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High current occurs when iPhone starts up

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In this lesson, we will focus on the maintenance process step 6

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After the rosin is applied, the switch is triggered,

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if no hot component is found,

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we need to use adjustable power supply to burn the machine

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When the machine is burning,

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the voltage of the adjustable power supply is adjusted to be consistent

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with the voltage of the short-circuit fault point

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For example, when we measure a short circuit in 1.8V power supply,

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we need adjust the adjustable power supply to 1.8V

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If the voltage is too high,

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all the components on the line will be damaged

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When burning, we first clamp the tweezer with the positive pole of the adjustable power supply,

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connect to the short circuit, and then ground the negative pole

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Wait about 10 seconds to see if the rosin on the component has melted

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Where the rosin is melted, it means the component under the rosin is broken,

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including the main power supply

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So let me demonstrate

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First, let's adjust the voltage to the same voltage as the short-circuited fault point

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The fault voltage of short circuit just now is 1.8V,

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so we will adjust it to 1.8V

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The current does not need to be adjusted, the maximum is OK

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We use the red clip of the boot wire to hold the tweezer

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The tip of the tweezer has better be thick,

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because the current of the burning machine is too large,

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the tip of the tweezer is too thin, it is easy to be burnt

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We put the tip of the tweezer into the short circuit

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A short circuit will connect a lot of components,

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so we chose a good short connection location

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Do not choose the corner position,

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because corner position may lead to short circuit,

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the mainboard will be burnt

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After positive pole is connected, the black clamp is connected to the screw post position,

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that is, the ground wire

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After three or four seconds,

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let's see if the rosin on the component has melted

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Where melting is indicative of component damage

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If there is a shield on the component,

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we need to remove the shield and smoke the rosin on the component

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to see if there is any component damage

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The large current of mainboard is generally caused by capacitor damage

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If the current is 300 or 400mA,

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it is usually because the chip is damaged

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So that's all for this lesson