Justin Berman

If you purchase a clean, non Apple ID locked logic board then yes it would fix your problem. If you can get ahold of the woman who sold you the device, all she has to do is login to iCloud.com with her Apple ID and password, click on find my iPhone, find said device, and click remove from account. Once that is done the Apple ID should be lifted. Expect to pay almost as much as you paid for the phone for a new logic board.

In most situations the home button link cable is at fault. It's the cable that runs up the back of the EMI shield, that connects the home button to the logic board. Try re-seating or looking for tears along this cable. If you have another shield with a link cable attached, try installing that.

A possible fix is going into Settings < Accessibility < Display Accommodations < Turn Auto Brightness Off Then go back to Settings < Display & Brightness < Turn Brightness all the way down Go back to Settings < Accessibility < Display Accommodations < Turn Auto Brightness On It helps to do this in a dark room. If this fix doesn't work, it could be a loose pin on an individual cable, or a short in the board during the repair.

The screw that secures the home button for the iPhone 7 is very finicky. You almost have to find the right amount of pressure (not too loose, not too tight) in order to get Touch ID/Home button functionality back to normal. Seeing as though this was a used phone that was opened up and compromised prior to you receiving it, you are taking shots in the dark, not knowing if the Touch ID/Home button was fully functional when you purchased it.

The straight cable is related to cell signal strength. The angled cable is related to GPS signal strength. ^ Taken from the link @john provided

If you log back into iCloud.com and go back to find my iPhone, you are going to look for "devices" and click on it. Find your iPhone, click on it, then click "remove from account"

Do you have the ability to try a different glass/lcd, so that you can isolate this to a part issue or a board issue? Also, make sure there is nothing out of place on the device that could add a pressure point causing the discoloration.

When you say new touch IC chip, did you desolder the chip and resolder a new one, or that you think this is touch IC disease related? Or did you mean a new touch ID button was put on this device during the glass repair? In my opinion this is either the home button link cable not being seated to the board properly, and/or that the front facing camera cable was damaged during the repair and needs to be replaced. You should also look for a small metal grounding plate that is located above the touch ID home button connector, right below home button link cable on the original screen, that needs to be brought over to the new screen for optimal touch ID functionality.

Try unplugging the battery without your power cord plugged in and holding the power button down for 10-15 seconds. Then plug the battery down to the board, plug the charger into your computer, and try turning it on.

If you are hearing fans speed up right away it is definitely that LCD temperature sensor cable. If you have the tools, I would pull up a repair guide and see if you can't adjust that cable. A cheap and easy possible solution would be to replace it.