iPhone Won't Boot (No Apple) After Screen Replacement Solution
iPhone 4 won't boot at all after screen repair - no apple logo. Slight flash on the LCD when it attempts to boot.
This is a solution to a very specific problem. Here's how to tell if you do have this problem:
1. Your iPhone boots normally without the new screen connected, but when you attempt to turn it on with the new screen connected, it won't even show the Apple logo.
2. Your old screen works on your phone but the new one doesn't, making it seem like the new screen is faulty or not compatible.
3. Your iPhone is running iOS 5 or less.
For more information: http://www.kirtrainford.co.uk/?p=184