In this guide, we will explore how to diagnose and repair an iPhone XS with an unresponsive touch screen. An unresponsive touch screen can be a frustrating issue, but by following the steps below, you can potentially resolve the problem.
Initial Inspection
The first step in diagnosing touch screen issues is to examine the iPhone’s motherboard. Check for any deformities or signs of water damage, as these can often be the root cause of touchscreen problems.
Initial Testing
After ensuring the motherboard is in good condition, install it and connect the display and battery. Power on the phone and check if the touch screen is still unresponsive.
Pinpointing the Problem
If the touch screen is still not working, proceed to measure the touch connector. Pin 21 of the connector might be open-circuited, indicating a potential issue in the circuit connected to this pin.
Resistor Examination
Pin 21 connects to resistor R5842, which is a safety resistor. Test the resistor’s integrity using a multimeter. If the resistor is intact, the fault likely lies within the middle layer circuit.
Separating the Motherboard
To access the middle layer circuit, carefully separate the motherboard. Use a heating platform at 160°C, and once the adhesive softens, remove the logic board and signal board with tweezers.
Circuit Assessment
Since the other end of the resistor connects to the power IC through the middle layer, start by checking the circuit on the logic board. Ensure that the resistance value is within the normal range.
Then we separate the motherboard. Put the motherboard on the 160 °C Heating Platform to heat. After about one minute, remove the logic board and signal board with tweezers. It can be seen that the motherboard has been separated before.
Open the bitmap. The other end of the resistor is connected to the power IC through the middle layer. Therefore we need to measure the circuit on the logic board firstly. The value of resistance is normal.
Identifying the Fault
Measure the circuit between the signal board and the touch connector. An open-circuit condition indicates a problem. To resolve this, you’ll need to perform a jump wire repair.
Jump Wire Repair
Apply Paste Flux to the resistor and solder a copper wire to it using a soldering iron at 360°C. If the two ends are too far apart, secure the copper wire in place with Solder Mask. Use a UV Lamp to solidify the solder mask and then check for its stability.
Because the two ends are too far apart, we need to fix the copper wire in the first place. Apply some Solder Mask. Solidify with UV Lamp. Check if the solder mask is solidified with tweezers. Next, fix the remaining copper wire with Solder Mask.
Cut the copper wire. Solder one end of the copper wire to the signal board. Measure with the multimeter. The value of resistance is 0, which indicates that the circuit between the touch connector and signal board is connected. Solidify pads on the signal board with Solder Mask. Scrape to show the pads. Clean the bonding pads with PCB Cleaner.
Then we recombine the signal board with the logic board in a direct way. Put the signal board on the 160 °C Heating Platform to heat. Apply some Paste Flux to the bonding pad. Put the logic board in position. Press gently with tweezers during heating. After about a minute, remove the motherboard.
Reassembly and Testing
Carefully recombine the signal board with the logic board using a heating platform at 160°C. Once the motherboard has cooled, measure pin 21 of the connector. If the resistance value is back to normal, you can install the motherboard for a final test. If all went well, the touch screen should now be fully functional.
Conclusion
Repairing an iPhone XS with an unresponsive touch screen can be a complex process, but with the right tools and techniques, it’s possible to identify and fix the issue. If you’re interested in learning more about motherboard repair troubleshooting, you can check out REWA Academy’s comprehensive course package. Additionally, they offer live online repair courses for those seeking face-to-face interaction with experienced technicians. Feel free to explore a variety of repair topics and leave comments on subjects that interest you.
For more repair techniques, visit REWA Academy. It offers a comprehensive motherboard repair troubleshooting course package to enhance your repair skills.
