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In this lesson, we talk about the current and maintenance direction of each stage of startup

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When the mobile phone is turned on, the current at each stage is different,

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which means that the circuit state is different

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First, let's take a look at the standby of the phone

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What is standby?

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It is to use the battery to supply power to the main board,

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without pressing the power button,

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the main board supplies power to the charging chip,

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converts it into the main power supply,

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and then supplies it to the power supply chip,

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but at this time, this line has no current,

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which is called the standby circuit

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The current of the standby circuit is 0mA

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After we press the power button,

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we pull down the power button signal

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The power output from the power chip is the power output controlled by the power-on signal

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If it is only the power supply output,

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its current is about 30 mA

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After the power supply works,

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the clock circuit works, and the current will be about 40 mA

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After the reset circuit works, the current is about 60 mA

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That is to say, when we press the power button to supply power,

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the clock is normal, the reset is normal,

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and the current of this mobile phone should be at least about 60 mA

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The CPU starts to work, and the current is generally around 80 mA

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When we see that the current of a mobile phone jumps to 80 mA,

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it means that the CPU has reached a working state

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Of course, 80 mA is the state of an inport mode of the CPU

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The circuit only goes to the CPU

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If the CPU cannot recognize the hard disk,

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it will only load its own written program,

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which is called the inport mode

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Let's take a look at what is inport mode

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If a mobile phone does not recognize the hard disk and the current is around 80 or 100 mA,

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we can connect the mobile phone to the computer,

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find the device manager in the computer management page of the computer,

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and the inport mode will appear in the device manager

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If it is a Qualcomm platform processor,

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its inport mode is HS-USB 9008,

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Qualcomm is the brand logo,

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and 9008 is the specific sorting port,

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If it is the processor of the Hisilicon platform,

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then it will enter the port mode of HUAWEI USB COM 1.0

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After the CPU works,

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it needs to read the boot program in the hard disk

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At this time, the current of the mobile phone will jump,

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generally higher than 120mA

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and the current will continue to jump between 100 and 300 mA for a period of time,

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this is the loading program

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The display starts to work,

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the current is about 300 mA, and the display will light up

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This is the current at each stage of the phone's startup

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Generally, when we study the current to this stage,

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we have a general direction for maintenance

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In the actual maintenance,

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at which stage are most of the problems of Android phones?

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It is the stage from the start of the CPU to the start of the display,

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and the current is from 100 to 300 mA

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Okay, that's all for this lesson