Chosen Solution
After my battery has been very weak for a while, my iphone 6s screen went black one day so I replaced the battery, but with no success. I went on to install a display replacement too, but still nothing. I also tried this thing I read about - unplugging the battery connector, pressing the lock/on and off button for 20 sec. and reconnecting the battery after as well as pressing the lock/on and off button again so it starts up . Nothing worked, screen is still black. The phone does get recognised by itunes however, telling me that it’s in recovery mode and I need to restore it. Also the option for “check for update” is greyed out/I can’t click it. The phone doesn’t get recognised by any data recovery software (I tried Stellar and Disk Drill), but as mentioned before, it does get recognised by itunes. Can restoring the phone fix the black screen at all or is it more likely a hardware issue?
It’s very important to always disconnect the battery before disconnecting/reconnecting the screen assembly. The issue is that the LCD connector has pins that have high voltages (i.e. the backlight is ~20V) and ground in very close proximity. When you fumble around trying to line up the connector plug to the receptacle, you can short out the voltage rail and cause damage to the components in the backlight circuit. If you’re lucky, then only a backlight filter is damaged but other times, the entire circuit could be affected. Either way, this type of repair requires micro-soldering and isn’t really a DIY repair. To test for this, plug your device into a charger or an iTunes enabled computer. Then shine a bright flashlight on the screen. If you can see a dim image, then the backlight circuit has been damaged. If you can’t see an image at all, then it may be the LCD circuit that is damaged. If iTunes doesn’t recognized the device than the problem is more than just a screen or backlight issue.
