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Small current when iPhone is turned on

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In this video, we will mainly verify the working principle of the small power-on current

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We know that the CPU lacks power supply, clock signal and reset signal,

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which will lead to small current faults

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Let's remove the 24M crystal oscillator first, or disconnect the line,

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and observe the change of current

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Let's take the iPhone X model as an example

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Find the 24M crystal oscillator in the component map,

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and search for its position number in the circuit diagram

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After finding the crystal oscillator,

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we can see that the crystal oscillator pin passes through a resistor R1011,

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and then connects to the CPU

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The other pin is directly connected to the CPU

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After removing the resistor R1011,

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let's turn it on to see if it will cause a small current

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We first find the position of R1011 in the bitmap,

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the resistor is below the crystal oscillator

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Let's take a look at the take-off current of the iPhone X mainboard

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After the switch is triggered, the current starts to jump from 50mA

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Next, after we remove the resistor R1011, look at the start-up current

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After the resistor is removed, we trigger the switch,

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the current is only 24mA, which is half of the normal current,

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which is 50mA normally

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Next, we disconnect or ground the reset of the CPU, and then test it

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We search for COLD_RESET in circuit diagram

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The reset signal of the CPU is connected with other reset signals through a resistor R1020

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Let's take a look at the position of R1020 in the physical object

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It is at the bottom side of the CPU, above the USB chip

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We remove the resistor R1020, and then turn on the power to test the current

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After removal, we trigger the switch,

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the current is only 41mA,

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which is about 10mA less than the normal current

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Through testing, we found that problems with the clock signal and reset signal will cause small current

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If the power supply inductor of the CPU is removed or falsely soldered,

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it may cause a large current

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If you're interested you can test it

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Ok, that's all for this video