Chosen Solution
I had no power to my iPhone 5s, and was unsure if it was the lightning port or the battery. during disassembly, the battery took on some damage, and the lightning port failed a test. so I ordered replacement parts for both. After completing the repair process, I reassembled the device and went to test it, and the same thing as before. No response. I tried plugging into the wall, my laptop, tried holding buttons down to restart, but nothing worked. I doubled and even triple checked the cables to make sure they were connected, and still no response from the phone. What is, or could be, the cause of this?
You could drive without your seatbelt for years and never need it either. Just because it works 99.9% of the time doesn’t mean that it isn’t the wrong thing to do. If you repair a large volume of devices, you should apply best practices. That way, when you do occasionally forget to unplug the battery, the odds are in your favour. Replacement batteries are notorious for poor quality (as are small parts). I would try another, known-good battery before going the micro-soldering route or try these parts in another phone. If a fully charged, good battery does not work, then it is probably not a U2 problem per se. U2 communicates with your charging device to determine if something is connected that can charge your battery. Tigris controls the MOSFET. The MOSFET is a power device and doesn’t fail that easily.
So sorry to hear about your problem Ethan. It seems to me like the phone just has a motherboard issue, and can most likely only be repaired by micro soldering which requires a lot of time and skills. If there is any possibility that the phone had any contact with water at any point, that could also be an issue. You can tell a phone is water damage if the small white sticker is red, or if you just notice any white dusty particles anywhere on the mother board. A motherboard can also cause a shortage when the phone is being taken apart but the battery is still plugged in. I dont know if at any point you unplug any of the connections while the battery was still plugged in, but if you think, you did, then that is definitely the issue. I hope this was of some help, if you have any other questions please ask. You are also more then welcome to give me some more details so i can try to further investigate a solution for you.
TriStar switch (U2) or the charging mosfet Q2 is the issue
