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High current occurs when iPhone starts up

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In this lesson, we will talk about the maintenance process step 7

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When we're taking the burning test, the current of some mainboard is very small,

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only 100- 300mA, burning machine can not judge the fault

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In this case, if we do not have a thermal imager,

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we can only remove the components connected by the short circuit in turn, such as capacitors and chips

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Normally, we remove the capacitor first,

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then we remove the chip

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If we have a thermal imager,

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we can use the thermal imager to determine the damaged component

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First, we fly a wire in the short circuit,

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connected to the positive terminal of the adjustable power supply,

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and the negative terminal of the adjustable power supply is grounded

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Then we put the mainboard under the thermal imager and look at the chip on the mainboard

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Which chip or capacitor heating represents damage,

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we can directly replace it

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Let me show you how to use a thermal imager to determine a fault

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The voltage of the adjustable power supply should be adjusted to the same as that of the short-circuit fault

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In the short circuit line, the wire is connected with the positive pole of the adjustable power supply,

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and the negative pole is grounded

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Then put the mainboard under the thermal imager

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When powered on, the mainboard is observed through a thermal imager

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We find that the temperature in the lower right corner of the mainboard is rising,

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which indicates that the chip in the lower right corner is damaged

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The current of this mainboard after short circuit is relatively large,

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we can quickly observe it

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If the current is low, maybe we need to wait longer

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Ok, that's the end of the process for large startup current