Logic board heats up as soon as it's put in
Hi there. I bought an iPhone 3G 8g and at first it wouldn't turn on at all. I have since worked out that the battery was completely dead when I got it. Put it into another iphone3g 8g and charged it then put it back into original phone but before I even got to putting the screen back in the logic board was so hot I had to take it back out with tools. Just sitting the logic board into place no screws no conectors attached it gets very hot closest to connector 5 and 6. Does this mean all is lost?
Replace the battery with a new one. It should not have anything to do with what iPhone you charged it. Since it charges in one, but not the other phone, you may have a different problem all together. Since you are not sure, what works and what does not, start at a known good point. A new battery is not very expensive, but will provide you with that point. Do you know anything about the history of the phone? I would treat it like a liquid damaged phone first. Clean it according to this guide Repairing iPhone Liquid Damage While you clean, do a visual inspection. Use a magnifying lens to look at the SMD (little electronic components on the board) and see if anything looks like it is out of place. As for the place where your phone heats up, not exactly sure since I can't see your phone, but it does not sound like the power management IC. That one is located on the right lower half of your board. Battery charger and USB IC is on the left upper half of the board. iPhone 3G Teardown step 19 will show you the component layout. Check your dock connector as well, look for bend, corroded pins and again for missing or burnt looking components. Once you have it cleaned, and installed a new battery, keep it disconnected from the rest of the phone for a couple of hours (overnight). Do not rush things by being overzealous. Anyhow, give it a try and let us know how it is going. Good Luck. BTW also try to use an Apple AC wall adapter to charge. Some of the "cheaper" aftermarket ones can really fry your battery and your board.
This just happened to me today on a 3gs. I suspect it wasn't the battery, but the logic board.
I've had the logic board in the phone once before, testing to see if it worked. when it did not work right away, I took it out. Today, I thought maybe I rushed the assembly and maybe missed a connection, so I tried again. As I was replacing the screws, I started noticing the heat increasing very rapidly. I rushed to remove the screws and the logic board.
The logic board was a purchase, so I don't know the history accept "phone was dropped and does not turn on", but I do know the phone works, without overheating, with a completely different logic board. Still not sure if I did something wrong in the assembly, but it heated up so quickly, I was afraid to try again.