Poor wifi on iPhone 6 Plus? Here can fix it!

 A customer sent a iPhone 6 Plus motherboard to us, the problem is that there is a poor wifi on iPhone 6 Plus,  the WIFI signal is weak,  it doesn't work properly. Please don't worry, here can fix it!

First of all, we install the motherboard on the iPhone by phone opening tools, and then we can test the Wi-Fi signal. After checking, we found its wifi signal is weaker than the normal iPhone.

Next, we remove the motherboard to check, the WiFi connector circuit is not damaged, in many cases, most of repairmen would directly replace the iPhone WiFi IC if the WiFi itself gets damaged.

But now we can put it under the advanced VGA 7-45X Trinocular Stereo Microscope to do careful observation, the motherboard is very beautiful, there is no water damage trace, the first consideration of fault is pressed parts.

Indeed, we can see the IC be pressed under the microscope , of course, do not first think that WiFi itself under pressure, sometimes the next filter will also suffer pressure. The following picture 10-4-1 is pressed IC fl_cell_rf with false welding, also with minor cracks.

Take care to remove the IC and the small inductance. Losing inductance will also cause weak WiFi signal, of course, it is also possible to solder jumper wire to solve this kind of situation. And then reinstalling IC fl_cell_rf .

Finally,  install the iPhone again, get into IOS to test WiFi signal,. Now the WIFI signal is back to normal! 

Troubleshoot: iPhone 6 Plus common touch issues

 As we know, the most easily damaged part of the iPhone 6 Plus is the touch. The iPhone 6 Plus touch  failure includes iPhone touch screen uncontrol,  screen hopping randomly,  zebra flicker on the top of the screen and so on.  Now, we troubleshoot it step by step.

First of all, replace a new screen to test, if the issues still exist, then we can start to detect the iPhone motherboard.

Test the ground resistance of the touch pin, which can intuitively let us find out where the problem is. At the same time, we can see that the 18 pin is the synchronous signal of CPU through the black touch M1 pin. If all these resistances are normal, voltage test should be started. By voltage test, we can more accurately judge which chip is damaged.

The voltage test must be buckled to the screen for voltage output, three power supply for black touch: +-5.7V shows power supply, and 1.8V shows it is given by power IC . As shown in picture 11-12-2.

Two power supply of white touch : 5.1V display power supply, 1.8V power supply IC. As shown in picture 11-12-3. It is possible to judge which IC is damaged according to the results measured.

The water damaged device shows that the power is easy to burn out so that 5.1V and white touch +-5.7V cannot be given. Broken device fault mostly shows on black touch, false welding is the most possible problem. During the soldering process, some technicians do not remove and redo but directly heat to the chip, customers can use them normally, but they will come back to repair after a while. It is better to take the chips off and replace the new ones.

The point of the black touch M1 pin is at the top of the plate layer, and it is easy to break the wire to cause the iPhone 6 Plus CPU signal to not be delivered, so we need to use the jumper wire to solve this problem. There is a point below the R2410, and the M1 pin is a circuit line, gently scraped with a blade under a magnifying glass, then get a little solder on the blade, blowing a small solder ball out with ESD hot air gun, it must be small, then welding the solder ball at that point scraped out with slow speed air gun, using a copper wire (can take off from solder wick) to fix on the scrape point and M1 pin, add the green oil and put under curing UV light. The process looks more complex, but the effect is very good, and it is basically no rework necessary.

In addition, take care not to damage the small components around the points, here are 2490, FL2486, C2439 three components,which are used for identifying the original screen, after you change the iPhone touch IC and install the original screen, if the screen is still not responsive but assembly screen can work, that is the problem. 

After installing the black touch IC, check whether the resistance of C1577 is normal, because it goes into IC, and it is surrounded by grounding pins. If the current is directly loaded onto 500mA on Fluke 15B+ Digital Multimeter, most of them are caused from here.

In the end, just be careful and be patient during the repair process!

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!