Fifth generation of iPhone. Repair of this device is straightforward, and requires screwdrivers, prying tools, and patience. GSM/CDMA / 16, 32, or 64 GB / Black or White.

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How to troubleshoot logic board after water damage and corrosion?

I want to isolate the component that is preventing an iPhone 4S from completing it's GO/NO-GO checklist. It appears to enter a boot loop when plugged in. It beeps (or buzzes if the ringer switch is toggled) regularly but the screen stays black. It shows up in iTunes but doesn't seem to stay powered on long enough to stay connected. Photos are accessible briefly along with all device info.

If I take out all the internals and connect the dock connector, logic board, and battery, will the phone show up in iTunes? In other words, I want to know if I can get the phone to boot through it's GO/NO-GO checklist with restricted functionality by disconnecting all components and then adding them back one by one (e.g. if the logic board boots with nothing else connected, then I'll add on the screen or try with a known working screen, then the home button, then speakers and microphone... not really sure what the best order might be).

The phone took a salt water dive and sat for a year so there are significant signs of corrosion inside. After mild scrubbing with a sonic toothbrush and vinegar, rinsing with distilled water, a 2 minute bath in 99% isopropyl alcohol and time to dry, it powered on and entered an apparent boot loop (woo!).

I may have some corroded circuits. Most of the board is in pretty good shape, but near the battery connector there is some corrosion that appears to have eaten away at this circuit:

For comparison I checked on a working iPhone 4S, and the gold circles are much cleaner:


I successfully experimented and discovered it's possible to get a logic board to boot to a more stable state by removing components.

My setup was:

  1. logic board
  2. connected battery
  3. dock connector
  4. USB cable connected to computer

I connected the battery and then connected the USB connector to the dock connector.

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To my surprise the board booted nicely. All information was visible in iTunes and I could get photos off the phone via Aperture (iPhoto probably would have worked, too). The only problem was the board would not stay connected for more than two or so minutes at a time. So I downloaded the photos in batches of 100 - 200 at a time, each time disconnecting by USB, reseating the battery connector, then replugging USB connector to reboot the board.

As dhsrusso suspected below, there was some corrosion at the connector pieces at the top of the board (notably the camera and the screen connector). I think the board would require microsoldering to fix and the extent of the corrosion doesn't really make it worthwhile. I could try cleaning the board again, but the extent of the corrosion and the fact that it won't even stay booted on its own means there are probably too many problems to fix on this board.

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the gold circles are test points--not required for function. keep the circuit writer pen away from your logic board always.

You are correct in your analysis---yes you can boot a board out of the housing.

yes this phone has tons of corrosion--salt water + time = tons of corrosion always.

Yes the board would require not just microsoldering, but extensive component replacement to function again--the gold circles are not important, but all the tiny completely corroded SMD components---like the one shown in your picture for example can be required.

Yes this board is unlikely to be restored to full function even with hours and hours spent microsoldering.

Water damage restoration depends on removing the corrosion and oxidation relatively quickly after the event. or being lucky.

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Thanks so much, Jessa! I learn so much from your posts. I scoured the web to find out about those gold circles and come up with very little. I appreciate your input!


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Take apart your iPhone 4s and clean all of the connectors and the logic board with a Q-Tip and use rubbing alcohol (isopropyl 90% only). This worked with my iPhone this summer when it got wet. It might sound weird to use rubbing alcohol on your iPhone, but it will remove any corrosion and it evaporates so quickly that it won't hurt it. Just make sure you gently squese out the Q-Tip before you rub it on the connectors or the logic board. Make sure before you put it back together everything is dry and all of the connectors look clean from dust. If you see black spots on a connector that might mean that that part is fried, so if any connector looks like that you will need to replace that part. You can buy all of your parts here on iFix It. Just know that Apple Care will be voided if you take it apart. One thing I would suggest, don't submerge the Logic Board in the rubbing alcohol or rub it on the screen. Hope this helps, please hit the like up arrow for me. I would recommend getting the iFix It version of each screw driver. iPhone Water Damage Repair. iPhone 4S Tear Down.

Make sure that you have all of the parts, so you can take it apart.


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I think that the gold circles are supposed to be their (Look at the picture.)

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Also look for any black dots on the connectors and tell me what they are. For example, look at the silver bits that are located in the box in the following picture and see if there are any black dots on them?

Metal Spudger Image


Metal Spudger


P2 Pentalobe Screwdriver iPhone Image
iPhone Image


Repairing iPhone Liquid Damage

Difficulty: Difficult1 - 2 ore

iPhone 4S Image


iPhone 4S Teardown

Difficulty: Moderate

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Thanks for the reply. I've actually already cleaned the logic board (though I could do it again -- I'm worried about causing damage). I'm wondering more about how to troubleshoot the logic board to isolate which parts might be having trouble. Do you have any idea what the gold circles in the pictures are for? Could I fill them in with a Circuit Writer pen?


I know I'm res-ing an old post, but I'm currently trying to recover an iPhone 6 using the same methodology. I was hoping that I'd be able to do the same and just plug in the necessary components just to perform the data recovery.

Do you know how long it took for your iPhone to actually show up in iTunes? Did you have it plugged in for a long time?


Hi Dan,

No, it took probably only 30 seconds for iTunes to recognize the stripped down logic board alone. Under a minute for sure and on an iPhone 6 I'd expect it to be even faster.

The real key to water damage is you have to give the logic board a good cleaning to get rid of any conductive residue that might be interfering with components. There are no guarantees and some components might already be damaged from over voltage. High percentage isopropyl alcohol bath (i.e. 91%) works well, and I used a sonic toothbrush to clean the board. Then be sure the board is completely dry before powering up (e.g. give it at least 24 hours or more in a warm dry environment - I used desiccant beads in an airtight container on a warm window sill).

Good luck and keep us posted!



Thanks for the input, Ariel! I gave almost all of the components a bath in 91% isopropyl and even ended up replacing the battery and lightning connector, but to no avail. I guess my logic board/flash memory was completely hosed!

Really good write-up, by the way. I think if my wife had gotten it out of the wash earlier, this might have actually worked!

Thanks, again and cheers!


Dan, I'm bummed to hear it didn't work out. I feel your pain! Frustrating to be sure. Sounds like you gave it a great shot though. Hopefully you learned something along the way so it wasn't a total loss (trying to look for a silver lining!). I also recently gave up on another water damaged phone - worked great for 6 months after alcohol bath, etc only to shut down randomly every couple minutes. Put it up on eBay for parts and see what you get for it. You might be surprised. Cheers!


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I am facing same problem with my I phone 6 it was water damage and almost 6 month after I trying to clean it after cleaning when I put it to charger it's flashing with apple logo .... So then what to do with my phone

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