iPhone 6 Backlight working but no image

Hi,

My friend came to me with his iphone 6, and the screen wasn't turning on. After repeated replacements with a few different screens, I did an iTunes 'Update' reset in Recovery Mode. After this, i noticed that the backlight was coming on, but there was no image on screen. I have since hard reset, and nothing still comes on. I have used 3 different screens including the original, so please help.

Thanks

Leo

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