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

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In another case, if there is no problem with the capacitor,

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we should also pay attention to the chip during the investigation

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Let's get the mainboard and take a look at the chips that the main power supply leads to

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For example, Xiaomi 10, these chips, and these chips

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We focus on observing whether there is corrosion and there is water ingress

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Like this chip in this mainboard

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If the main power supply has lead to it,

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when we find that the chip is seriously corroded by water, like this,

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we must remove it

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That is, when we see chips that are seriously corroded by water,

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we also remove them one by one

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We take off a chip and measure the ground value of the main power supply line

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If it recovers to more than 200,

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it proves that it was the chip that got water ingress and a short circuit occurred,

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which caused the power connection protection failure

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We take off a chip and measure the ground value of the main power supply line

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If it is still shorted to ground,

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it means that the chip we suspect is fine

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At this time, we will continue to find other chips that are corroded by water

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until the line of the main power supply is no longer short-circuited

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When we remove a chip that is seriously corroded by water,

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the main power supply is no longer short-circuited,

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what should we do at this time?

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We re-solder the chip,

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which is to remove the residue on the surface of the chip,

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and reball it, and then install it

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If there is no short circuit,

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it means that the short circuit is caused by the residue after water corrosion

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In another case, if we re-solder the chip,

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the circuit is still shorted  

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which means that the chip is damaged,

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then we have to replace the chip

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Here's how to exclude one by one

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If the chip is not corroded by water,

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it has not been repaired,

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but the mainboard has been heavily dropped

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The mainboard that is seriously dropped will be deformed

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The mainboard itself is a flat surface,

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and it becomes bent after being dropped

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We need to observe the chip at the bend,

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whether there is a main power supply line leading to this chip

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If there is, we take off the chip at the deformed position

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and measure the ground value of the main power supply line

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to see if the main power supply is short-circuited

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If it is not  shorted anymore,

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we're going to replace the chip,

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and installing a good chip will fix the fault

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If we remove the chip and measure the ground value,

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and it is still shorted,

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we will continue to find the chip in the deformed position

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The chip connected to the main power supply is the chip we are looking for

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Continue to check whether the next chip is broken

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Because when it falls, the mainboard is stressed,

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and the chip is damaged by force

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Ok, that's it for this lesson