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In this lesson, we talk about the maintenance of trigger small current faults

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Mainly from the following four aspects

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First, the trigger small current faults

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Second, the related circuits of trigger small current faults

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Third, the current of each stage of startup

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Fourth, how to repair the small current faults at startup

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First, let's take a look at the meaning of the word trigger,

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It means when we use the DC power supply to transfer the 4.3V power supply to the battery holder,

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find the power-on signal line on the side of the power-on button base,

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and connect the power-on signal line to the ground wire with a tweezer

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At this time,

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we can see that the current of the DC power supply shows a current response of more than 10 mA

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This means that the mobile phone can be triggered,

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or the trigger has a current response

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This is the DC power supply we use to repair the machine,

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also called the adjustable power supply

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Position A is where the current is displayed

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Let's take a look at the common trigger small current faults

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Let's watch this video, the current jumps 49mA to 150 to 88 to 90mA,

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and then the current doesn't move

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If this current can't continue to go up, it can't boot normally

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Here is the current state of this phone,

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It jumps from 0mA to 49 to 150 to 90mA,

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it cannot be turned on normally

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Let's look at another fault current

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We adjust the voltage of 4.3V to the mainboard

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The current 3mA is a problem with the power cord,

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so don't worry about it here

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We plug the power cord to the battery holder

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This mainboard needs to be pressed,

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we will see the jump of this current after triggering

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Well, let's release the power button,

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we can see that it has been set at around 152mA,

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and finally settled at 156mA

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After we plug this machine into the computer and install the MTK driver,

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it will display this port mode

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Its current state is 0 to 116 to 128 to 156 to 162mA and back to 156mA,

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and finally the current is fixed

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Its current does not exceed 200

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This is also called trigger small current

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It cannot boot normally

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Let's look at another fault

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We set the DC power supply to 4.2V and the current is 0mA

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We buckle the power cord and supply power to the mainboard battery holder,

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its current is still 0mA,

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indicating that the standby of this mobile phone is normal

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Let's take a look at its current, the current jumps faster

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From 37mA to 78 to 36 to 14 and to 36 to 37

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The current cannot be loaded normally

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The description of its current is 0 to about 37 to 78 to 36 and then 0 again,

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And it will not automatically load again

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This is a trigger small current fault

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Okay, that's it for this lesson