iPhone 8 Plus - no backlight - no boot

[artem]

Hello Everybody

I'm glad to be a part of your community ))

This is my very first post so apologize if anything

HISTORY :

A customer brought an iPhone 8 Plus saying it was in contact with snow. And no power anymore

The phone was opened previously as the screen was replaced.

Motherboard looks just fine except some oxidation

WHAT WAS DONE

After I opened it there was still lot of liquid inside

So I removed all shields and put it in ultrasonic bath.

After cleaning everything the phone seems to power on but not boot till the end.

So I can see the apple logo but after it powers off

MEASUREMENTS

Didn't really know where to start, so I measured both screen connectors in diode mode

On J5700 all values seems correct except for pin 5 where I get 2.6 instead 1.8

Also on J5800 all values seems correct except for pin 22 where I get 2.6 instead of 1.8

I also replaced R5756, C5756 and R5785, just in case )) with no results

I'm getting 4.3V on C5695

And 4.3V on C5650

So the backlight driver seems to work

Do you have any ideas where else should I dig ?

Thank you for your support

Best regards

[Jessa_the_Professa]

You have a brain dead phone. Taking the shields off is very aggressive for iPhone 8–I would only do that if I had no other choice to solve a known problem. The heat from shield removal is now a really big variable—did it kill CPU, loosen a connection, overheat EEPROM? Or was this phone brain dead from the actual water damage? We don’t know.

The problem is where the water went.
Where did the water actually go?

feel free to post crisp pictures of the board

[artem]

Hey Jessa thanks for your reply ))

There was some oxidation in that area and that cap - C5804 was also replaced

I used to remove and put back shields in the past with no issues )) Don't think its due to that.

But how to make sure that there was no liquid damage underneath without removing shields ?

Regards

[artem]

oh here is overall view on the mb

[Jessa_the_Professa]

Looks like the overwhelming majority of this board never saw water—which is often the case. It is likely brain dead due to software corruption from trying to start too many times with wet “parts” ie battery, charge port—or heat/bend from shield removal (I would never remove the soldered on shield near charge port—too much risk to the EEPROM, and CPU shield only if I was sure that water was under there and causing problems. It is too big of a variable. Similarly, I would not remove waterproofing on components near charge port etc unless I had to. Try not to introduce variables.

Either way the next step is restore to correct software corruption. Use a known good housing not the wet one.

[artem]

Thanks for your reply and Happy New Year ))

Ok I don't know how but after I put the device in dfu mode several times I've got back the backlight and was able to restore the iphone.

Was waiting for customer to provide the passcode so I can recover his data !!

I thought it was fixed but then the backlight disappeared again

It seems to work now as I have haptic feedback when click home button but with no backlight.

Thank you for your support

Best regards

[artem]

hmmm now it works again

kinda don't want to give it back to customer and him be back soon saying it wasn't fully fixed ))

[Jessa_the_Professa]

This phone never had a natural backlight problem—it never had water at backlight. The original problem was software corruption and it needed restore/update all along to solve. Apple logo/loop is an information problem. Remember—backlight-no image is the normal appearance of a phone in DFU. This is why DC power current consumption is our main tool to help us tell the difference between image problems and auto-boot to DFU.

If backlight is now intermittent that is not from water, it’s from the aggressive troubleshooting. The connector may be stretched, or the heat used for shield removal at the coil array near the charge port could have lifted the internal backlight coil which is located within that chip so that it makes poor connection.

recover the data and don’t guarantee function of the phone. Next time be more cautious and don’t take off soldered on shields on iPhone 8 unless there are signs of water.

[artem]

hmmm

the issue was no image or no backlight first of all and corrupted ios later i think

when phone gets to dfu mode its not black screen but an image with computer and stuff, before it had total black screen and we had no idea on what was going on ))

now the phone works perfectly fine just need to get back the backlight

if i don't remove shields i have no idea if the water got inside or not it also not prefect to ultrasound the mb with shields on !

here some pics

As you can see water was everywhere and in the area responsible for backlight too

With all due respect, saying thats my fault doesn't really guide me to troubleshoot the issue )))

Also we can assume thats not cpu/eeprom issue as it works but without backlight )

Thanks for your support

[Jessa_the_Professa]

I'll give you some advice, you can take it or leave it. These are the strategies that I use personally.

1.) iPhone 7 and 8 series--never take off the bottom soldered on shield. (Why? Because there is nothing under there that can get bothered by water, and heat near the coil array is really bad)

2.) Ultrasonic cleaning is usually overkill for most iPhone 8. Usually water can be spot cleaned with alcohol and toothbrush. Only if the case is severe with corrosion on the BOARD itself would I ultrasonic clean an iPhone 8. You have to take off the CPU shield to ultrasonic clean, and that will destroy the thermal paste and compromise the board long term.

3.) DFU and Recovery mode are not the same. DFU shows backlight no image after Apple logo. Recovery is connect to iTunes logo. Both are form of "brain dead"

4.) "Braindead" phones: Any phone that shows low or cycling current consumption on DC power supply when booting. This includes auto-booting to DFU, Apple logo boot loop, auto-boot to recovery mode, or low mA. This category broadly means "information problem" and is a form of not booting. Phones in this category do not have image or backlight problems--they do not boot because they are missing required signals/information for booting.


Now let's review this case and how we'd approach it from the top.
You have a wet phone. Is the board actually water damaged? Answer--No. There is very minor liquid on the board. Treat with toothbrush and alcohol and move to DC power test.
Should you remove sticker shields and have a look--Yes. Very minor liquid.
Should you remove soldered on shields? No--there is not enough water damage on the board to suggest that water is under there.
Should you ultrasonic clean this board?---No. Same reason.
Water inside the housing we don't care about--only on the board, and only damage/green/oxidation/corrosion.

Next step: DC power and known good parts. Does it boot?
You said "I can see the Apple logo but it powers off" = brain dead, but image and backlight are fine.

DC power would have shown a normal boot sequence that stops midway and begins again.
This means it is brain dead. The phone is missing required information to continue the bootloader. Braindead can have many causes, but the easiest to rule out is software corruption.

Next step--restore (or if data is wanted, update)
In this case, the board would have updated just fine because the braindead problem was software corruption. (We know that because you said it passed update and booted).

Next step: evaluate the "parts" can the charge port, camera, be saved from the original housing? Look for water damage/corrosion on the parts and test parts individually after the data is backed up, replace battery. Test each part. Does the phone still boot and operate? (Tip: iPhone 8 wet charge port and battery can make a phone braindead)

That would be the cleanest approach to this case. Toothbrush and an update with known good parts = solved.

If you saw the Apple logo way back at the beginning of this case then you never had a backlight or image problem. Image problems can't produce Apple logo. Backlight problems have a dark screen.

When you are learning, it can be hard to tell apart "no backlight, or no image" from "not booting" power or brain problems.
Learning to use the DC power supply as your primary tool will teach you whether or not the phone is booting.

Read back through everything you did with the knowledge "this phone never had anything wrong with it other than software corruption from wet parts" Think about how you might change your approach for the next phone.

[Romychopra111]

i'm so amazed with the information, thankyou Jessa for this information, More respect!!

[artem]

ouahh ))) thanks for those advices really appreciate will take more care next time

so even if i messed up for this one.... it works just fine now except for the backlight )))) 😂😅😅😅😅

What I did so far :

- replaced the backlight driver U5600

- replaced the lcd connector ))) 🤣😂🤣😂

- was getting 1.4 (diode mode) on pin 23 of J5700 - replaced C5710 + FL5710 - now getting OL as it should (didn't notice the first time)

and still nothing ))) phone boots i can see icons and everything but still just no backlight

Also replaced R5730 and R5733

thank you for your support

[artem]

ok replaced U5660 and U5650 and C5604 🤣😂😅😅😅😅

seems to work now

still testing but no random backlight issues anymore