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Small current when iPhone is turned on

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In this lesson, we will learn the maintenance process of small current

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When repairing small current faults,

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we must first check the appearance to see

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if the mainboard has obvious water corrosion or damaged components

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After the elimination, if there is still a small current,

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we will follow the maintenance process to check and repair step by step

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Step 1 of the small current maintenance process,

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measure whether the power supply voltage of the CPU is normal

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There are about 15 power supplies for the CPU, we all need to measure them

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If there is no voltage when we measure,

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it is generally the damage of the inductor or the power IC

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Let's replace the inductor first

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If it is abnormal after replacement, we need to replace the power IC

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Matters needing attention when measuring power supply

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The CPU's GPU power supply and GPU_SDRM power supply cannot be measured when measuring the voltage

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These two power supplies will have voltages when we're playing games on the phone

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Why not measure the CPU power supply resistance value?

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If the power supply of the CPU is short-circuited,

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it will cause a large current,

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and we will not be able to repair the fault of the small current

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Next, let me demonstrate how to measure the power supply of the CPU

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Let's take the iPhone 12 model as an example

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After finding the power supply of the power output, jump to the bitmap

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Let's measure the power supply voltage of this road first,

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the voltage value of this power supply is between 0.5-1.06V

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After the mainboard is powered on,

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the black marker is grounded,

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and the red marker is used to measure

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At this time, the voltage we measured is about 0.7V,

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which is the same as that marked in the drawing,

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indicating that it is normal

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Let's measure the next power supply, PP_GPU power supply

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The voltage cannot be measured after turning on the computer,

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and the voltage will only be available when playing games

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Now let's measure it

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We measure the position of the yellow point,

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the measured voltage is 0V,

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and there is no voltage at the other end

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Just measured the power supply, we can see that it still has voltage

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Next, let's measure the PP_SOC_S1 power supply

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This power supply will also go to the CPU

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Let's measure it on this capacitor,

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and the measured value is 0.7V,

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which means that the power supply of this circuit is also normal

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Let's continue to measure

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PP1V8_S4 does not supply power to the CPU, we do not need to measure

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This power supply does not go to the CPU, and we don't need to measure it

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PP_DISP_S1 supplies power to the CPU,

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and the voltage is 0.75V, indicating that it is also normal

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Let's measure the power supply of PP_SRAM_S1, which is supplied to the CPU

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We measure on the capacitor C1874,

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the voltage is 0.78V, which is also normal

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Next we continue to measure

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PP1V2_S4, this power supply is not supplied to the CPU, we do not need to measure

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PP_AVE_S1, this power supply is for the CPU, let's measure it

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The voltage value is about 0.7V

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Let's measure the power supply of AVE_S1,

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the voltage is 0.7V, which is normal

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For CPU power supplies, we all need to measure one by one

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If the voltage value we measured is different from the voltage value marked in the drawing,

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it means that there is something wrong with the power supply

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Either the voltage is low or the voltage is high

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Generally, there is a problem with the inductor that generates the power supply

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If it is soldered or damaged, we need to replace it

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If the voltage is still abnormal after replacing the inductor,

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we need to replace the power IC

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Ok, that's it for this lesson