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High current occurs when iPhone starts up

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In this lesson, we will learn about the maintenance process

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Maintenance process Step 3

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If we don't have a thermal imager, we need to repair it the usual way

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We can start with the easiest way

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After the boot, we touch the mainboard with our hands

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to determine whether the mainboard has hot components

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If the mainboard is hot, we can smoke the rosin in the hot position,

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and then trigger the boot to see if the rosin on the component has melted

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If it melts, it means the component is probably damaged

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and we need to replace or remove it

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So let me demonstrate

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Let's take the iPhone 12 mainboard for example

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When we connected the power line, we triggered the switch,

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and then there was a large current

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At this time, we can first use the hand to touch,

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see whether there are hot positions on the mainboard

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When the current is relatively large, we touch quickly,

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do not press hard on it, otherwise it will easily burn the hand

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When we find the hot spot, we smoke the rosin in the hot spot

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This mainboard, we felt the hard drive was hot, we smoked rosin on the hard drive

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After the rosin is smoked, the power is turned on,

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and the rosin on the component is melted, where the rosin is melted, which component is damaged

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As you can see, the rosin on this capacitor has melted

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When the rosin melts, it means the capacitor is probably damaged

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We'll remove it and measure it

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After we remove the damaged capacitor, trigger the switch

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We can see the current jump returning to normal

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Maintenance precautions

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If the mainboard we are repairing is instantaneously high current protected,

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we can skip this step

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Because the power supply protection, the current will not continue,

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the components on the mainboard will not be hot

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So we'll skip this step and use the repair process below

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If we touch the mainboard, only find that the power supply is hot,

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we do not go to remove or replace the power chip

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The power supply chip converts the power supply from the battery to the rear pole components

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When the rear pole component has a short circuit,

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the power supply will be hot first

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So, that's all for this lesson