Causes and solutions for why the mobile phone cannot be turned on: 1. The power-on circuit is abnormal. Use an external power supply to power the mobile phone, and use an electrical connection meter to check if there is any change in the display. If there is no change, it is very serious. It may be that the power-on cable is broken or the power-on button has poor contact. 2. The battery power supply circuit is abnormal: Use an external interface to power the mobile phone and see if it returns to normal when it is turned on. If it is normal, it is determined that the mobile phone's power supply circuit is abnormal. 3. The IC of the mobile phone power supply is abnormal: compare the circuit schematic diagram and conduct a test on the test points of the peripheral circuit of the power supply IC to see if the test value is normal. 4. The system clock and reset of the mobile phone are abnormal: You can use a dual oscilloscope to detect the CPU power supply of the mobile phone and check whether the waveform diagram during reset is correct. 5. There is a problem with the logic circuit: This is a problem with the circuit board of the mobile phone. This problem can generally be solved by repair welding. 6. Software conflict: The installed software is inconsistent with the system of the mobile phone, which may also cause the mobile phone to fail to turn on. You can connect the mobile phone to the computer to delete the program.