens as I described above.

In general, so far in this article I have told everything I wanted to. The described breakdowns are the cause of failure of approximately 80% of problematic devices. The rest are much more complicated cases.

I repeat, the material is not for professionals – they already know all this. But there are not so many articles that talk about such breakdowns (I don’t mean the format “you need to turn it on, remove the battery, disconnect the adapter, turn it on again”). So I hope Khabru will be interested. If so, then I can publish other cases from my practice that are more specific, complex and interesting for professionals.

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As an example, I just remembered a flooded gaming laptop, where a pair of mosfets burned out, the tracks on the board corroded and there was a short circuit in the interlayer (boards of modern devices are multi-layered, with many contact tracks that connect various components and chips).

Well, that’s it, see you soon!

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