iPhone 4 No Display But Lights Up (Backlight working)

I recently acquired an iPhone 4 32GB. When i first received it it was totally unresponsive.

After replacing the battery and scrubbing the logic board with (90% Proof) alcohol and replacing the screen it turned to life. However i could only see a black screen, it did light up but with no apple logo appearing. It is highly visible so i know it is not a backlight issue.

First thing i tried was to do a hard reset - Power and Home for 10-15 seconds, with the result being a reboot but the issue still persisted. Then i removed the logic board and repeated the alcohol clean to make sure no corrosion remained.

I have tried 3 different screens which all work on other phones. Two of the screens show a black screen and the other a white screen (it had been slightly damaged).

I have restored in DFU mode and downgraded from 5.1.1 to 5.0.1. I have also tried different batteries as well as putting the logic board in a completely different phone to no anvil!

The only thing i haven't tried is soaking the board in alcohol. I may try this unless anyone can offer some other tips/advice as to any solutions I could try? I have already search the deepest depths of google but no method seems to work!

Any help in the slightest would be appreciated!

Many Thanks in Advance