Guides I've Contributed To
I suspect it'll be because the little black rubber shroud that sits over the proximity sensor has fallen off when you did the cable transfer. I had a client phone come in the other day and I noticed it was missing ( from a previous repair ) and asked if they'd been having issues, and they have, with poor face-presence recognition and similar. To date I've not yet found a supplier of replacement units.
Same has happened here, nicely smashed front glass, replaced the whole frontal assembly just to be "quick and easy", alas to no avail, touch screen doesn't respond, tried with old/original unit, still doesn't work either. I fix a few iPhones/iPods a week and 3G (and 3GS) units are usually the simplest of them all, but this time it looks like it might well be an onboard controller fault :(
The problem is quite common. It's the fault of one of the main NEC/TOKIN capacitors located directly beneath the CPU (on the other side of the board). The reason why it works on battery but not AC is because there's no significant ripple in the power when running from battery, but on AC there is a fair amount which causes unreliable behaviour. Replacing the capacitor is not a trivial task even for those who deal with surface mount replacements. Typically we just break off the old TOKIN capacitor and install a set of tantalum caps in its place.
Try this solution... Press and hold the home button, then the up-volume button, then the sleep/power button (so all three buttons are now pressed and held) --- it takes a while, but the white screen will go away and then after another 10 seconds or so (still holding btw!) the apple logo will come up, release the buttons and then wait, it'll boot normally again in a minute or two. EDIT: Just tried it on my own 3GS here which decided to go into the WSoD - alas, doesn't seem to be working this time, not sure though if it's the buttons or not at fault. Update: If the home-up-sleep combo doesn't work ( as I encountered recently ), it might be worth letting the unit run flat for a few days and then plug it in and try the home-up-sleep combo again. I was surprised, I thought I was going to have to bin this 3GS but amazingly it came back to life for me. Not sure what the difference is, but perhaps during the total power-down phase the iPhone manages to go through some different stages in the firmware, as opposed to r...
Warm it up a bit with a heatgun, makes the bonding adhesive a bit softer and you can then lift it up safely with a spudger.
Shouldn't there be a disconnect-battery step, before attempting to remove the screen cable hold-down panel?
Agreed. It's a serious omission.
Many times it won't matter, but occasionally something will touch in the wrong place and *plink* the phone is broken.
It sits between the logic board top-edge and the two ribbon leads from the screen. Its purpose is to stop the PCB cutting in to the FPC leads over time due to vibrations. If you require I can send a photo.
I recommend that steps 20 and 21 are swapped. It's much easier to remove the wifi antenna flex from the board using the blue spudger if the board/PCB is still secured with the 4.8mm screw.
Removing the screw first makes the PCB move up too much when you're trying to detach the wifi flex and can lead to mishaps.
Couple of ways to get rounded-out-head screws;
1) use a tiny drop of super glue on the top place your screwdriver on the drop/screw, then sprinkle a bit of bicarb-soda on to the wet super glue, it'll harden very rapidly and form a fillet; wait a minute and you should be able to then unscrew the screw.
Be VERY CAREFUL when doing this, because you don't want to have superglue wicking between the screw and the circuit board.
Perhaps practice on some other things first.
I've removed several like this before; frequently I find the culprits for rounded out slots are ham-fisted people trying to do their own repairs in the past.
Please, Please, PLEASE avoid using probing elements to try remove batteries. I have had dozens handed in to me with punctures and two that actually started smoking due to people trying to prise the battery out. DO NOT DO IT.
The best way I have found to remove the battery is this process;
1) Try remove it with the pull tab directly, some will come out, some will not. Do NOT use excessive pull force else it'll deform the battery and reduce the capacity.
2) If the pull test didn't work, then get a hot air gun on medium and warm up the area around the battery for about 30 seconds, focusing on the perimeter of the battery. If you see ANY popcorn'ing then you're too hot, you don't want to cook the battery.
2.1) Wait about 30 seconds for the heat to now wick underneath the battery to soften the adhesive.
2.2) Now try pull the battery up, the extra heat should have softened the glue that you can remove the battery without excessive force and without sticking objects under the battery.
Do NOT use a spudger or similar type of prising tool to try lift up the battery. Instead, just warm up the whole area with a hot air gun or hair drier to soften the glue.
The reason why I say don't use an implement to try lift the battery is because far too many times I've seen punctured & bent batteries come in to this workshop that have to be thrown out for safety reasons. It only takes a grain of sand, or a burr on the spudger and you're risking a potential cell rupture and potential fire.
Just use a bit of heat ( not a lot! ) to soften up the glue and it'll come away with the plastic pull tab.