Chosen Solution
So my friend broke his iPhone x and had it at a repair store. Front screen is broken and they told him, that the problem is the motherboard. At that time, the screen showed the batteri when powered, and “in need of charge” when no power was connected. The phone has been in his drawer ever since and now it doesn’t show anything when putting it to power (but it gets a little hot). Does anyone know Where i start? I got some microsoldering equipment, but never used it. How do i diagnose the problem?
You would have to assume the repair shop gave the correct diagnosis. They would have ruled out parts. If they didn’t you will need to replace the screen, battery and dock assembly and test the phone with only these connected. You can prompt to boot with your lightning cable. This is how we know if it is a logic board issue. If it doesn’t boot after preforming the above actions you will need to see how much current it is drawing, for this you will need to connect it to a DCPS with a squid or an iPower. Depending on the result you would either be looking at the charging circuit components or another line. Remember these are double layer boards so you will need to split them as most of the components that stop the board from booting are on the bottom side of the top layer.
Have you tried to replace the screen yet(guide here)? If not, I would try that first.
