Chosen Solution
I did follow the guide to replace my iPhone 7 back case. Everything went smooth, I’m 100% sure I didn’t mess with screws (everything was tagged and I also made photos after every step), but before final reassembly I decided to check if my phone works only to find out it doesn’t boot. Apple logo appears for 15 seconds, then phone switches off and on. 15 seconds later everything repeats, and phone never finish the boot. Things I tried one at a time (and they didn’t help): Disconnected front cameraDisconnected whole display assembly (it didn’t appear in iTunes).Disconnected back cameraDisconnected back assembly (lightening port and audio speaker). This way it looped faster (in 7 seconds instead of 15)Disconnected power button assemblyConnected new front camera assembly I also tried to put iPhone in DFU mode in restore firmware. It succeeded both times, firmware check also succeeded, but iPhone still doesn’t boot. The only thing different is that it loops in 7 seconds instead of 15 like before. I’m really stuck and don’t understand what I can check at this point. It doesn’t look like Audio IC or modem issue other users are having here, also it shouldn’t be front camera assembly, as I tried to boot without it (and boot with a new assembly) and it doesn’t work too. UPDATE: Could someone confirm that iPhone 7 with latest iOS 12 should boot WITHOUT front facing cam ribbon and Touch ID? I know that was an issue on iOS 11 and I’m trying to understand if I have a logic board or display ribbon cables issue.
What makes you think it doesn’t seem an audio IC issue ? The iPhone housing replacement was done as the old one was damaged/warped ? If that’s the case it’s when such issue happens most often, as a consequence of pressure put on the logic board causing flexing. Bootlooping on iPhone 7 unfortunately points in that direction..
I ended up applying for professional service, they told me that memory got corrupted. Not sure how it happened, but they fixed it
