Follow this guide to repair iPhone 6S touch screen not working problems. This guide offers you a very detailed logic board repair solution of the problem which the iPhone 6S touch screen is not working after dropping into water. If you want to learn more about iPhone touch screen logic board repairing guide, follow the more comprehensive version that covered most of the iPhone model here.
Failure Phenomenon:
iPhone 6S touch screen not working anymore after cell phone dropped into water, and the display touch base has been replaced already.
Maintenance Procedure:
There is a big difference between touch circuit of iPhone 6 and iPhone 6S, and the touch chip of iPhone 6S is integrated into the screen display digitizer, moreover, the display and touch of iPhone 6s share the same connecting seat. The display of the iPhone 6S is shown in pic 1-1.
iPhone 6S's touch display connection seat Pic 1-1
AS the display and touch ICs are integrated into screen display digitizer, the motherboard only provides power supply, clock, reset, INT signal interruption and SPI bus communication to the touch circuit. When the iPhone 6S touch screen not working, as long as you can turn on the display, you won’t need to measure PN5V7_LCM_MESON_AVDDN, PP5V7_MESON_AVDDH, and PP5V7_LCM_AVDDH, because touch and display also share these functions. The circuit of required voltage touch and display is shown in pic 1-2.
Required Voltage Circuit Diagram of Touch and Display Pic 1-2
It is generally required to measure the ground impedance value of the J4200, as well as the voltage of PP5V1_TOUCH_VDDH and PP1V8 when screen display assembled. The location of the measuring points is shown in yellow in pic 1-3.
Touch Display Seat Testing Position Diagram Pic 1-3
After testing, we find that the ground impedance value and voltage are normal. Then we changed a new screen display and assemble it for testing, the touchscreen is still not working.Since the iPhone 6S has a 3D Touch feature, the touch screen not working may also cause by the 3D Touch functioned abnormally. The 3D Touch is connected to the fingerprint connecting seat, after measuring the ground impedance value of fingerprint connecting seat, it is found that AP_TO_TOUCH_RESET_L signal is a little bit lower than normal at only 80, and normal value should be about 400. Then let's check the bitmap and find that the reset signal of AP_TO_TOUCH_RESET_L is connected to the display touch connection, as shown in the yellow point in pic 1-4. Moreover, the ground impedance value of the AP_TO_TOUCH_RESET_CONN_L on J4200 is normal.
AP_TO_TOUCH_RESET_L Connection Diagram Pic 1-4
The measurement shows the AP_TO_TOUCH_RESET_CONN_L on the touch base and the AP_TO_TOUCH_RESET_CONN_L on the fingerprint base are disconnected. Remove the black glue on the edge of the fingerprint and find that FL4134 and C4134 and several elements on the side are all corroded. After replacing the corrosion components, the touchscreen and the 3D Touch function are back to normal during testing. The position of the corroded elements in the bitmap is shown in pic 1-5.
The Position of The Corrosion Elements in The Bitmap Pic 1-5
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