First, [fault analysis] : First, the inside of the machine is likely to have poor circuit contact or loose plug-ins, and poor battery contact, and so on. The second is the motherboard problem. So check the above questions together
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①, first open the back cover of the phone, and visually check the plug-ins, batteries, etc., on the entire circuit board, and the patch components on the circuit board, whether there are poor contact or welding places.
②, if the above check does not have the above situation, then the problem has to be measured on the motherboard circuit, first of all to measure the motherboard on all the low-voltage differential voltage regulator chip output pin to the ground voltage is normal, if normal, then measure the main control chip on the motherboard, the pin to the ground voltage is normal, if there is an anomaly, check the chip around the abnormal foot components.
③, to the above fault is best to go to the mobile phone repair shop to let them help you deal with it will be better.