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!

Step by step to fix iPhone 6 screen blurry fault

An iPhone 6 show a variety of blur screens after booting, the backlight slowly darkens until the black screen. When we received it and check it, it's not dropped and water damaged. We judge the fault is in the iPhone screen circuit and the touch circuit (sometimes a zebra stripe appears after booting).

According to the common problems, directly replace the U2402 deputy touch IC and U1501 screen power supply IC, the fault still exists. We have to repair it step by step, now we open the WUXINJI circuit diagram, as shown in picture 1.

Use Fluke 15B+ Digital Multimeter to measure the J2019 screen connector socket power supply, reset, open and bus, all data is normal. Then we try to remove the U2402, but the problem still the same, the repairs falling into slow rhythm. Remove the U1501 screen power supply IC, and measure the diode data of power supply, reset, I2CO bus, all is normal, directly replace it, the problem still the same. The repairs again turn into the slow pace. Is the iPhone 6 CPU dead? Measure the CPU power supply, it is normal. Measure the power supply and diode data of EPPROM IC PP1V8 and I2CO bus, all is normal. What can we do now?

Continue to repair, focus on the reasons for the slow black screen. Check to see if the PP1V8, +-5.7V, I2C2 and MIPI power supply is working properly when they fade away. Quickly measure the signal that over the J2019 when turn on iPhone, we found that the voltage of -5.7V will continue to drop during the black screen until about 0.7V, other power supply signal is normal.

-5.7 is controlled by U1501, U1501 has been replaced by two, so we can eliminate its problem, now the focus has just been on the working conditions of the U1501 display power supply IC.

After close the screen, U1501 -5.7V slowly pulled down, +5.7V is not pulled down, after remove the all -5.7V filter capacitor, the problem still the same. Check U1501 peripheral circuits, the measured resistance of CHESTNUT internal charge pump circuit (step-up 6V) that was made up of C4 and E4 pin is normal, when close the screen and supply power on it, this voltage will jump, the problem is finally found. Remove the C1554, we found that the both side solder pads were all dropped after they were heated with MFC IREWORK Heating Platform, this position is difficult to weld the jump wire or mend the solder pads.

After thinking twice, we directly remove the UF31 screw column and U1501; soldering the jump wire from C4 and E4 pin, move the step-up capacitor near the flash chip.

Summary:

May be the user was dropped the iPhone during the use and then caused the C1554 solder pad and layer line is in contact with the bad state. The resistance is normal under no boot state, but when connect the load due to the boost part of the current is very large, excessive load leads to -5.7v output instability.  The picture of the repaired iPhone 6 is as follows Picture.

Solved: iPhone 7 won't boot and almost dead after dropping

Recently, we received one dropped iPhone 7 and one iPhone with iCloud lock from our customer, the customer describes the iPhone 7 was dropped, which without iCloud, but it doesn't boot. The customer wants us to fix it, and then change it to the iPhone which with iCloud lock. But now, we need to fix the dropped iPhone first.

After checking, the iPhone is hurting a lot by a serious drop. The screws on motherboard have been dumped, as shown in picture 6-3-1.

Connect it to UD 1505TA DC power supply first, it shows large current leakage. After measuring, we found the iPhone NAND flash 3V power supply was short circuit. After observation, we found the iPhone motherboard slot position is bent; the short circuit may also be in this position. After remove the two capacitors, which on the side of the NAND flash, detecting it again with DC power supply, now it can be turn on normally.

Turn on iPhone and test functions on iPhone, we found there is no WIFI; sometimes it will be stuck when into the settings. After measuring with Fluke 15B+ Digital Multimeter, the side of wife clock signal r0807 has 1.8V, the other side which is through to wifi module 17 pin has no voltage. Replace the resistance, and weld the jump wire by QUICK 861DWrework station, the fault is still exist. Decisively remove Wi-Fi module, and then the solder pad drops points, it is common in the iPhone that dropped, weld the jump wire first, as shown in picture 6-3-3.

 The WIFI module also drop points, we can check it under the 7-45X Trinocular stereo microscope. We want to test functions by turn on iPhone without installing Wi-Fi module, but when apply power on it, it's leaking again. Now, we need to use the rosin methods to fix it.  After remove the heating capacitor, power on iPhone and test it, the setting function is normal now. Next we need to install WiFi module, after finish it, test the function, the Wi-Fi is back to normal. However, sometimes it restarts automatically.

Considering there is a slight distortion in the middle of the iPhone motherboard, the audio can cause a reboot, so we remove the audio first, also drops points. After soldering jump wire, turn on iPhone and test it, all functions is normal now.

Now we need to replace external configuration. Use JM-P01 Essential Electronics Toolkit to disassemble the iPhone that with iCloud lock, please be careful not to break the line of the iPhone. Then replace the fingerprint that on the iPhone screen, because the under of fingerprint have glue, so please be careful not to damage the IC.

Finally, install the repaired motherboard, assemble the iPhone, turn it on and test it, now all is normal. The iPhone 7 has been repaired!

Troubleshoot: iPhone 6 Home button return function failure

We received an iPhone 6 to repair, the prblem of this iPhone is the home botton doesn't implement the return function effect, which means the iPhone home button not working.  We need to fix it!

After checking, we've ruled out external issues, we excluded the peripheral accessories issues and decided the problem is on the iPhone motherboard.

Use multimeter to measure whether the iPhone motherboard fingerprint socket J2118#3 pin has resistance, the data is normal. When measure the voltage, we found the BUTTON_TO_AP_MENU_KEY_L_CONN only has 0.6V, it is obviously been pulled down, the normal voltage is around 1.3V. You can check those pins on phone circuit diagram.

R0313 starts with 392K, now we change it to 10K resistance, and then measure it again, we found the voltage reached 1.4V, almost normal. So we assemble the iPhone and test it, we found it's still no return function after we install the fingerprint button. However, when we use tweezers to press the J2118#3 pin ground, it can return. We suspect it is a fingerprint key problem.

After measuring, we found there is a 20K current limiting resistance on the BUTTON_TO_AP_MENU_KEY_L_CONN of fingerprint key. Decisively remove that resistor, and then use the phone soldering station to directly short connect them. 

After finish the above steps, use phone screwdrivers to install the iPhone, power on it,  enter the IOS system,  and test the home button return function, not it works perfectly.