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iPhone backlight circuit repairing

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This video mainly explains how to find backlight circuit signals

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and measurement points for iPhone 11 models

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Step 1, open the iPhone 11 component map,

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and find the backlight chip in the component map

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Step 2, determine the position number of the backlight chip in the bitmap

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Step 3, go to the schematic diagram to search for the position number of the backlight chip,

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and find the corresponding signals

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Step 4, jump to the bitmap according to the component signal name,

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the voltage and diode value can be measured at the position of the yellow point in the bitmap

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Before looking for the signal, we first open the iPhone 11 component map,

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circuit diagram, and bitmap

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Find the backlight chip in the component map

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Because the display screen of the iPhone 11 model is 6.1 inches,

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there will be 2 backlight chips in the mainboard

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The search methods for the two groups of backlight chips are the same

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Let's take one of them as an example to find

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According to the position of the backlight chip in the component map,

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find the same position in the bitmap

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Let's find out the group of backlight chip U5650

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According to the position number of the backlight chip,

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we search for the backlight chip in the schematic diagram

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After searching for the backlight chip, search according to the signal in the schematic diagram

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Next, let's find the turn-on signal of the baseband to the backlight

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In the schematic diagram,

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the D2 pin of the backlight power supply is the turn-on signal sent by the baseband

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Jump to the bitmap according to the name,

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we can see that the signal is directly connected to the baseband chip

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The voltage and diode value of the signal can be measured

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at the position of the yellow point in the bitmap

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This signal is basically not corrupted in the backlight circuit

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

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In the schematic diagram,

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the D1 pin of the display power supply is the turn-on signal from the CPU to the backlight

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

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This signal will not affect the backlight circuit and is rarely damaged during maintenance

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Next, let's find out the SW frequency adjustment pin of the backlight power supply

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control boost circuit when taking pictures

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

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and this group of signals is dedicated to controlling the front camera

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The boost circuit used by the flash when taking pictures,

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we can find the relevant inductors and diodes according to the circuit name

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L5651, D5651 are the boost inductor and boost diode used by the flash

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This group of inductors and diodes will not be installed after removal,

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and will not affect the backlight circuit

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In this way, we have completed the signal search for the backlight circuit of the iPhone 11

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The search method of another backlight chip U5660 is the same

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Ok, that's it for this lesson