If you’re having display problems with your iPhone, then this is a MUST read guide for you.Probably, you could be experiencing any of the following common scenarios:
You don’t have to worry since this is the most comprehensive iPhone display problems solutions guide.Let’s dive right in to see how you can address these problems:
iPhone Display Problems Solutions Example 1:
iPhone 5S backlight brightness adjustment function is abnormal
Failure Phenomenon:
After the phone dropped into water, the automatic brightness adjustment function was normal, but it was not normal when the brightness is adjusted manually. The brightness was adjusted to about 1/5, and the screen brightness was darkest, and the screen brightness becomes brighter when it was set to the lowest level.
Maintenance Processes:
In general, this kind of fault was the backlight circuit problem. It was found that the capacitor C131 was loosened when we checked the working conditions of the backlight driving core. The circuit of the capacitor C131 is shown in Pic 3-46. The position of the capacitor C131 on the motherboard is shown in Pic 3-47.
The circuit of the capacitor C131 Pic 3-46
The position of the capacitor C131 on the motherboard Pic 3-47
The capacitor C131 fell by the multimeter pen’s touch and the solder pad on the power supply end under the capacitor also was dropped off. By checking the bitmap, we noticed that the diode D1 connected to the capacitor C131 was just right next to it, as shown in Pic 3-48.
The C131 connecting circuit in bitmap Pic 3-48
We needed to fly a line from a diode D1 cathode to a capacitor C131 positive, as shown in Pic 3-49.
Connecting C131 and D1 by flying line Pic 3-49
Boot test again and the brightness function was back to normal.
iPhone Display Problems Solutions Example 2:
iPhone 6 powered on with screen off and the screw on the motherboard was missing
iPhone 6 powered on with screen off and the screw on the motherboard was missing
Failure Phenomenon:
The phone powered on with the screen off and the screw next to the motherboard screen line connector was turned off.
Maintenance Processes:
We noticed that the screw BS2503was turned off after we disassembled the phone. The position of the screw that was turned off on the motherboard is shown in Pic 3-50.
The position of the screw that was turned off on the motherboard Pic 3-50
The screw of the defective mother was observed under the microscope. As shown in pic 3-51.
The screw BS2503 Pic 3-51
We found a defective motherboard.Under the microscope, we slowly scraped the PCB under the screw column with the blade and found a line in the lower layer. As shown in Pic 3-52.
The circuit diagram of lines under screw BS2503 Pic 3-52
By comparing with the good motherboard and bitmap, we noticed that this line was the power line of the main power chipset to the LCD screen connector PP1V8_LCD_CONN. Shown as Pic 3-53.
The BS2503 connection wiring diagram Pic 3-53
After soldering the broken circuit with copper wire, then connected to the LCD screen to have the test. And the screen could display as normal. We needed to coat the line with the green oil for insulation protection, and use ultraviolet light to solidify green oil. As shown in Pic 3-54.
The lines with solidified green oil Pic 3-54
iPhone Display Problems Solutions Example 3:
No display suddenly of iPhone 6 Plus in normal use.
Failure Phenomenon:
There was no display suddenly of iPhone 6 Plus in normal use and the chipset of touch power and main power was replaced. Then we tried to power on and power off repeatedly and only one time can start to display, about 1min later the screen off again.
Maintenance Processes:
Based on the customer’s description, we guessed the fault might cause by the missing weld of CPU. Well, this was just judged by experiences, we still had to test all the working condition step by step on repairing. We only received a single motherboard from the customer and we connected it with the testing LCD screen and plugged in the adjustable power supply. The current was above 1A but the screen was still off.
The circuit working condition on the measurement showed that there was no voltage on circuit PP5V7_LCM_AVDDH andPN5V7_SAGE_AVDDN , which was supposed to be±5.7V. The fault of 2 voltages not produced was normally caused by the screen working condition unsatisfied or the communication with CPU is not normal.
After disassembling the LCD screen, then we had to power on and measure the pin 35’s voltage of LCD screen connector J2019, which was 1.8V. There was no problem found on the voltage of pin 24 and pin 26’s I2C bus. The circuit diagram of the screen connector J2019 is shown in Pic 3-55.
The circuit diagram of the screen connector J2019 Pic 3-55
After the power was pulled out, we measured the ground impedance values of the connector, and compared with this value of normal motherboard. Everything was normal. The bitmap of screen connector is shown in Pic 3-56.
The bitmap of screen connector Pic 3-56
After all the above measurement, no problems were found, while the±5.7V was still not generated. So it was very likely that there was something wrong with the CPU or display touch power chipset. First,we measured the pulldown resistance RO702 of the 45 LCM REXT signal, and if there was something wrong with resistance then the CPU and LCD screen ‘s MIPI mode would not work. The circuit diagram of R0702 is shown in Pic 3-57. The position of R0702 in the bitmap is shown in Pic 3-58.
The circuit diagram of R0702 Pic 3-57
The position of R0702 in bitmap Pic 3-58
Connecting one end of the resistance to the ground and the other end to CPU’s pin A7, by measurement the ground impedance values of the CPU end was around 700. There was no trace of missing weld on R0702 after the careful observation. Since the customer had replaced the display touch power chipset before, so we would focus on the troubleshooting of display touch power chipset. The position of display touch power chipset on the motherboard is shown in Pic 3-59.
The position of display touch power chipset on the motherboard Pic 3-59
After removing the touch power chipset, the ground impedance values of the pad of touch power chipset were showed in the normal range. Then we replaced with a good touch power chipset and booted test again. The phone could be powered on with the white screen, but after few seconds the screen was off again. Starting up again after power off, the screen was still off. Is it possible that the main plate layer was heated when we removed the touch power chipset? Then after the motherboard cooling down, it was unable to work normally.
We removed the touch power chipset again and used the cooling fan to blow the motherboard touch power chipset for 10 min. After the complete cooling, we re-measured the ground impedance values and it was found that there was a value for it. But based on the repairing experiences, even the ground impedance is normal, the voltage is not necessarily normal. We plugged in the power immediately and started up the phone, and then we measured the voltage of a few important signals on the touch power chipset pad. We found the abnormal that the voltage of C2 pin of touch power chipset was hopping continuously. C2 pin is RESET_1V8_L, which is the reset signal connected to CPU. The C2 pin of a normal motherboard from a good phone should be a stable with 1.8V instead of a hopping voltage. There was only one possibility that there was something wrong with the motherboard plate layer. The position of RESET_1V8_L in the bitmap is shown on Pic 3-60.
The position of RESET_1V8_L in the bitmap Pic 3-60
The reset signal of display touch power chipset’s C2 pin also connected to the TP2508 next to the hard disk. As shown in Pic 3-61.
The TP2508 test point on the bitmap Pic 3-61
By measurement, the voltage of the TP2508 test point next to the hard disk was in normal range 1.8V but this test point was not connected to the touch power chipset’s C2 pin, from which we were sure that the circuit of plate layer was broken. So we needed to solder a connection line directly from the TP2508 test point to the C2 pin of touch power chipset's pad. After that, we booted test many times and the screen could display as normal. This problem solved.
iPhone Display Problems Solutions Example 4:
The right side of iPhone 6 Plus screen was off while the left side could display normally
Failure Phenomenon:
After the power on, the right side of iPhone 6 Plus screen was off with black color, while the left side could display normally. After the screen off, it was unable to display again when activated.
Maintenance Processes:
This kind of screen fault was caused by the backlight circuit problem. First, we had to repair from the backlight circuit. After the motherboard was disassembled, we noticed that the right side of the backlight was coated with green oil and a line was welded on it, which was from the A1 pin of backlight chipset U1580 to the yellow test point of fingerprint connector J2118. As shown in Pic 3-62.
The position of the flying line connecting on the bitmap Pic 3-62
The I2C bus of the left side backlight chipset U1502 and the right side chipset U1508 was not the same one. The left side is normal while the right side is not, even after the chipset was replaced. So we doubt that there was something wrong with the I2C bus on the right side of backlight chipset U1508. The 2 backlight chipsets on the motherboard are shown in Pic 3-63.
The 2 backlight chipsets on the motherboard Pic 3-6
Checking the stub under the microscope, it was found that on both side of the left and right the screw whole was twisted off. As shown in Pic 3-64.
The screw whole was twisted off Pic 3-6
We scraped the left screw hole with the blade and did not find the broken line while we found the broken line on the right screw hole. As shown in Pic 3-65.
The broken line on the right screw hole Pic 3-65
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