4 steps can fix iPhone 6 Plus LCD no display CPU issue

Received an iPhone 6 Plus need to repair. The iPhone 6 Plus LCD screen has no display and no light, it changed the kit before. Now, we need to solve this problem step by step.

1. Measure the working condition of iPhone LCD display IC, all is normal. Then measure the display socket J2019 with Fluke 15B+ Digital Multimeter, we found the #3 pin is short circuit. 90_AP_TO_LCM_MIPI_DATA3_N MIPI image transfer data bus leads directly to CPU, the initial diagnosis is that the CPU is continuous tin or internal damage.

2. Remove iPhone CPU and then measure this signal line, we found it is the earthing short circuit, which is CPU internal damage, the kit is damaged. 6P and 6 are not the same size; the circuit design is also not the same. By analyzing the WUXINJI schematic diagram, we found the solution.

3. According to the comparison of WUXINJIschematic diagram, we found that iPhone 6 Plus has one more a set of MIPI image transfer data bus than iPhone 6, 90_AP_TO_LCM_MIPI_DATA3_P、90_AP_TO_LCM_MIPI_DATA3_N, and iPhone 6 doesn't have that line. Because the iPhone 6 only needs to display 4.7 inch images, but iPhone 6 Plus needs to display 5.5 inch images.

4. The faulty iPhone 6 Plus is 90_AP_TO_LCM_MIPI_DATA3_N short circuit, we decided to abandon the 5.5 and install the 4.7 directly. Move the CPU on this fault board to iPhone 6 motherboard, the iPhone LCD can display now！

iPhone 7 Boot without Display! Get solutions here!

 Recently, there's a strange thing happening on the iphone 7, it can be boot but withou display, the iPhone LCD screen just always black.  What's going on?  By the way, the iPhone 7 had been dropped before.

1. Disassemble the iPhone 7 by JM-P01 Electronics Toolkit,  then measure it with DC power supply, at the beginning, the current is about 350mA, and then the current drops and the iPhone reboots.  Usually, this problem was caused by iPhone Nand flash systme is damaged or it wasn't tested when loading with other peripherals.  Now, our initial judgment is that the Nand flash is empty welded or IOS problems.

2. Connect computer to flash, when it's ready to enter the normal mode, error 4013 is reported, then the phone into recovery mode. It doesn't seem like a system problem, so we remove the iPhone NAND Flash. There is no problem to test the NAND to the CPU resistance, and the iPhone NAND is read normally on the test fixture. As shown in picture 1, the NAND is welded back.

3. According to the result of above test, we can get to know there is no problem with the NAND. It seems something wrong with the baseband. CPU self check will also be some errors reported. From the picture 2, the baseband chip is removed

4. After removing the iPhone 7 baseband, no solder drop points were found. As shown in picture 3, using QUICK 861DW reworking station to weld the baseband back.

5. Reboot it again, the current is normal and the iPhone screen can be display now.  The iPhone 7  has returned to normal work.

SOLVED: iPhone 6 Plus half screen is black and the other half is bright

A customer has sent us an iPhone 6 Plus to repair, which problem is the half iPhone touch screen is dark and the other half is bright, sometimes even no display.

 

Because the customer only sent us the iPhone motherboard, after we received it, we checked it immediately. We found the motherboard repaired, and the iPhone backlight has been replaced. By the way, there is a capacitor that is not installed.

Now we directly remove the yellow insulation tape, cleaning up the repaired place, and then supply power on it to test, the left backlight is dark.

After using the QUICK861DW rework station to weld the capacitor that didn't install before, turn it on and test it, now the backlight is back to normal, it can display normally. According to check the WUXINJI circuit diagram, we know that the backlight is a step-up capacitor, if none of this; it can't boost the voltage, so the backlight is not bright.

After fixing the backlight, we also need to repair the screen sometimes display but sometimes doesn't display issue. Sometimes it can display when you press the socket with your hand, so we thought it was a problem with the socket. However, after careful examination, we found that the socket has been replaced, and the pin also is fine, now we have to check its circuit.

After testing, we found that there is no display power supply -5.7V. As we know, -5.7V is directly output by the iPhone screen display IC, testing the line, it is normal. So we decided to replace the display IC directly. After the replacement, turn on the iPhone, now the iPhone screen works normally!

Help! iPhone 6 Plus has no display after screen replacement

The iPhone 6 Plus LCD screen has replaced the new, however,  when we press the iPhone power button,  the iPhone screen has no display for a long time. It can receive the calls, just no display.  Let's get help here!

Check the iPhone appearance, there is no damaege.  Replace the new LCD screen,  the problem is the same: no diaplsy and no backlight.

The measured value is completely normal, there is no current burnt traces on the iPhone backlight chip and display power supply IC, so we can start to work on its display part.  Taking off the display IC under good protection, and work on solder pad with low temperature solder, do not rush to replace the new IC, the bottom resistance should be measured before that. As shown in picture 1.

The result shows that the D3 pin I2C bus CPU has no resistance to the clock signal of the display power, and the C3 display has no resistance to the power IC signal. According to these two results, we can make sure that the lock screw is wrongly installed to cause the motherboard layer being broken. Open the 6P bottom screws column diagram,we find that C3 go through left and right sides of the screw column, D3 only go through the left, After removing the 2 screw columns, we find both of them get traces of damage (you can remove the screw columns with solder paste, hot air gun with 300 degrees and gently push then down by QUICK 861DW Hot Air Rework Station), we find there is serious disconnection on the left. As shown in picture 2.

 

First, scraping a waste main board without broken wire and observe the wire construction. Select a smaller phone fix scraper tool, gentlely scrape and try not to damage the bottom wire since there are several layers in the iPhone 6 plus motherboard. you need to pay attention if there is black layer shown up for sraping the first layer, then you can add a bit of soldering paste on it, it will be clear to see the specific location of the wire under a microscope.

We choose a similar sharp knife to throw off the location of the broken wire and find the thread. The left screw can find a resistance thread. We choose a sharp iron with professional jumpers to solder every wire carefully and try not to repair it next time.

We can solder the jumper under the microscope, as shown in picture 3, the screw column on both sides of the line have in common, the left one can not find the thread so we can use the right column to make jumpers, then we measure IC bottom pin resistance again. The resistance is normal, now solidifying with green UV oil and install display power supply to test.

Now the iPhone 6 Plus LCD screen can be lit,  you can use the iPhone normally!