Broken back light iPhone 4

gears

Over the weekend I dropped my phone, not very far just off the sofa but it looks like the back light is broken.
If you look at the screen under bright light and tilt it you can make out the display and there is no cracks or breaks in the glass it's just very dim.
As I didn't notice the problem immediately, when it fell I just picked it up and put it in my pocket, I thought it might be some unrelated software issue so I have tried all restarts and reboots and nothing works and it's running the latest OS.
So it looks like I'll need to change the back light and I'd like to do it myself. I've googled his and found lots of guided, ifixit being particurlarly good but none specifically look at the back light alone.
Does anyone know of a guide to fix this or do I need to change the whole screen?
Thanks

Mr Deeds

Commiserations on the fall and subsequent damage.

The backlight on the Iphone usually stops working if there is water damage. The water usually fries a part called the Backlight Coil - you would have seen these in the Youtube videos you refer to -
However, I have seen cases where drops onto tiles don't crack the Digitizer or the Screen but will damage the connections internally - it might be worth trying to reseat the connectors inside the phone, but you would need a bit of know how to get this done. Easiest thing is to bring to a shop - they should be able to test it relatively quickly and give you a price on the repair - last thing you want is to replace the screen and find that it is the main board that needs replacing -
Hope this helps.