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iPhone backlight circuit repairing

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This video mainly explains how to find backlight circuit signals and measurement points for iPhone XR models

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Step 1, open the iPhone XR component map,

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and find the location of the backlight power supply

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Step 2, determine the position number of the backlight power supply in the bitmap

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Step 3, go to the circuit diagram to search for the position number of the backlight power supply,

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and find the corresponding signal

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Step 4, jump to the bitmap according to the pin identification

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We can view the connected components and measure the voltage

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or diode value at the position of the yellow points in the bitmap

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First open the component map, circuit diagram and bitmap of the iPhone XR

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Find the backlight power supply in the component map

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The backlight power supply of the iPhone XR has no logo,

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These two chips are its backlight power chips

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we can determine the position number of the backlight chip according to the bitmap

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The search methods of these two backlight chips are the same

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Let's take U5660 as an example to search

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Enter U5660 in the schematic diagram and click Search

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After finding the backlight chip, find the corresponding signal

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Let's find out the signals that other circuits need to use the backlight power supply

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Let's first look for the incoming call flashing signal from the baseband to the backlight power supply

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In the schematic diagram, the D2 pin of U5660 is the incoming call flashing signal

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from the baseband to the backlight power supply

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

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the signal is directly connected to the baseband by the backlight power supply,

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and connected to the flash chip

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In actual maintenance, the probability of signal damage is relatively small

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Next, let's look for the backlight flashing start signal from the CPU to the backlight power supply

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In the schematic diagram, the D1 pin of U5660 is the incoming call flashing signal sent by the CPU

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Jump to the bitmap according to the name,

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we can see that the signal reaches two backlight chips at the same time

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The signal is less likely to be damaged during actual maintenance

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Next, let's find the circuit of the boost inductor and diode above the backlight power control

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This line is mainly used as a flashing when taking pictures with the front camera

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In the schematic diagram, A3 and A4 pins of U5660 are SW2 frequency adjustment pins

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It is mainly used to control L5661 and D5661,

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let them generate instantaneous high voltage,

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and supply power for the backlight screen

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Used as a flash when taking pictures with the front camera

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When we are measuring the L5661,

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we can jump to the bitmap according to the position number

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After finding the inductor,

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measure the two ends of the inductor to judge whether the inductor is good or bad

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When judging whether the diode is good or bad,

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we can jump to the bitmap according to the position numbe

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If the diode is inconvenient to measure,

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we can measure the components connected at both ends of the diode

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The boost inductor and diode of the backlight circuit of the front camera will not be installed after removal,

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and will not affect the backlight of the display

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Ok, that's it for this video