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Repair information and guides for the fifth generation of iPhone. Model: A1387

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iPhone 4S motherboard overheating after water damage cleaning

I got iPhone 4S, it was water damaged, I took it apart and cleaned it with Isopropyl, took apart the motherboard and cleaned it, and all connectors.

I replace dock connector and battery.

Now when I turn on the phone, it works but the motherboard gets really really hot, until I HAVE to shut it down. Battery stays cool.

When I plug charger, it shows the little symbol of "charging" although the battery level keep going down and not up.

Must be some component on the motherboard, right?

Is it a hard fix?, does the phone even have a chance in this world?

Thanks so much for any help.

Answer this question I have this problem too

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4 Comments:

It appears that you are having issues with either the charging coil, charging IC or any component thereof. These components are wither BGA IC's and require a rework station, or they are minute in size and very difficult to solder for the average DIY'er

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You must be right oldturkey03, i asked a few techs, and some didn't wanna touch the phone, only one store was nice enough to give me a 170$ quote on replacing the charging coil. There is no chance that my Electronics Engineer brother can do it with a professional soldering tool?, only a rework station can manage that??

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If your brother has the tools, I am sure that he knows how to use those, he could replace the coil. I mean at this time, you do not really have anything to lose by letting him fix it for you.

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i had the same issue: i checked the heat source and recognized that the back camera went really hot during phone use. to check this i unplugged the connector of the back camera, then it did'nt went hot any more. After a week i plugged it in again and it was in normal temperature and still full funcionally. Good luck.

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1 Answer

There's clearly a shunt somewhere drawing current. I would first check your reassembly to make sure all the parts got back together correctly. As I recall there's a piece of insulating tape near the camera - make sure that's in place.

Another item to check is the connector to the display. Make sure it's clean and properly seated. The backlight power feed goes through that connector and it's one of the bigger power draws in the phone. Pull that connector and check with a magnifying glass for any possible shorts.

Don't scrub the surface of the board. There are some very small SMD parts on the board. You can scrub some of those right off the board if you're not careful!

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Oh, well I didn't know not to scrub the motherboard, so i scrubbed it twice. All th guides say to scrub it.. !@#$.

But i am pretty sure i didn't pull anything off the motherboard while scrubbing, because the phone works correctly. Just that it overheats.

I called a tech and they said i'd cost like 150-200 bucks and that there is a need to solder a new "charging component" and I saw online there is a site selling 2 things for problems like mine: Charging component and a charging fuse of some sort. but i can't find the site anywhere, only saw it once.

Can those things be soldered with a regular soldering machine?

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Well this is way after the fact. Sorry I just saw your comment. For the record, soldering on a cellphone board requires special equipment to do correctly. A low-power microscope (stereo is best), a solder rework station, a board pre-heater, etc. I did a bit of that on one iPhone 4S and it was very difficult to do. I don't recommend trying unless it's something trivial like reattaching a wire.

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