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How to repair the power adapter

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How to repair the power adapter

Due to the compact structure, large power consumption and high heat generation, notebook computer power adapters have become relatively high failure rates. After these power adapters are damaged, it usually costs tens to hundreds of yuan to buy an original one on the market. For beginners, these power adapters with switching power supply seem to be quite complicated and difficult to maintain.However, the internal circuit design of power adapters for laptops of different brands and models is roughly the same. The working principle is actually not difficult to repair.

How to repair the power adapter is broken

Power adapter repair illustration

1. Tool preparation In fact, the laptop power adapter is not a high-tech product. In fact, the principle of power adapters such as mobile phones and digital cameras is basically the same. As long as people who know some electronic knowledge can repair it. Therefore, we only need multimeters, screwdrivers, welding tools, etc. (see Figure 1).

2. If the external power supply does not supply power during the disassembly process, you can plug in the battery and try. If the machine can start normally, there may be a problem with the power cord or adapter. Then test with a multimeter to find out if there is a problem with the power cord to simplify maintenance. Do not try to open the adapter case at the beginning.
First unplug the octagonal cable from the power adapter (as shown in Figure 2), and first use a multimeter to check whether the octagonal cable of the power adapter is short-circuited; if so, you must replace an octagonal cable. Of course, if the fault persists after replacement, then the power adapter must be disassembled.
There are 4 plastic caps on the power adapter. First buckle it down, then use a screwdriver to remove the screws (see Figure 3), and then open the adapter case. Note that when removing the adapter, try not to damage the case. After the damage, problems such as the strengthening of electromagnetic radiation will occur, affecting the stability of the machine. If the shell breaks, try to repair it.
Open the shell. The first thing we see is the shielding layer (see Figure 4). Carefully remove the shielding layer. Then we can see the internal circuit boards and capacitors and other components. The power adapter is actually no mystery, and there is no difference in principle from ordinary switches and voltage regulator circuits. That is, some capacitors, resistors, inductors, switching diodes, power core chips, etc. (see Figure 5).

3. To find the fault, first check the solder feet with the naked eye, and then check the circuit with a multimeter. If the circuit is intermittent, the contact is generally poor. Check the capacitors, resistors, and inductors for any problems. If the capacitors bulge, it is best to replace them in time to avoid hidden dangers. Use a multimeter to test the protection circuit and rectifier circuit. Figure 6 is the protection circuit. The rectifier circuit is a filter circuit composed of an inductor and a capacitor, and then enters a switch tube circuit composed of a transistor (see Figure 7).
During the test, the author found that the resistance pin was soldered (as shown in Figure 8), then repaired it with a welding tool, reinstalled the power adapter, and turned on the test.
It should be noted that if you encounter a problem with a capacitor during the test, you can buy a capacitor of the same model and capacity (the price is about 5 yuan), then solder the capacitor in question and solder the new capacitor up Just fine.
If you find a problem with the IC power chip, you can follow the same method. Of course, because the IC chip is definitely one of the most important electronic components in the power adapter, and the circuit is too complicated, I found a circuit diagram inside the power adapter (as shown in Figure 9), and found the fault according to the circuit diagram, which can easily solve the problem. .
In use, since the current notebook power adapter has a power of about 65 W, the heat generated internally is mainly dissipated through the plastic shell. The surface temperature of the power adapter is still quite high, and it is estimated that the temperature is generally around 80 ° C. Therefore, when you use a laptop, try not to pile things on it, especially flammable materials, otherwise there will be amazing results.

4.Finally, in addition to the usual maintenance, when buying a laptop or purchasing a power adapter separately, you need to pay attention to the quality of the power adapter. Never buy a sub-charged product. The strong quality and kindness to use will be A very good ending. As for the maintenance of the power adapter, you can usually read more information in these areas. If your electronics level is limited, especially when soldering the circuit, you may ask a knowledgeable friend to help. Of course, during the early warranty period, it is best to send in repair s Choice.


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| Release time: 2019.12.17 Source:
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Dongguan Qiqi Industrial Co., Ltd. specializes in producing: power adapters , chargers, LED drive power supplies, car chargers, switching power supplies, etc ...