iPhone 7 Won’t Turn On With Large Current
Malfunction Phenomenon
iPhone 7 won’t turn on, very large current once we connected with DC power machine.
Trouble Shooting
Large current means somewhere is shorted, because once the motherboard was connected with DC power machine, current jumps to very high value, we can conclude that the short issue happed before the phone was turned on.
There are several sets of power already stand by there once we connected with battery or DC power machine. For iPhone 7, there are 3 sets of power, PP_BATT_VCC PP_VDD_MAIN, and PP_VDD_BOOST. Any components on these 3 sets of rails shorted will make the large current issue.
For this issue, we checked PP_BATT_VCC line first by measuring the diode value on pin1 of battery connector J2201, the value was 438, which was normal, which means the PP_BATT_VCC line is normal. Then we continued to check PP_VDD_MAIN line by measuring the diode value on test point TP0408, the value was 0, this line was shorted. We also checked the PP_VDD_BOOST line, it was also normal.
We checked the relevant components on PP_VDD_MAIN rail under the microscope. After we checked carefully, we found one capacitor C2610 was black.
We removed C2610 and connected it with DC power to test again, the short has gone, we assemble with the screen, the phone was turned on, problem resolved.
