Water damaged iPhone 4S issues

Iphone went through the laundry, it already had a broken LCD. i bagged it in rice for a few days, while waiting for new LCD to arrive. I took the phone apart to replace the LCD and a quick visual inspection showed no signs of damage or corrosion. i replaced the LCD and put it back together with a new battery. It turned on, the LCD was a little jumpy at first then it settled down. Everything seemed to work ok except the colors were a little off and it would not display the ringer volume bar when adjusting the volume. the volume would adjust it just didn't show it. I took it all back apart again and got out the loupe to check the board and contacts more closely. found a little corrosion on one contact and cleaned it with a small paint brush and 91 Iso and then cleaned the whole board according to guides here, including immersion of the board in iso. Let it dry thoroughly and reassembled. Now all i get is a white/gray screen. It worked nearly perfectly yesterday, now nothing. Replacing coils etc. are way beyond my ability. I will try swapping parts with another iphone over the next couple days to try to narrow down the problem. If anyone could suggest a different solution it would be appreciated.