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This lesson goes on to talk about the maintenance of the charging icon but no charging current when the charger is plugged in

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After the above 6 steps, if there is still no current, go to step 7

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Measure the ground value of the detection pin on the tail socket

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Find the tail plug connector according to the drawing,

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and the mark CC on the connector is the detection pin

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If the ground value is low, first remove the anti-static diode on the line,

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install the motherboard and re-test

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If there is still no current when charging, it is necessary to consider the chip to which the CC pin leads

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Take Huawei Mate 30 as an example

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This is the position of the tail socket, and this is the position of the CC pin

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It leads to the tail socket on one side and the chip U2804 on the other

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If the ground value of the detection pin is abnormal,

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the chip should be removed and re-soldered, or replaced

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Measure the ground value of the CC pin again,

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if there is no obvious abnormality, it is necessary to go to the eighth step

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The eighth step is to measure the ground value of USB data positive and data negative

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The positive and negative of the USB data is marked with USB DPDN on the drawing

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If its ground value is low, it will generally lead to a relatively small charging current, up to 600 mA,

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and the mobile phone can hardly be charged

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Let's take this Huawei mobile phone as an example to see

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This is the location of its tail socket

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This is its data negative, USB DP is data positive

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These two pins are here

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This is the location of the test point

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It can also be measured by the position of the test point

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It is connected to the small component, and through the small component to the chip U2804

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In this circuit, if the ground value is low, we directly replace the chip U2804

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Of course, the anti-static diodes on the line must be excluded first.

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For example, in this line, the USB DP is connected to the diode D2807

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Damage to this diode will also lead to a low ground value, resulting in a relatively small charging current

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There is also a diode on the USB DM, D2806

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We can remove this diode without installing it

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After removing the diode, the ground value is still abnormal,

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we need to replace the chip U2804

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That's all for this lesson