1, caused by incompatibility between software and system.

2. Upgrading the system will lead to.

3. stumbling? Or? Caused by water ingress.

First, ensure 6s first? Is the plus sign dead? Charge the phone for 10 minutes, and press the power to try to turn it on.

Second, if you can't boot, press and hold the power button +home button 10 second until the Apple icon appears and let go.

Third, if there is no response, it proves to be a hardware problem.

Usually stumbling? Or? Water ingress may cause the iPhone screen to be black and the motherboard to be short-circuited: cpu, display ic, power ic, power cord, etc. Because there are tens of thousands of components on the motherboard, as long as a short circuit may lead to failure to boot.

Therefore, testing is needed to determine the short-circuited components. The detection and repair steps are as follows:

1. The ammeter detects whether the current setting of the main board is abnormal. If the abnormality proves that one or several components on the motherboard are short-circuited.

2. The rosin fumigation method is used to detect which components are overheated, and the components with too high temperature will emit a layer of white fog, which is a short-circuit component.

3. After determining the specific short-circuit element, replace the short-circuit element by shifting the value and welding process.

4. Press the power button again to start the test.

If the boot is successful and all functions are tested to be normal, the problem is solved, otherwise there are other short circuits, and the above steps are repeated.