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iPhone display circuit repairing

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This video mainly explains how to find the display circuit signal

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and measurement points of the iPhone XS Max model

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Display circuit diagram query method

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Step 1, find the display connector in the component map,

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and determine the position number of the display connector

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Step 2, search for the position number in the schematic diagram

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Step 3, find the corresponding signal in the circuit diagram according to the pin label

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Step 4, jump to the bitmap according to the pin position in the circuit diagram,

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and find the connected components

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The voltage and diode value can be measured at the yellow points in the bitmap

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Before looking for signals, we first open the iPhone XSmax component map, circuit diagram, and bitmap

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Find the position number of the display connector in the component map,

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and then search for the position number in the schematic diagram

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After finding the display connector in the schematic diagram,

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find the corresponding signals

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Let's first find PP_VDD_MAIN, the main power supply

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In the schematic diagram, pins 35, 36, 2 and 4 of the display connector are PP_VDD_MAIN,

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Jump to the bitmap by the name

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The power supply cannot jump directly to the bitmap,

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because it passes through a connection point

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After connection points XW5784 and XW5785, it becomes the main power supply name

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Jump to the bitmap by the name

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The power supply will not be damaged during actual maintenance,

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because after the power supply is damaged, it will cause a short circuit fault

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Let's find the 1.8V power supply

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In the schematic diagram, pin 1 is the 1.8V power supply of the display connector

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Jump to the bitmap according to the name,

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the 1.8V power supply will be connected to the main power supply through the fuse inductor FL5780

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When repairing the display faults, if there is no 1.8V power supply,

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it is most likely because the inductor FL5780 is damaged

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Let's find the 3V and 1V power supplies output by the main power supply

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In the schematic diagram, the 8th pin is the 3V power supply for the display

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Jump to the bitmap according to the name,

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the power supply will be connected to the main power supply through the inductor FL5783

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In the schematic diagram, the 12th pin is the 1V power supply for the display

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Jump to the bitmap according to the name,

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the power supply will be connected to the main power supply through the inductor FL5782

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These two power supplies are less likely to be damaged in actual maintenance

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If there is no voltage, it is most likely because the fuse inductor is damaged

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Let's find the 1.1V power supply and conversion tube

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The 14 pin of the display connector is 1.1V power supply

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Jump to the bitmap according to the name,

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the power supply is connected to U5701 after passing through the fuse inductor FL5781

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If the U5701 is falsely soldered or damaged, there will be no 1.1V power supply,

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which will cause the assembly screen to be displayed,

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but the original screen will not be displayed

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When we repair, it can be shorted with 1V power supply,

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or shorted with 1.2V power supply

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Let's find the reset signal sent by the CPU to the display

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In the schematic diagram, the 5th pin is the reset signal

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Jump to the bitmap according to the name,

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the reset signal is connected to the main power supply after passing through the fuse inductor FL5700

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Let's look for the ready signal

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Pin 20 of the display connector is the ready signal,

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and the ready signal and the synchronous signal belong to the same signal

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Jump to the bitmap according to the name,

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the signal is connected to the CPU after passing through the fuse resistor R5702

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Let's find the interrupt signal

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In the schematic diagram, pin 16 of the display connector is an interrupt signal,

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Jump to the bitmap according to the name,

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and the interrupt signal is connected to the CPU after passing through the fuse resistor R5704

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Let's find the MIPI bus

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In the schematic diagram, pins 19, 21, 25, 27, 31, 33, 26, 28, 32, and 34

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of the display connector are all marked with MIPI

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These lines are all MIPI buses

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The MIPI bus will be connected to the CPU through an inductor

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Jump to the bitmap according to the name, we can see that

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there are 5 composite inductors on the edge of the display connector

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They are L5720, L5740, L5730, L5710, and L5700

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Among these composite inductors, pins 1 and 4 are an inductor,

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pins 2 and 3 are an inductor, and there is no relationship between them

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One end of the composite inductor close to the display connector is connected to the display connector,

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and the other end is connected to the CPU

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There is a damaged inductor on the MIPI bus, which will cause no display

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Now let's find other detection signals

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PANICB is a signal for the main power supply to monitor the display screen,

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the 9th pin of the display connector is the PANICB signal

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Jump to the bitmap according to the name,

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the signal is connected to the main power supply after passing through the fuse resistor R5701

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Let's find the ADCMUX signal

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In the schematic diagram, the 3rd pin of the display connector is the AMUX signal

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Jump to the bitmap according to the signal name,

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the signal is connected to the main power supply after passing through the fuse inductor FL5703

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Let's find the PANEL_ID identification signal

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The 7th pin of the display connector is the ID identification signal

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Jump to the bitmap according to the name,

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the signal is connected to the CPU after passing through the fuse resistor R5705

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We have completed the search for the relevant signals for the display circuit

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The NC marked in the schematic diagram means that it is an unused pin,

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we don't need to look for it

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During the maintenance, if we measure which pin is abnormal,

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replace or remove the components connected to the pin

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Ok, that's all for this video