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iPhone backlight circuit repairing

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This video mainly explains the iPhone 8P backlight circuit signal search method

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and measurement point search method

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Step 1, open the component map of iPhone 8P,

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find the position number of the backlight power supply

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Step 2, search for the position number of the backlight power supply in the circuit diagram

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Step 3, find the corresponding backlight signals in the circuit diagram

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Step 4, jump to the bitmap according to the pin name to view the connected components

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

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Let's first open the component map, circuit diagram and bitmap of iPhone 8P

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Find the position number of the backlight power supply in the component map

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The iPhone 8P screen is 5.5 inches,

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so there will be two backlight chips in the mainboard

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The search methods of the two backlight chips are the same

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Let's take U5650 as an example to search

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After determining the position number,

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we search for the position number in the schematic diagram

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After finding the backlight chip,

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find the corresponding signal in the schematic diagram

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Let's find the signal 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 U5650 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 sent out by the baseband, and connected to 2 backlight chips at the same time,

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and also connected to the flash chip

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This signal is not easily damaged in actual maintenance

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Let's find the backlight turn-on signal sent by the CPU to the backlight power supply

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when the front camera takes a picture

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In the schematic diagram, the D1 pin of U5650 is the turn-on signal

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sent by the CPU to the backlight chip

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Jump to the bitmap according to the name,

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we can see that the signal is sent to the two backlight chips by the CPU at the same time

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The signal is not easily damaged during the actual maintenance

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Let's find the SW frequency adjustment signal of the boost power supply above the backlight power supply

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In the schematic diagram, the A3 and A4 pins of U5650 are SW2

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This line is specially used to control the L5651 D5651 boost inductor and diode

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When the front camera takes pictures, if the light is relatively dark,

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we turn on the flash function

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When we click the shooting button, this signal will control the diode to turn on and off

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Let the backlight power supply generate a momentary high voltage,

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light up the screen, and use it as a flash

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When we want to measure the quality of this group of boost components,

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we can jump to the bitmap according to the position number to find the location of the component

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During maintenance, L5651 and D5651 are not installed,

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which will not affect the backlight circuit of the display

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In this way, we complete the search for other peripheral signals of the backlight circuit

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Ok, that's all for this video