Check this iPhone 6S Plus again, it doesn't display, keep black screen, now let's start with software solution, and then hardware solution, because the hardware solution is more complicated than software, it requires professional phone reapir skills and phone fix tools.
1. Force restart iPhone 6S Plus
Frist we can try to fix it by force restarting, because restart iPhone can fix many simple software errors.
In order to force restart iPhone 6S Plus, please press and hold the iPhone Home Button, while holding the Home button, press and hold the Sleep/Wake button, continue holding both buttons for about 10 seconds, until the Apple logo appears.
2. Update iOS
Try to fix iPhone no display issue by updating iOS, usually, there are two ways we can do, one is update it on iPhone, the other one is update it by iTunes, here we need to update iOS by iTunes, because the iPhone is black screen.
In order to update iOS by iTunes, connect iPhone 6S Plus to the computer, and then open the iTunes(latest version) on computer, click Summary, and then click Check for Update, click Download and Update if the iOS update is available.
After update iOS, check iPhone again, the iPhone 6S Plus screen still no display.
3. Restore iPhone 6S Plus
Restore iPhone can deepest solve iPhone software errors, and this is the last software solution we can do. We need to back up the iPhone before we restore it, because it will erase all data of the iPhone.
After the back up, use iTunes to restore iPhone, and then check iPhone again, unfortunately, the iPhone 6S Plus still no display. We need to use hardware solutions.
1. Replace the new iPhone display screen
First we need to disassemble the iPhone 6S Plus, take out the iPhone display assembly, and replace the new iPhone Display Screen.
2. Measure the iPhone motherboard
Take out the iPhone motherboard, measure it with DPS DC power supply, the iPhone current tested is normal, but the iPhone still no display, this failure mostly is caused by iPhone display screen abnormal power supply.
Measure the diode data of the display screen interface by digital multimeter, no short circuit or open circuit was found, next to measure the display power supply.
When disconnect the iPhone display screen, the capacitor C4002 on bootstrap circuit of power supply chip U4000 measured by multimeter is 2V voltage, which is lower than 6V voltage, it is abnormal. Check the working condition for U4000, all is normal, so we judged that the U400 internal is damaged.
3. Replace the U4000
Put iPhone motherboard under the Stereo Zoom Microscope, and then use QUICK 861DW hot air rework station to replace the U4000.
4. Install the iPhone 6S Plus
Finally, install the iPhone 6S Plus, turn on it, now the Apple Logo appears properly, the iPhone LCD screen displays normally.
Hope the repair method in this article is helpful to you. If you have a better way to fix black screen of iPhone problem, please leave a comment in the comments.