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High current occurs when iPhone starts up

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In this video, we will focus on the repair process step 4

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If we cannot judge the damaged components through the above steps,

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we need to use a multimeter to judge the mainboard short-circuit position

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Measure the diode values of all the power supplies output by the power supply chip

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Which power supply value is 0, it shows that this power supply is short circuited,

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that represents the components connected to this power supply have been damaged

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It could be capacitors or chips

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So let me demonstrate

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We find the power supply according to the power IC power supply search method

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According to the output name of the power supply,

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search for the measuring point in the bitmap

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The yellow dot in the bitmap allows us to measure the secondary volume

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Let's test the first power supply, which has a test spot above the hard disk

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Let's go and measure it

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When measuring the diode value, the multimeter is set to the diode gear,

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the red pen is grounded, and the black pen is measured

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The measured value is 34

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According to the reference value in the bitmap,

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the diode value of this line is only about 35

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Some value is very low. If you are not sure,

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you can refer to the same location of the ID board

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If the measurements are the same, that means it's normal

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A number of 0 means a short circuit

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Let's measure the second power supply

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The power supply has a measuring point on the outside

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The measured value is 9, which is very low

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This also means normal

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When in doubt, we can measure the same ID board to see if the value is correct

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We need to measure the power output of the power supply, about 30 ways

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If the measuring point is inside the shield when we measure,

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we need to remove the shield before measuring

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Ok, now we're going to measure the power supply of BUCK SWITCHES,

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and we're going to measure the power supply of PP1V8_S2

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This power supply is connected by a large number of components,

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we can first measure this pin, the value is more than 270

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The red pen is grounded,

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and the black pen measures this foot position

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We measured that the power supply value was 0,

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which means that PP1V8_S2 power supply short circuit

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A short circuit means that the power supply component is damaged

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It could be capacitors, it could be chips

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Precautions

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The power supply output has more than 30 power supplies,

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and it takes time for us to measure

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We can start by determining if there's a short circuit in the drive's power supply

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We just need to measure the capacitance on the side of the hard drive

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Why test the hard disk power supply first?

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Because the hard disk power supply is easy to damage

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Note 2

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Some of the power supplies have very low ground values

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For example, GPU power supply, its value is very low, only 1 or 2,

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but it does not mean short circuit

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This mainboard is the iPhone X mainboard

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We measured the power supply of the GPU and it was only 3, but it was normal

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The value is already very low

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Some multimeters, the value could be more than 3 when the two pens touch together

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Low value during measurement does not indicate short circuit

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When measuring the multimeter will ring, it does not mean short circuit,

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we must look at the value,

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the value is 0 to represent short circuit

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So that's it for this lesson