What's the reason for a cell phone that can't be used?

I can't open the question summary

1. The boot line is not normal: with external power supply, observe the changes in Ammeter, if the ammeter is not responding, is generally the boot line disconnection or the power-on key bad;

2. Battery power supply circuit is not normal: through the battery-powered mode or external interface power supply mode for power supply, in order to distinguish the fault range and determine whether the electronic switch is normal;

3. Power IC is not normal: the control circuit schematic diagram in the power supply IC peripheral circuit test points on the test to see if the test value is normal;

4. System clock and reset is not normal: using a dual-tracer oscilloscope to test the CPU power supply, the way to test the reset, see the measured reset time waveform is correct;

5. Logic circuit is not normal: generally through the repair welding or re welding these chips can solve most of the problems, if still can not boot, should be measured on the periphery circuit and substitution of these chips;

6. Software is not normal: replace the normal code, version or rewrite software.

The cell phone doesn't open in the water.

1, when the mobile phone off the water, whether the boot or shutdown state, the phone should be removed battery.

2, with a hairdryer on the mobile phone and battery constantly blowing, inside and outside to blow, do not let go of any one subtle place.

3. And then, put the cell phone and battery in the sun? Pipit Huan asked Ben Huan?/p>

4, open the phone to see whether the phone is normal. If you can not open or open but there are other circumstances, you should take the phone to repair.

Example

Millet mobile phone can not open the machine how to do

Reason 1, brush machine cause unable to boot to stay in MIUI interface

I believe many friends in the brush machine or other playing machine will encounter millet mobile phone can not boot, has been stuck in the MI interface such a situation
In fact, you don't have to worry! After brushing the machine or cleaning the user data restart takes a long time, about 3-5 minutes, so many users ask this question is not to try to wait.
Brush machine or play other things, clear data and so on restart must not be urgent. Slow down, not the machine problem Oh!!!
Reason 2, long not charge automatic shutdown after the machine can not open

When your cell phone prompts for no power, you do not charge in time, resulting in mobile phone shutdown after the machine (hint: In fact, a lot of posts have said that the millet cell phone battery is limited to trial times, charge and discharge a certain number of times after the battery will be reduced, but advised less frequent rush, do not use the end of the rush)
Most of the reasons for this type of battery caused by the inability to boot, the solution is to buckle the battery with the charger for a few hours after the installation of the battery on the boot look
Try a different battery.
Reason 3, System update upgrade reason can not boot

Many friends find new updates, upgrade the system, and then they can not open the machine
In fact, the best way is decisive brush will be the original system version
How can I brush back the boot? (Try some of the following methods)

1, open the back cover to replace the battery, if there is no second battery suggested to the store to find a shop owner to give you a trial can be turned on, if you can say the battery problem

2, if you will not brush machine can find a brush machine experience, to help you brush back to the original version

3, button down the battery with data cable to connect the mobile phone and computer (Millet mobile phone in the absence of batteries can also be turned on, must be connected to the charger, do not recommend this) try to boot
Reason 4, the mobile phone is flooded, can not open the machine

Mobile phone water can not be turned on, mobile phone intake to look at what the waters, general for the pure, or drink
Pure water, then immediately shut down the machine power, the mobile phone moisture dry, natural air-dry after the boot try
It's not recommended to turn on the phone for a while, it's easy to burn
Drink in, should take things to wipe the phone, as far as possible, the beverage is corrosive, if not wiped out, and so on the phone dry, may have to return to the factory, with water gently wash, dry, not to use fire roast.