The Most Common iphone Motherbaord Repairs by i-Station
iPhone Backlight repair
Do you have an iPhone 6 with no back light or stuck on medium brightness?
A blown back light on an iPhone 6 is typically caused by a screen gone wrong or a sudden drop on the phone which can damage some of the components on the backlight circuit.
To confirm that the backlight is no longer working, disconnect the battery, reconnect it, then plug in a USB lightning cable. Immediately shine a bright light on the center the screen and you should be able to see a faint apple logo. That will confirm that there is a problem with the backlight system.