Chosen Solution
Hi guys, I have an iPhone 7 here. Dead, won’t turn on. Upon testing, I found the pp_vdd_main line is shorted. Using freeze spray, I noticed that coil L3704 on the chestnut line is the first to melt. After removed the the coil L3704, vdd_main was no more shorted, every cap on vdd_main was back to normal. However, after a new coil L3704 was installed, vdd_main became shorted again. Once again I removed the coil, I found one pin on motherboard is shorted to ground. See attached photo for the shorted pin. Does anyone know how clear the short on the coil?
Well a coil is, in essence, a short between two points; it’s just a coiled up wire. Take a look at the circuit below:
If PP_VDD_MAIN is not shorted to ground when the coil is removed and it is when a coil is installed, the thing to take away from that is that either there is internal trace damage or there is internal damage in Chestnut (U3703) which is pulling pin B2 to ground. Remove the coil and probe the pads to see if one side of the coil is shorted. If it is, then the problem will be on that side (most likely U3703). If that is the case, remove Chestnut and see if the short is still there (inner trace issue?) or gone (bad Chestnut).
