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Infinite bootloop after water-drop repair

Hi, so I have an iPhone which has been dropped into water. It was’t working at all, so I fixed it by cleaning motherboard with isopropyl and changing battery with new one (as the old was dead).

When the battery came, I just briefly connected all things together so I can see if it will boot up. It did. I was happy, so I just assembled it all (didn’t put display back into chasis yet) and tried to boot it up now. I was really surprised when I found out that the iPhone was in infinite bootloop (apple logo for 5 sec, black screen for 5 sec, repeat).

I read on the internet there are way many things that can be wrong at this point, but if it was working disassembled just connected together, why is it not working now? I checked all connectors, cleaned it all with air, checked for any weird things with lens, but couldn’t notice anything.

I will try to get you a photo, but for now, can I ask if this is familiar to you in any way and do you have any suggestions on what I can try next? I am really dissapointed it didn’t work.

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You will need to do a restore with iTunes or 3Utools.

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First,water damage is unreliable. Cleaning the board definitely can help,but if component damage happened,what’s done is done. You’d have to have the component replaced. Sometimes an ic chip can get water underneath it and corrode the solder balls. The metal plates that are soldered to the board that cover the cpu and chips could have water under them. If they got corrosion,you can’t really clean it very well unless you remove the shields,which requires a soldering skill.

I assume you took the whole logic board out to clean? If so,are you positive you put the screws back into the correct holes? Long screw damage is a thing.

Now if it’s not water damage causing the reboot,I’d say did you connect or disconnect the screen before disconnecting the battery first? Did you possibly knock any components off? If you mixed up your screws and put one in the little metal ring nut(like the ones directly attached to the board for the lcd plate screws),it could have been a long one into a smaller hole and dug into the board.

Did you try disconnecting the camera flex cable to see if it did the same thing?

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Hello, thank you for your reply. I know that water damage is a thing where things can turn badly over time, so I was counting on some issues. The only thing I didn’t understand is that it was working when I just connected cables to test it. After gettin everything in place, putting most of the screws and connecting everything I got a loop.

I am sure I didn’t knock off any component, I was proceeding with caution and slowly. About the screws - I didn’t get to the part of screwing up the plate holding lcd flex cables, and I checked the logic board, there is no visible damage.

I tried to disconnect and disassemble everything again and now I connected it like this: power button flex cable, lcd and digitizer flex cables and battery flex cable. So just basic things (without camera and other not neccessary things) to try to boot up again, but without success.

I have to dismantle the shield covering the cpu and check for the issues there as you said, I have some soldering skills so we will see how it turns out.

It’s very easy to knock components off even if proceeding with caution.

If you remove the shields,especially the cpu shield,you need to be very careful. If you overheat it you will make solder balls under the cpu pop out. It is under filled with glue,and the heat makes the glue expand at a different rate than the solder liquifies. If you make the solder liquid,it will solidify within a couple of seconds when you pull the heat away. The underfill will still be expanded and stop the solder from rebonding with the pad.

If you have a good hot air station(not hair dryer),you can use around 450c(if the temp is actually accurate),at max airflow. You have to hold the plate with tweezers and pull it off as fast as you can. If you hold heat too long,the phone’s toast.

The rest of the shields is the same thing. The best thing to do is hold the phone by the shield you’re removing,and let it drop when the shield is ready to come off. Hold it a couple inches or LESS from the table.

You really need a microscope to do repair though. It’s very easy to screw stuff up with microsoldering,especially without LOTS of practice,good tools,and a microscope.

As long as you’re not concerned about data,you can keep trying.

And it’s always possible you have a short. You’d need a microscope to look closely and clearly at it. You’d need a dc power supply(a supply that you can control voltage with and monitor current draw) to see if it pulls excessive current.

Thank you, I will try my best, I have all of these stuff, so I will try my best.

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