It so happens that the smartphone does not turn on for no apparent reason. It seemed to work, but then refused. Or the device was in operation for some time, and when trying to use it, it turned out that it was turned off and did not respond to turning it on. There may be many reasons, but quite often you can get by with improvised means and without going to a service center to "revive" an old smartphone.
It is necessary
- - Screwdriver Set;
- - multimeter;
- - USB working wire;
- - power supply (charger).
Instructions
Step 1
The first step to repair is to understand that all actions you do at your own peril and risk. Due to incorrect actions or other factors, the device may "die" completely. Special attention is required to work with the battery and current. The battery must not be swollen, the outer lines must be straight, otherwise it could cause injury and fire. If you have a bad idea of what volts and amperes are, it is recommended to refrain from self-repair.
Step 2
First you need to check the condition of the battery. Most often, the terminals of the external battery are signed with a plus and a minus (otherwise, you should measure it with a multimeter). Switch the multimeter to constant current mode (see the manual for the device) and lean against the terminals, observing the polarity. If the battery charge is less than 3.3-3.4 V (the most common voltage is 3, 7), then there may be a problem in the battery and then go to step 3. If the voltage is higher than 3.3, go to step 4.
Step 3
So, the voltage is lower than 3.3 V. The battery of the old smartphone must be "shaken", ie. apply voltage to it, bypassing all kinds of filters and controllers located on the gadget board. It is they who often do not start up the current on the battery due to the strong discharge. Take the old USB cable, stripped and carefully stripped at one end, plug the other end into the charger and plug into a power outlet. Use a multimeter to determine the “plus” and “minus” at the end of the USB cable (read your multimeter manual for details). After the polarity is established, then you should connect (lean) the wires to the battery terminals with the appropriate polarity. Next, you should wait for the battery to charge, usually 10-13 minutes is enough, the main thing is that the voltage is at least 3, 55-3, 6 V, it should be periodically measured with a multimeter. When the voltage is enough, try putting the battery back in place and turning on the gadget. If the smartphone does not turn on, go to the next step.
Step 4
The voltage is in order, but the smartphone cannot be turned on. It could reach the desired value during the previous charging (which was long before all our actions) or in the process of direct charging from step 3. In the latter case, you should find out what put it below the specified voltage: time or a short circuit on the board. Lean the test leads of the multimeter to the terminals that the battery touches (the multimeter must be switched to "resistance" mode and set to 2000 or a step higher). The battery will help you determine the polarity. If the multimeter showed 0, there is a short circuit on your board, which dropped the battery. It is difficult to do it on your own. If nothing has changed with the contact of the multimeter and the terminals, an open circuit is possible, however, only the service center will help here. If the information from the multimeter differs from that described above, read on.
Step 5
Now you can't do without disassembling the old smartphone. This is necessary for an elementary visual inspection of the board, which could be strongly oxidized, contaminated, which is why it now cannot function properly. After disassembling the device, you should carefully examine the entire board, preferably under a magnifying glass. If there are traces of dirt and oxide, gently clean the board with a toothbrush and isopropyl alcohol (if there is none, you can use a regular one). Be careful, the brush should be soft so as not to damage the elements on the smartphone board. It is advisable to inspect and clean the board on both sides, but it can be difficult for an inexperienced person to remove the board. In this case, cleaning only one side can be dispensed with. Next, we assemble the device, once again check the battery voltage and try to turn it on. If it does not turn on, we try to turn on the device with the charger connected.
Step 6
If after all the previous steps it was not possible to turn on the old smartphone, the problem can be much deeper, in the circuits of the motherboard. It can also be completely flashed firmware or damage to flash memory. In both cases, it is better to take the device to a service center. Although most of the service centers do exactly these described actions, after which they return the device with the verdict “no sense”. If the service has a programmer, good specialists and expensive equipment, they will be able to tell exactly the cost of the repair and revive the old smartphone.
