Chosen Solution
I bought a broken iPhone XS Max which has a smashed back and a screen that has a working display but wouldn’t respond to touch. Also, the screen had what looked like a small“dead pixel” from the impact, visible when powered on. It appears that the impact happened to the back since the display is not cracked. I replaced the screen/digitizer with a brand new one from Ebay but it still doesn’t respond. I was under the impression that all of the logic for touch was in the screen itself. Apparently not. I’m assuming the issue is with the logic board. Aside from the unlikely possibility that the new display is also defective. Can an expert advise me on where I should be looking for damage that would cause touch to not respond? Is this something I might be able to fix with a soldering iron?
You are on the right track, but remember the logic board has to relay the touch info to the processor and the screen is plugged into the logic board. If the board took a big impact and any traces were broken during the impact, then you may be out of luck. I don’t micro solder so I don’t know if there are any fuses etc that can go out or need to be replaced, but your issue is more than likely a board-level issue. Id find someone reputable to send it to.
