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In this lesson, we talk about how to maintain the power connection protection

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We have learned the current phenomenon of power connection protection

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The current jumps quickly between 0-3-0-6-0-4-0mA

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This phenomenon is called power connection protection

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Let's take a look at how to repair it

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As we mentioned earlier,

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the power connection protection is caused by the short circuit on the main power supply

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We opened the curcuit diagarm of Xiaomi 10,

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and we also talked about how to find the main power supply in the drawing

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The code name of Xiaomi's main power supply is VPH_PWR

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We can directly search for the bitmap signal in the bitmap,

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and wen can see its specific line

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It can be said that when the bitmap is enlarged,

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we will see that the VPH_PWR line corresponds

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to the position of the components on the mainboard

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So in the actual maintenance,

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how should we maintain the power connection protection?

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We generally focus on two aspects

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The first is to check the appearance first,

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remove the mainboard from the phone,

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and first check the overall appearance of the mainboard

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to see if there is any problem

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We need to see if this mainboard has been repaired by maintenance personnel or customers,

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or has been disassembled by customers themselves

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If the chip on this mainboard has been repaired and

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the main power supply is connected to this chip,

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then we have to re-solder or replace the chip

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In terms of appearance, where else do we check?

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We need to see if the mainboard is corroded by water

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We can ask the customer, or we can observe it under the microscope,

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whether the mainboard is corroded by water

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If there is serious corrosion, such as capacitors,

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we first remove the capacitors,

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then measure the main power supply line,

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and use the diode gear of the multimeter to measure

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the ground impedance to see if there is a short circuit

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If the impedance to ground recovers to more than 200,

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it proves that we have found the cause of the fault

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It is this capacitor corrosion that leads to the short circuit of the main power supply,

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which leads to the power connection protection

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At this time, we can ignore this capacitor,

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because this is a filter capacitor,

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As we mentioned earlier,

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we only need to ensure that there are 3 filter capacitors on this line

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And there are a lot of filter capacitors on this main power supply line,

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so we don't need to care about it

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What should we do if we remove a capacitor and measure the ground impedance of the main power supply line

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and find that it is still a short circuit?

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We have to continue to find the capacitors that are corroded by water,

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that is, remove them one by one until we find the capacitors

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that cause the power connection protection

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Corrosion in the capacitor may cause a short circuit in the main power supply line

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Ok, that's it for this lesson