iPhone 5S does not boot the ultimate repair

iPhone 5S does not boot 

First, first remove the battery problem, and then check the boot button part.

Measure FL3, DZ1, R22, U25 on the ground resistance, not the normal replacement of the corresponding components.

FL3 and DZ1 feet connected to the ground resistance of 472 ohms.

R22 1 foot resistance of 337 ohms, and U25 5 feet connected to its 2 feet and U25 2 feet connected to the resistance value of 472 ohms.

U25 1 foot is empty, 2 feet resistance is 472 ohms, 3 feet for the ground, 4 feet directly U1 and U7 internal can not be measured, 5 feet resistance of 337 ohms.

Schematic:

The above components on the motherboard position:

Second, if the above are normally press the boot button or not boot, then adjust the power supply test, measure whether the main power supply PP_VCC_MAIN voltage, capacitance C357 can be measured to PP_VCC_MAIN voltage between 3.7-4.2V.

If there is no voltage to remove the short circuit problem, the power supply IC U7 is damaged.

Third, if there is PP_VCC_MAIN main power supply, further measurement of the following groups of voltage:

Press the power button, the normal circumstances can be measured to the following nine groups of power supply:

1, check the schematic diagram, the signal name “PP1V1_CPU” with or without 1.1V voltage, measuring the location to find components L9 \ L10 \ L11 \ L12 inductance or inductance connected with the components. as the picture shows:

If there is no voltage to exclude the capacitor on the circuit short circuit, there is inductance Weld, if not damaged, and finally replace the U7 power management chip.

L9 \ L10 \ L11 \ L12 Location of the inductor:

2, check the schematic diagram, the signal name PP1V0_SOC, with or without 1.0V voltage, measuring the location to find components L15 inductance or inductance connected with the components. as the picture shows:

3, check the schematic diagram, the signal name PP1V8_SDRAM, with or without 1.8V voltage, measuring the location to find components L16 inductors or components connected with this inductance. as the picture shows:

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4, check the schematic diagram, the signal name PP1V2_SDRAM, with or without 1.2V voltage, measuring the location to find components L17 inductance or inductance connected to the components. as the picture shows:

5, check the schematic diagram, the signal name PP1V0_SRAM, with or without 1.0V voltage, measuring the location to find components L18 inductance or inductance connected to the components. as the picture shows:

6, check the schematic diagram, the signal name PP1V8, with or without 1.8V voltage, measuring the location of components to find the capacitor or capacitor connected to this capacitor. as the picture shows:

7, check the schematic diagram, the signal name PP1V8_ALWAYS, with or without 1.8V voltage, measuring the location of components to find C291 capacitor or connected with the capacitor components. as the picture shows:

8, check the schematic diagram, the signal name PP1V2, with or without 1.2V voltage, measuring the location to find components C302 capacitor or capacitor connected with this component. as the picture shows:

9, check the schematic diagram, the signal name PP3V0_NAND, with or without 3.0V voltage, the location of the device to find the component C307 capacitor or connected with the capacitor components. as the picture shows:

If more than one of the nine groups of voltage is not normal, the main check with the connected inductance or capacitor with or without corrosion open circuit.

Fourth, check the clock signal, if all the above nine groups of voltage is normal, began to check the clock circuit, the main measurement element Y1 crystal, or Y1 connected components C36 \ C37 \ R7 \ R71 whether the exception. as the picture shows:

5, check the reset signal, if the clock signal is normal, check the reset circuit, under normal circumstances, the TP10 test point can be measured to 1.8V reset voltage, if not the voltage, check R67 \ U2 \ U3 and other components:

R67 location as shown:

U2, U3 chip position shown in Figure 2.23:

Sixth, the bus will cause failure to not boot

If the power supply, clock, reset are normal, at the test point PP13 \ PP14, can be measured to 1.8V voltage, if not the voltage, check R17 \ R18 and other related components.

I2C bus circuit as shown:

R17, R18 position as shown: