Just added a OEM Battery to my iPhone 3GS 16GB, I refurb iPhones as a hobby. This model has indeed been tiersome.
I Bought a £4 battery off ebay, which was yellow, (a fake to be honest)
I think!... Then when i was turning it on/off it would crackle and not hold the power long from the dock. (about 3minutes)
I bought a new OEM dock. (£8) and a OEM white Battery (£7) and now i have re assembled the iPhone, and plugged it into the (Mains) not by USB to PC but by Wall socket.
Left for around 40minutes. came back turned on. and it shows a white screen. Tried the Home and Power 10 second rule. but it does not turn off it just shows white. So im simply leaving on charge till i get a response. If it fixes with extra time charging then i shall post.
Ill try re attaching the screen, but not always sure its the problem. the connector 3 on the lcd replacement maybe loose as when fitting the screen it can pop up without you knowing and when secured down the screen it may be this.. but usually the screen wont show a picture without it secure.. so the white should not be showing.
I installed the latest firmware 5.1.1, all working showing display, new casing, attena, new docks, batterys, screen etc But was not picking up a signal and crackling . also did not hold power away from a usb power source.