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We're going to talk about the maintenance for no display faults

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As we learned earlier, if the ground value of the screen power supply is no problem,

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we must consider replacing the display chip

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If the display chip is replaced,

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the screen still does not display, what should we do?

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At this time, we have to take a closer look to test

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whether the enable pin of the display chip is connected to the display connector

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Measure the ground value of the enable pin,

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we can measure whether it is connected

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If the display chip is removed,

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how to judge whether it is connected?

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We're going to measure the connection

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The concept of measuring connection is like this

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This is the display chip, this is the socket

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Assuming this point of the chip is the enable signal,

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it leads to the socket

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If the chip is removed, this is the pad,

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only the pad is left, no chip

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A test lead is placed on this pin of the socket,

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a test lead is placed on the pad, and the connection is measured

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If the measured value is 0,

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it means that there is no problem with the line,

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that is to say, the line is connected

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this is a method

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We must pay attention,

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sometimes when we actually repair, we need to do this

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The description of this enable signal in the drawing is EN,

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EN means enable, which means open

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Including here, there is also an enable signal, EL_ON2

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We need to see whether the enable signal comes from the display chip or another chip

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We're going to measure its connection, and its ground value

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Let's take Xiaomi 11 as an example to see its enable signal

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We find the circuit diagram,

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in which we can quickly see the power supply and signals on the display circuit,

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which is more convenient

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For example, EL_ON2 here is the enable signal of ELVDD and ELVSS

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There is also an enable signal below, 7.6 V

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They are all from G6503

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Of course, the G6503 seat is the display seat

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The display connector itself cannot send out power supply or signal,

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so who is the initiator of this signal?

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It is the screen

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These two enable signals are for the power supply chip to the screen

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If the chip is not removed,

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the screen power supply chip is soldered on the mainboard,

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and we can measure the ground value

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If the ground value is normal,

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it means that there is no problem with the circuit

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Find pins 35 and 37 and measure their ground values

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If the screen power supply chip is removed,

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there is no way to measure the ground value, what should we do?

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As I said just now, find pin 35 from here,

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and then find the pad of the chip it is connected to

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Use a multimeter to measure the connection between these two points

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The red pen is placed on pin 35,

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and the black pen is placed on the pad of the chip

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If it measures 0

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it proves that these two points are connected and there is no problem with the line

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It is also possible to exchange the pens,

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the black pen is placed on the 35th pin,

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and the red pen is placed on the pad of the chip

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If the measured value is 0,

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it proves that there is no problem with the line

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If it shows OL,

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it proves that there is a disconnection in the line

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We need flying wires,

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or see if there is a 0 ohm resistor in series in the middle,

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maybe there is a problem with the 0 ohm resistor

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Okay, that's all for this lesson