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Hello everyone, in this lesson we will talk about the workflow of the VGA interface

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The workflow of the VGA interface is very simple, only 3 steps

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And many devices don't even need the first step

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The first step is to supply 5V power to the screen

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After the 5V power supply is supplied to the screen,

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the main board will read the information of the screen through the serial bus of pins 12 and 15

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After reading the screen information, the next step is to control the display screen

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through the three primary colors of red, green and blue and the line field signal

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At this point, the workflow of the VGA interface is over

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It is very simple

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The working process of the VGA interface is relatively simple,

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so its maintenance process is also relatively simple

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Let's take a look at the repairs that the VGA interface does not display

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Now the VGA interface on the mainboard is generally not supported natively.

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Generally, the DP signal is converted by a DP to VGA chip.

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Therefore, when we repair the VGA without displaying a fault,

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we not only need to check the VGA, but also check the DP to VGA chip.

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Let's briefly talk about the maintenance process

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First of all, it is easy and then difficult, first soft and then hard

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Check for physical damage near the interface

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For example, the pin of the VGA interface is crooked, or a part is dropped near the VGA interface.

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If there is no problem with the appearance, then we will follow the workflow of the VGA interface to overhaul

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First check the power supply of the VGA interface

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The power supply is usually 5V

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After checking the power supply, we have to check the pins 12 and 15 of the VGA interface

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Is its serial bus to ground normal?

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If you have an oscilloscope, you can also use an oscilloscope to measure whether there is a waveform

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If there is a waveform, it means it is normal.

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If pins 12 and 15 are also normal, measure the field signals of pins 13 and 14 to see if their ground values are normal

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If the ground value is normal, it may be that the conversion chip is damaged,

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or its working conditions are not satisfied

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We can check the working conditions of this DP to VGA chip

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Its working conditions are the same as those of the digital interface

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We check the working conditions of the chip according to the working conditions of the digital interface.

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Well, the above are the overhauls that the VGA interface does not display

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Next, let's take a look at the maintenance of VGA color cast

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For example, in the picture on the right, this picture is obviously reddish

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VGA color cast is generally caused by the imbalance of the three primary colors of red,

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green and blue, or the lack of one

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For faults like this color cast, we focus on checking the three primary colors of red, green and blue.

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Still the same, let's check for cosmetic glitches first

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If there is no problem with the appearance, let's check whether the ground values of the red,

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green and blue primary colors are normal

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Pay attention when measuring, generally a 75 ohm pull-down resistor is connected behind these three lines

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We'd better remove the 75 ohm pull-down resistor first when measuring,

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otherwise it may cause misjudgment because of this resistor

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In general, the ground values of the three lines are the same

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After checking the ground value, we check whether the red land, green land, and blue land are normal

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The red, green and blue grounds of most mainboards are directly grounded

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There are a small number of mainboards that are not directly grounded, you need to pay attention

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If the red, green and blue are all normal

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We can only try to replace the DP to VG chip

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Well, the above is the workflow of the VGA interface and the maintenance of the VGA interface