Today we had a customer in with an iPhone 6S that just randomly died. When plugged into our ammeter we could see that there was no current draw from the charger.
We opened the phone up and connected it to our DC power supply. When connected there was an instant 5 amp draw telling me that there was a full short on the VCC main power line.
We removed the logic board and inspected the vcc main line for any obvious signs of damage or burning. There were none. We know the 6s commonly shorts on the bottom end of the 6s near tigris so we covered this area in freeze spray and injected voltage directly into this line to see what components get hot. This proves what component is causing the issue. We saw that C3795 was getting hot so removed this with our micro tweezers.
Once we removed this capacitor we checked for a short on this line, which was now cleared. We replaced the capacitor with another and plugged the phone back into the dc power supply. This time when plugged in there was no current being drawn until the power button was pressed and the phone began to boot. This is how it should work. We waited for the device to boot and tested basic functionality which was fine.
We were able to return this device to our customer within the same day and get them back up and running with their phone again in no time.