Diagnose white screen resulting from water damage?

My 2nd gen 32Gb ipod touch took a dip in a canal. This was months ago and has been fully dried out. I have taken it apart and cleaned both sides of the logic board with isopropanol. Basically everything works (before and after disassembly) except there is a streaky white backlit screen when I turn it on:

- Speaker and headphone jack works

- Receives email

- I can take screenshots

- Touchscreen works - even though I can't see it, I can unlock, change screens and launch apps (evidenced by screenshots)

I don't think its the LCD as I plugged in a different LCD that I ordered and it also came up with a white screen. I did this when I had it apart before cleaning with alcohol.

So does this mean the logic board is fried? If it is is it only the part driving the LCD since everything else seems function except the screen?

What is the diagnosis and what are my options? ie sell the thing for parts?

Thanks