iPhone 6 Water Damage

[eDigitCom]

iPhone 6
Water damaged - No further History
Have not removed the shield to inspect the board so far
Measured Short on PP_VCC_MAIN

Reading taking on a DC Power Supply shows High current and low voltage

Going by the reading I get (see attached image)

R = 1.6/1.16 = 1.4 ohms


So looking at this measurement without taking any further reading there is 1.4 ohms in the circuit hence a short to earth. The calibration of the meter etc may be causing to give the reading of 1.4 ohms


Is this enough to tell you have direct short to ground




Thanks

[Jessa_the_Professa]

iPhone 6
Water damaged - No further History
Have not removed the shield to inspect the board so far
Measured Short on PP_VCC_MAIN

Reading taking on a DC Power Supply shows High current and low voltage

Going by the reading I get (see attached image)

R = 1.6/1.16 = 1.4 ohms


So looking at this measurement without taking any further reading there is 1.4 ohms in the circuit hence a short to earth. The calibration of the meter etc may be causing to give the reading of 1.4 ohms


Is this enough to tell you have direct short to ground




Thanks

Yes. But you don't want to put electricity into a board that you think has a vccmain short until you've cleaned it with the shields off. Because of this your multimeter is your best tool to detect a common short on vccmain.

Method 1: Diode mode readings; red probe on ground, black on line (this is iphone repair standard convention). Compare reading to known good. If low = full short or partial short. (Quantitative but requires known good)
Method 2: Continuity mode--one probe on ground, other on line side of any vccmain cap. Beep to ground on line side of cap = full short to ground. (Easy, doesn't require known good.)

vccmain is connected to battery power rail, so a full short on vccmain will be the same as shorting your dcps alligator clamps together--immediate and strong current consumption--->Hence, let's get that board cleaned up and try to clear the short first before putting dc voltage into a short.

[eDigitCom]

Thanks Jessa.

Thanks for the advice about putting electricity into the board but do you need to do this test once to see if it is drawing to mush current or not??

After the above I have taken the resistance measurement from VCC_MAIN to ground and it is giving the Beep (zero ohms) . I also used the diode mode has you explained and showed no reading.


I done this test with other iPhones and a good reading would be approx 0.4 volts. I have seen you using the diode method on your videos and the reading you would expect to get if no short to ground.

I agree before I go any further I need to remove the shields and inspect the board further and clean it. This I was thinking myself

For me to do this I will have to get an Ultrasonic Cleaner which I do not have at present but I am going to get one after Christmas??

To use it I would need step by step instructions??

I think to myself you have water in the Ultrasonic Cleaner/ So I say is this not like putting the phone into water again???


The phone did power up for me at the start and the reading taken from the DC multimeter were correct at that stage?? I powered it up using the DC supply has the battery was dead.

I did notice a small amount of corrosion around J2118. I cleaned this with some Isopropanol 9.9% pure and left it for about 3 hours to dry out. After this the phone would not power up. Then doing the measurements above the short was on the board??

I cannot see how Isopropanol would have caused the short to appear unless it cleaned some area that caused the short to occur??


Would Ultrasonic Cleaner remove the silicone waterproofing ??

Thanks This forum is well worth the money

[Sly]

Hi eDigitcom
The Ultrasonic Cleaner wont remove the silicone waterproofing, but before doing all that. Are you repairing the phone for educational purposes, data recovery, or to have a long term working phone of a customer?

I'm asking partially because of your questions about the Ultrasonic cleaner. If you're attempting to fix the phone just to learn how to fix a water damage board, that's great, and you don't necessarily need to have an ultrasonic cleaner to get it operational, at least for a little while. You can clean the board by hand with an appropriate brush (AKA toothbrush hehe) and the isopropanol 99.9% (it;s made of none conductive materials) you used for J2118.

The idea of the ultrasonic cleaner is that the vibrating (none conductive) microscopic bubbles will reach in places you can't reach with a brush, and therefore makes for a better cleaning. This is especially true if conductive or corrosive material has reach under a BGA chip since you can't reach there with brush.

Once the required shields are removed(you might want to practice this if you have not done it often and are working on a customer's board), you've cleaned the board from visual mineral deposits,corrosion, and measured key power lines for shorts or low resistance you can start contemplating connecting it to a source of power.

Before introducing any kind of electricity in the circuit , your first objective should to free it from any mineral deposits on the board that could short it out or give you bad readings.

And go from there.

[Jessa_the_Professa]

Vccmain short after water damage is such a common fault that it is probably worth it just to check with a multimeter first before putting current into the device. As we can see here--device initially did not have a vccmain short, now it does. Why? Because it is still sprinkled with salt and then electricity applied before cleaning it---electricity goes through Salt and can electrically damage caps and chips on the line so that you now have a short where there was none before.

lesson: never put electricity through water damaged boards before cleaning.

ultrasonic cleaning is like washing dishes. It loosens corrosion, then you scrub by hand with alcohol and dry.. Water by itself isn't bad--it's the combination of water, dissolved stuff, and electricity that is bad. This is why putting devices in rice is a bad idea--it allows the entire battery voltage to expend into the wet device, then makes people feel they've "done something" so they then put the device on a charger and apply more electricity to a salt covered board. That makes easily cleaned focal damage turn into widespread damage that isn't feasible to repair.

[eDigitCom]

Great advice and lesson learned Thanks Jessa.

It looks by I doing this caused the short

I will remove the shields next and inspect the board

after this I wait on my Ultrasonic Cleaner to clean the board

I think you said it is pointless on one of your videos buying a cheap one has it would not do the cleaning correctly so it think it would better for me to be looking at the one you have in your tools list. Thought expensive it would pay for itself in the long run. I hope??

So the bottom line is to check the board for damage and shorts first. NOT connect it to a power source

Great explanation about water on its own Now it makes complete sense to me. Never thought of this before. I knew electricity and water not go well together. No fuse on an iPhone to blow like in a in a person home

. This the reason if a person gets water damage I advice them to get the battery removed has quickly has they can, WHY I not think of this, - not taking my own advice?? and putting it back to the stage when the battery was connected.

I told by many customers they put there phones into rice and this is one for the first question I ask,

This phone was put into rise for 2 weeks?? I suppose you cannot blame them has all over the internet they tell you to put it into rice.

This dries the phone but causes more corrosion I hear ??

Is it the best think to just let the phone dry out by itself and get the battery disconnect has quickly has possible

If you get a water damage phone is the correct way to go about it is to clean the board even if all measurements are correct and the board by inspection looks good?? In other words do you have to clean all water damaged boards no matter what in an utrasonic cleaner

Been here only 2 days and have learned quite a lot


Thank You

[Mark_S]

You should remove the shields and clean any board with liquid damage in a sweeping frequency ultrasonic cleaner. Then check for short on VCC main and if there is no short, connect dc power and prompt to boot.


Regarding your OP, a short with very high current consumption and very low voltage will always be some sort of significant physical bridge between the line (in this case VCC main) and ground. In some cases it can be a solder bridge you have created yourself but in this case it is likely to be corrosion under an ic.

[eDigitCom]

Thanks Mark_S

[eDigitCom]

Jessa can I just follow on from this please

So say VCC_Main is shorted to ground. Then the shields are removed, cleaned the board and inspection - everything looks OK but still there is a short on VCC_Main

So then comes the stage where to use the freeze method where you first spray the board and then inject current into the board and check for the component that melts first


Is this not dangerous to do has you are sending a current of 1 amp to 2 amps into a board that has a direct short to ground. Will this possible do more damage??

[Jessa_the_Professa]

Freeze spray is a tool you use when you have no idea where the short is--i.e. Everything looks perfect. I did two videos last night--both phones had a short circuit. I used freeze spray on the first because it was not water damaged and there were no visible signs of damage. Heat detection was my only tool. On the second, I did not use freeze spray because it did have physical damage on visual exam.

on a water damaged board, you will have visual signs. Where did the water go? Start there