I got this iphone with water damage. I opened it and sprayed the MB with dry contact cleaner. After reassembling it turned on and the only thing that was not working was the gyroscope, so I disassembled again and tried some more dry contact cleaning, now it does not turn on. The screen remains on the empty battery, it was 100% charged. Any clue?
So technically it does "turn on" as you can see the low battery indication on the screen. Maybe you forgot to reattach the battery connector the 2nd time?
No I tried many times, I tested the Tristar and it’s good, it reads 3,80 volts circa , the battery is also good.