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In this class,

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we will talk about how to repair the fault that the mobile phone can be turned on but does not display

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and what are the steps?

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First of all, when we get a mobile phone,

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we usually first check if the screen is broken

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This can be seen without disassembling the mobile phone

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How can we see if the screen is broken?

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For example, this is a badly broken screen, with tears, or dents

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In this case, there must be something wrong with the screen,

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even if it can be turned on

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Then we need to take a good screen and put it on the mobile phone to test

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There will also be a situation in the actual maintenance,

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the screen has no problem

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I took a good screen to test, it still does not display

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At this time, we need to remove the mainboard,

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and first check the appearance to see if the mainboard is corroded by water

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We focus on the parts related to the display circuits

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If there is water corrosion,

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we will deal with the water corrosion, or re-solder the chip

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If there is no water corrosion, the mainboard is very clean,

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but the mobile phone does not display,

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what should we do at this time?

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We can measure the circuit and measure a working condition in the display circuit

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For example, measure the MIPI bus and measure its ground value on the connector

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We find the connector socket,

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the red test lead is grounded,

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and the black test lead is connected with the MIPI bus

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MIPI lines are pair-to-pair, and each group is connected in series

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In the process leading to the CPU,

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there are two inductors connected in series

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At this time, we can directly find these nearby pins

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If we don't look at the drawings, we directly measure here

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Because, this line generally corresponds to this,

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and there is a ground wire in the middle

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Open a drawing and take a look, such as Xiaomi 9PRO

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We open the bitmap and find the display seat

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There will be a row inductors next to the display seat,

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which are the inductors at the beginning of FL

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This end of the inductor is connected to the socket

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We use the diode gear to measure this

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If there is a ground value, we will ignore it

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If there is no ground value measured,

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at this time, we have to test the end leading to the CPU again

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If there is a ground value on this end,

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it means that there is no connection between here and here

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It can be removed and shorted here with a wire

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This are two line channels,

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we use two lines to short circuit, this fault can be repaired

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Then there may be a situation

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Let's click on this position,

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this section is connected to the CPU U3100

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If we measure the value to be infinite,

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then this phone is complicated to repair

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We need to take the CPU off and re-solder

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Ok, this is how to repair the no display fault due to the problem of MIPI line

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Okay, that's it for this lesson