When we touch the iPhone display screen, it has no response, the iPhone 6S touch screen doesn't response to touch. This touch failure occurs after water damage, we tried to fix it by replacing the iPhone screen, but not working. Is there something wrong with the motherboard?
Disassemble the iPhone 6S, remove the iPhone touch screen, disconnect the iPhone battery, and then take off the iPhone motherboard.
Use Fluke 15B+ digital multimeter to measure diode data for iPhone display touch connector J4200 some Pins, the diode data and voltage are normal.
As we know, the abnormal iPhone 6S 3D Touch function also will cause iPhone touch screen can't be used.
Sign in to the ZXW online account to check iPhone schematic diagram, we saw that the 3D Touch is connected to the iPhone fingerprint connector.
Use digital multimeter to measure the diode data for the iPhone fingerprint connector, it's found that the diode data for AP_TO_TOUCH_RESET_L reset signal is smaller than normal value, it's only about 80, while the normal value is about 400.
Check iPhone bitmap, we know AP_TO_TOUCH_RESET_L this reset signal is connect to display touch connector.
However, the diode data for the AP_TO_TOUCH_RESET_CONN_L on the J4200 measured is normal. Continue to measure, it's found the AP_TO_TOUCH_RESET_CONN_L of the iPhone display touch connector and AP_TO_TOUCH_RESET_CONN_L of the iPhone fingerprint connector are not connected.
Put iPhone motherboard under a Black Trinocular Microscope, and then use BGA graver to remove the black glue, we found the FL4134 and C4134 and several components next to it all are corroded. Clean up the corroded components, and then measure it again, now the data tested is normal.
Finally, install the iPhone 6S and test the iPhone touch screen, now it's working.
Disassemble the iPhone 6S, remove the iPhone touch screen, disconnect the iPhone battery, and then take off the iPhone motherboard.
Use Fluke 15B+ digital multimeter to measure diode data for iPhone display touch connector J4200 some Pins, the diode data and voltage are normal.
As we know, the abnormal iPhone 6S 3D Touch function also will cause iPhone touch screen can't be used.
Sign in to the ZXW online account to check iPhone schematic diagram, we saw that the 3D Touch is connected to the iPhone fingerprint connector.
Use digital multimeter to measure the diode data for the iPhone fingerprint connector, it's found that the diode data for AP_TO_TOUCH_RESET_L reset signal is smaller than normal value, it's only about 80, while the normal value is about 400.
Check iPhone bitmap, we know AP_TO_TOUCH_RESET_L this reset signal is connect to display touch connector.
However, the diode data for the AP_TO_TOUCH_RESET_CONN_L on the J4200 measured is normal. Continue to measure, it's found the AP_TO_TOUCH_RESET_CONN_L of the iPhone display touch connector and AP_TO_TOUCH_RESET_CONN_L of the iPhone fingerprint connector are not connected.
Put iPhone motherboard under a Black Trinocular Microscope, and then use BGA graver to remove the black glue, we found the FL4134 and C4134 and several components next to it all are corroded. Clean up the corroded components, and then measure it again, now the data tested is normal.
Finally, install the iPhone 6S and test the iPhone touch screen, now it's working.

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