3G and GSM connectivity suddenly lost
So, I have an iPhone 4S which a little over a year ago ended up in the water. As described in this Intermittent signal or "No service" after water damage I first replaced the dock connector which was the first component to become corroded, but soon I found out also of the more vital components was also affected by corrosion. This caused the phone to drop drop 3G connection (and eventually GSM) and going into "No Service" state.
I took it apart and cleaned with isopropyl which gave me about 2 more months bore the issue returned. At that point I took it to a professional technician who ended up sending it to china for repair (they're apparently better at the really tiny components) and the phone has worked perfectly for about a year since I picked it up.
Now, from out of the blue it has started to drop its connection. I noticed it when suddenly 3G intensive apps stopped loading data, and subsequently found out I could also not make or receive calls. The thing is though, that it still displays a normal signal bar and 3G symbol, and the connection seems to be quite intermittent, coming and going every couple of minutes.
I feel this phone has served me well, and it might be time to retire it. But I would love it if I could keep using it until I can get my hands on a new iPhone 5S, which might mean 1-3 months I think (haven't seen an official release date for Sweden yet).
So, I just though I'll ask for some tips on where to start the trouble shooting. I'm reasonably skilled at taking it apart and cleaning it having done a complete teardown at least two times, but I'll prefer a minimum effort. Should I just do a complete isopropyl scrubbing or focus on a specific part such as the 3G antenna? What might be the likely causes for the issue returning - corrosion build up, antenna issues, battery wear and tear? Grateful for any help and tips!
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