Chosen Solution
I have an old iPhone 6 that I hadn’t used in about 6 months, and I decided I wanted to use it again. Even though it worked the last time I used it, it won’t power on at all. I plug it in and nothing comes up on the screen. I plugged it into a computer with iTunes and iTunes doesn’t detect anything at all. The charger cable certainly works because I’ve tested several with the phone and it works on other phones. I opened the iPhone up and took the motherboard out and I don’t see any damage. There’s no water or physical damage to the phone. When I plug it in and feel the motherboard, after about 30 minutes it feels a little bit warm, certainly not hot or anything, just barely warm. The home button on the phone does not work.
It could be a dead battery after all this time. It also could be that it died when you tried charging it. After all, we’ve had a lot of people bring their dead iPhones after they left them to charge and woke up to a dead device. In this case, there can be a number of causes that make a board unresponsive. Such as shorted backlight circuit, shorted power rail, dead Tristar, etc. (I love those, we get them a lot and if they have not been tempered with by a wannabe board tech before us, we usually get them all back including data - dead iPhones are my favorite). So in summary it seems to be a board level failure and if the iPhone is not brain dead (failing CPU) for some odd reason, it should be repairable by someone who performs board level repair.
Given the long time without being powered and I assume being an iPhone 6, probably a worn out battery, it’s not much of a surprise it doesn’t turn on. Batteries left drained may go bad even if in decent condition..just replace it, probably that’s all it needs to be done.
There must be problem in your battery, or in your charger, Check both of them by replacing them. Or Better, Go to Apple Care and they will help you.
