Looking to repair a water damaged iPhone 4.

Hi there,

Long story short, I purchased a water damaged iPhone 4 from a friend for $25. He told me he had dropped it in his pool.

At any rate, I followed the normal procedure and removed the logic board, cleaned and soaked it with 95% alcohol, dried it, and put it back in the phone. No cigar.

I tried replacing the battery with a spare one I had lying around, once again to no avail. Close to giving up, I decided to try putting the logic board from the water damaged phone into my working iPhone 4 and lo and behold it booted up fine. This suggested to me that it was in fact not the logic board that was now faulty in the phone, but something else.

Thinking it was perhaps the display assembly, I removed the screen from my working phone and put it on the non-working phone with the new battery. Unfortunately, this proved ineffective as well and I'm rapidly running out of ideas.

To review, I know that the cause of the issue cannot be:

a)The logic board, as it worked in my other phone

b)The battery, as I installed a brand new one and it still wouldn't work

What else could I replace to make the phone functional again?

Thank you very much.