Chosen Solution
Hello, TL;DR After changing battery and front speaker, the iPhone only boots normally when either the front camera assembly (old or new) or the home button (old or new) or both are disconnected. Long Version I’ll start chronologically and tell you step by step what I have done, so that you can maybe spot the problem. I recently had problems hearing my partners on calls. I suspected too much dust on the speaker, so I decided to thoroughly clean it. Since I had to open my phone anyways and the battery had only 80% of its original capacity, I also decided to change the battery as well. Before I started I updated my device to iOS 13.5. Opening the device I had a hard time to to get the spudger initially between display assembly and lower case. I had to pull really hard on the suction cap I put on the lower part of the screen, despite I had warmed the glue with a heat gun set to 100ºC (212ºF). The I disconnected to battery connector, then the display, home button and front camera assembly connectors. I then removed the top speaker from the front camera assembly so I could clean all the dust which had been accumulated during the years (it was a lot). I cleaned it by carefully blowing the wire frame out with compressed air and wiping it with a q-tip and isopropanol. Then I put the speaker back in place, changed the battery and connected everything back to the logicboard (power cable last). When I tried to start the device it got stuck in a boot loop. It showed the apple logo, then the screen turned to black and the iphone rebooted. First thing I tried was putting the iPhone in DFU mode and resetting the firmware. No success, nothing changed.Then I read that a faulty front-camera or proximity sensor could be the case (maybe I had damaged it with the compressed air). So I changed the front camera assembly to a new one. No success, nothing changed.Then I tried changing the front speaker to a new one. No success, nothing changed.Then I tried removing the connector of the front camera assembly from the logic board. Now the iPhone started, but the home button was not working anymore.Then I kept the display assembly disconnected and removed the home button connector from the logic board as well. Now the iPhone started, but the home button was not working anymore (since it wasn’t plugged in anymore).Then I left the home button unplugged and reconnected the front camera assembly. The iPhone booted normally. Front camera, front speaker, ambient light sensor and proximity sensor were working (Have tested all of them). And the home button of course was still not working since it wasn’t plugged in.When I connected the home button back to the logic board the iPhone was stuck again in boot loop.Then I disconnected the home button again, this time I left the home button connector on the logic board plugged in and just disconnected the home button on the backside of the display. The iPhone is booting again normally, but now home button (since it was not connected anymore).Edit 2020-05-26: I’ve now also tried a new home button. As soon as any home button is connected the boot loop appears. So the iPhone only boots normally when either the front camera assembly or the home button or both are disconnected. I don’t suspect the front camera assembly to be broken, since I’ve tried two of them, both resulted in the same error and when it was connected while the home button was disconnected all sensors where working properly. I also don’t suspect the connectors on the logic board or flex cables to be broken or having a short, since the iPhone is booting when all of them (but the home button connector on the backside of the screen) are connected. Where do you think could be the error? What am I missing out? What could I try next?
It sounds like the only thing that works is if you leave the home button disconnected from the screen. My guess is you have a defective home button. You can buy a replacement one for around 10 dollars from ifixit. The replacement home button will work normally but touch Id won’t work because the factory home button is paired to the motherboard. I home that helps.
