iPhone screen only comes up white

[AshD]

i have just installed a new screen on this damaged iPhone I had bought from somebody. I have no idea if the iphone had this problem before the new screen installation, but after I installed the new screen, the only thing that i can see is a white screen. Everything functions the way it should on the phone, it syncs okay, it vibrates, makes normal noises, but I have no idea what is wrong with it. The headphone jack does not indicate any water damage, so I'm out of ideas. I have tried holding the home and power button and restoring it. Also, the screen assembly is okay and have tested it on another iphone and have found out that it works flawlessly, so i'm guessing it's a hardware malfunction. Any suggestions on how to fix this is much appreciated, thanks.