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iPad Rehab

Practical Troubleshooting for Sustainable Repair

February 1, 2015

 

So this thing isn't turning on...

 You're holding an iPhone in your hand and pressing on the power button to no effect, what is your next step?

Step one--Is this No Power? Or just No Display? 

At first glance, what seems like a no power problem--the phone shows nothing on the screen--could actually be just a display problem.  Many things can cause an iPhone/iPad to lose it's backlight--water damage, cheap screens with exposed solder joints at the backlight flex, shorting the backlight circuit accidentally by using metal tools while the phone is under power....  For more info, read Backlight 101.

Sometimes the phone can have the backlight on, but show no image.  Remember--the backlight circuit is separate from the image circuit.   No image is most commonly tool/fingernail damage near the display connector which have popped off a data filter from the board.

It is relatively easy to differentiate a display problem from a true no power problem.  With no display, the phone is technically on, you just can't see anything.  Connecting the phone to the computer will tell you if it's on or not.  If the phone is recognized by iTunes for example, it's on, but you have a display problem.   If the phone is not recognized, then it is true no power.

Okay, so no power---now what?

Let's make a short list of possibilities, and then use DEVICE HISTORY to guide our thinking.

No Power COULD BE:

  • Bad battery
  • Short anywhere on the board-water damage
  • Burned/damaged charging ic chip or usb protection ic from cheap charger usage or extremes of voltage/temperature
  • Water damage corrosion of charging coil
  • Mechanical damage to charge port or surrounding areas--can't charge battery
  • Environmental damage--corrosion--at the external charge port
  • Drop damaged CPU or Power management ic chip--cold bga joints under chip
  • Tool/fingernail damage near battery connector popping off a filter required for the battery main line.
  • Flexed board--internal damage to power line traces within the board
  • Extreme voltage or Heat damage to CPU or Power management chip

Any of these are possible, and as always---let HISTORY BE OUR GUIDE

To see how important device history is, take a look at this list, and just as an exercise---try for yourself to see if you can sort/eliminate some options based on these different histories.   1.) never been opened.  2.) Dropped in a sink and put in rice (boo!)  3.) Had a recent shattered screen replacement.   History is important, because with iPhone repair we have to be efficient.  It rarely makes sense to spend hours troubleshooting any iPhone, so we need to quickly focus on boards with repairable problems and eliminate those not feasible to repair.  When you're learning, try to see the device as telling you a story.  Look at the big picture and think about how the history of the device guides your search and helps you to efficiently sort devices that you can repair, and those you can't.
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Step Two: Troubleshoot battery.  The cornerstone of any no power fix is the battery.

With the history in mind to guide our thinking, we still will always start with the battery itself for phones.   One thing I've noticed in iFixit Answers is this common misconception "Well, I know it's not the battery because I just installed a new OEM battery."   Just the use of the word "OEM" in any discussion of cell phone parts is a red flag for low quality.  There are no OEM parts available.  Mama Apple puts her foot down about that.  You'll notice that quality parts sellers, both domestic and in China, do not use that term.   You'll only find "OEM" bastardized by eBay and Amazon sellers that are pushing out low quality parts to newbies who have yet to learn not to buy them there.

It is not uncommon for "new" batteries that are readily available for phones to have a few hundred cycle counts on them, or to be outright defective right out of the box.   Never assume that a new battery is a good battery.   Even if a battery is able to generate a 3.8 voltage to supply power, it ALSO has to be able to talk to the board and report the battery percentage and battery temperature data.  If these lines aren't working, the phone will spontaneously shut down.  

You can get some information on the health of a battery by connecting the phone to third party software like iBackupbot (google for download).  Comment below if you have a good way to get battery health information that you trust.

In our no power troubleshooting, if a known good battery (i.e. a battery that measures 3.8V across the positive and negative terminals with a multimeter set on voltage testing.)  does NOT start a no power phone, then that points to one of the board level defects.  

Before concluding that a new battery doesn't start the phone,

Make sure to prompt the phone to boot from the battery in several ways:

1.) Top power button

2.) Inserting charger after battery reconnect

3.) Overlay a new power button or dock connector and try again, just to make sure you don't have a simple component defect.  



Step Three: If a KNOWN GOOD BATTERY DOES NOT SOLVE, THEN ---> Troubleshoot BOARD LEVEL PROBLEM--->Microscope Evaluation--small component damage, or chip-level defect?

There are two kinds of board problems---small component and chip level defects.  Small components--like filters, resistors, diodes, capacitors--these are easy to replace.  They can be commonly sourced from donor boards, and plugged right back into their places.  Integrated circuit "chip-level" defects can be much more insidious.  They are usually the result of drop damage creating cold solder joints on a bga (ball grid array) ball that supports one of the black box chips on the board.  Alternatively, it could be a burned chip from an unprotected voltage fluctuation, or the result of extreme heat from a day on a hot dashboard.  

What do chip-level defects look like under the microscope?  They look like normal chips.  And that's the problem.  There is no quick and easy way to figure out exactly *which* normal looking chip is at fault.  And even if you did, sourcing those chips can be difficult.  And installing them?  Ugh---even to just get a bga chip off the board, you're left with a sea of black underfill that was cured to a non-removable hardness and used to help the board sustain the stress of stressed out John throwing Kate's phone against the wall when he reads a text from her new man.   The bottom line for chip-level defects? Micro-mini bga repair to replace the bigger ic chips is just not feasible.  Not for a phone.  

So that leaves the small component damage.  Pry damage, fingernail, plastic tool damage, screwdriver slips etc.    If you see visible damage, then that is great!  It is usually strong evidence that this IS the source of your no power problem. You should absolutely learn to replace these components from donor boards, or send your phone out for repair.

How do we distinguish chip level defects from small component damage?  By Microscope Evaluation!  This should always go hand in hand with every repair.
 

Step Four: If a known good battery does not work then----> Troubleshoot Charging System Problem

 

Troubleshooting the charging system:  Charge port or Board-level Charging circuit?

If a known good battery powers on the board then you're looking at a no charge problem.  
This can either be the actual charge port, or it can be board damage to the charging circuit.
The charge port only fails for a reason.  If it gets bent/broken pins---it has failed.   If it is green and dirty---it has failed. If it looks intact and still doesn't work when cleaned?  Then it is probably okay.

In an iPhone it is relatively easy to just pop in a new charge port/dock connector.  You don't even have to take the board out and fully install the thing---just overlay it and snap into its connector.  It is so easy there is no reason not to do it to test any no charge/fake charging problem.  We can't always really see inside the dock connector, so there may be damage/corrosion in there.  Go ahead and try a new dock connector any time your are troubleshooting a charging circuit problem on an iPhone.

But what if your device has a soldered in connector, like the Galaxy s3, iPad mini or Air, or Kindle fire?  

If you DO see damage to the charge port, that is great!  You have almost certainly found the cause of your no power problem.  Replace the port to solve.

 If there is NO DAMAGE to the charge port, no bent pins, it is not loose, and no corrosion---then DON'T REPLACE THE PORT.   The mini USB charge ports common on Android devices are pretty simple.  They are either intact or loose.  If the port is intact, replacing it is wasting your time--the charge port is basically a plain old wire, and if it looks good it is good.  In the absence of visible damage---the problem will be board-level charging circuit damage.

You can troubleshoot board-level charging circuit damage the same as troubleshooting the no power board damage above.  Do a microscope exam to look for any visible damage.  Since you've narrowed it down to the majority of the phone working ok, just not the charging system, then in this case it makes sense to consider heading out on the internet to find the schematic for the device and trying to devise a plan to examine and test individual component of the charging circuit.   This can become a time sucking rabbit hole, but sometimes it can help just show you where to look.  If you can find the damaged component, replace it, and hopefully your no power problem will resolve.  If you don't find visible damage, then you could be looking at a chip-level defect.

 

U2 charging ic failure: Special case

It is worth pointing out the special case of charging problems in lightning connector devices.  All of these devices--iPhone 5, 5s, 5c, 6, 6+, iPad mini, mini 2, iPad 4, iPad Air.... have a common point of failure.  The "U2 charging logic ic chip"  This chip is easily burned due to unprotected voltage fluctuations common to use of non-Apple chargers  (especially car chargers).  In the iPhone 5 where this defect is widespread, we will see devices that show one or more of these symptoms:

Symptoms of U2 charging logic ic failure:

  • Fake charging
  • No charger detect
  • Inability to charge a stone dead battery, but can charge a partially charged battery
  • Very rapid battery drain
  • Heat at U2 ic chip. 
  • Auto power on at battery reconnect
  • Inability to restore due to dropped usb connection
  • Some subset of  'blue screen' problems in iPhone 5s and possibly mini retina

The replacement of the U2 chip is a big ol' PITA.  The chip is encased in underfill and shares a border with the CPU in the iPhone 5.  Many talented microsolderers can replace this chip on a case by case basis, but as of now, it doesn't seem like there is a robust way to roll out a feasible general service to address this common problem.  So for now, U2 problems (at least in the US) largely go unsolved.

This underscores why it makes sense to pay attention to history and follow an efficient plan.  You don't want to get caught soldering in an iPad mini charge port to replace one with no visible damage, when the iPad mini was used with a non-Apple car charger----right?

Above: An iPad mini botched charge port job--this mini never needed a new charge port.  It's problem was a single filter next to the battery connector that commonly gets flicked off during screen replacement and causes the device to appear not to charge.  A quick microscope evaluation would have revealed this.

 

Case Examples:

I was prompted to write this post this week because of a few very different cases that came through the shop with  very different outcomes.  Let's look at how to handle these repairs in a practical setting of a repair shop.

CASE 1: Kindle Fire--botched charge port rescue.  

I had a device arrive from another shop for some rescue help on a Kindle fire charge port installation.  My job was to solder the charge port and to make some microjumpers to restore the function of two missing pads from a prior repair attempt.   I put in the connector and then found that the Kindle still didn't charge.  
I put in a new battery from another Kindle, and found that the Kindle did not boot from the known good battery.   I asked the shop if they were sure that the Kindle charge port had any visible damage to begin with, and they weren't sure.  

What went wrong?  
Here, this shop had made an assumption that if a Kindle had a no power problem despite sitting on a charger for a long time, that it must not be able to charge and therefore needed a new charge port.
This is not efficient troubleshooting.   What should they have done?

1.) Told the customer to just go buy an iPad.  Kindle repair?  Nah....

2.) Check charge port (since it is easier than checking battery).  

3.) If charge port loose--replace to solve.

4.) If charge port is not loose---Evaluate battery--is it dead?  If so, will Kindle start with known good battery? 

5.) If no:  Not Repairable.  Don't bother with a microscope eval of the board, because history says that if the device was never opened, this is going to be a chip level defect.

6.) If yes: Replace battery and confirm that Kindle can charge the battery to solve.   If not, chip level defect.

 

 

CASE 2: iPod Touch 4th generation---sudden onset of fake charging.  
My buddy Rich Clark of Computer&Phone Repair in Batavia, NY  picked up on a problem that I hadn't yet seen.  Rich does a great job on his customer intake form to document any pre-existing problems with any device that comes in for service.  He had an iPod 4th gen come in for a typical screen replacement, and from his form, he knew that it did not come in with a charging problem.

The screen replacement had a few typical complications, but ultimately at reassembly, he realized that the iPod was showing "fake charging" where the device will detect the charger and indicate that it is charging, but does not actually charge.   Rich did everything right with this plan.

1.) Evaluate charge port---no damage

2.) Evaluate battery---same symptoms with new battery

3.) Microscope board evaluation to look for physical damage----HISTORY points to a good likelihood of visible damage.  This was a complicated repair, lots of chances for physical damage.

4.) Rich scrutinized the board and found three teeeeeeny tiny components that were missing from an area of the board that is a common place to put a tool when separating the midframe from its adhesive.

We didn't know if these components had anything to do with the charging circuit in the absence of a schematic for this device.  Rich drove out and because of the history of this problem, repairing this damage seemed like a good bet to make to solve.    

5.) Replaced components from a donor board to solve.  iPod touch charged the battery fully--problem solved.

These examples highlight how important your thinking is when addressing charging/no power issues in iDevices.  Repair of mobile devices always is carefully balanced against just replacing the device.  By using history and practical approaches to troubleshooting, we can focus on the devices that we can save, and avoid uselessly wasting our time and repair dollars on devices that ultimately are not feasible to repair.

 

 CASE 3: iPad 4 no power/dead

Another repair buddy posted on a forum wanting to know who could get him an iPad 4 battery ASAP with overnight shipping.    Immediately, I thought "oh man, this is going to waste some time and money--it is U2."  From what you've learned here, tell me---Why would I think that?

Most of the time when an iPad 4 is going to come in stone dead it will arrive unopened.  This history eliminates any chance of 'technician damage' on the board, leaving only chip-level defects as a possibility for a no power/no charge issue at the board level.   

I knew that my competent friend would have already ruled out the easy to replace charge port before thinking about seeking to have a new battery overnighted.  Most solvable charging problems for iPad 4 will be a damaged charge port, and I guessed that he tried a new charge port and it didn't solve.    

Why not just a bad battery?  The likelihood that the battery just dropped dead one day is low--the iPad 4 isn't that old.  It would be more typical for the battery to decline over time.  The customer would have come in with a working iPad and complaining about poor battery performance.  The shop owner would have ordered a battery and told him to come back and schedule installation.   A stone dead iPad 4 is an excellent candidate for U2 ic damage--which would create a crisis.  One day the iPad is fine.  The next, the chip gets burned and it has a sudden onset of no charge.   The iPad runs down and at the end of that day is a brick, trapping all the data that is on it and creating a sense of urgency.

A new battery might bring the iPad back enough to suck some data off, but it is unlikely to solve the underlying problem.  I advised my buddy to invest in a DC power supply to manually force a little charge in the existing battery to get the data off and troubleshoot no display vs. no power vs. no charging.

A few days later I get a call asking about U2 ic replacement....


This is another example---take in ALL of the information, use the HISTORY, think about the big picture and this will help you develop your own 'crystal ball' based on experience---this will guide your troubleshooting, save you time, save you money, and keep your business sustainable.

 

 

 

 









 

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Great post as always, you and Luis Rossman have two of my favorite blogs.

Thank you for the great article! Your work is inspiring. I have learned some great tips from you and look forward to more. Thank you!

I really wish someone would do a walk-through, probing and testing.
Jesus Christ that would be so great. Not a single video on this planet for that. Plenty of people show they can change the chip. Thats great, me too. But before I go removing stuff, I would like to know by testing that with certainty, that is what needs to be replaced. What if it were a different component along the line? Just change the U2 IC! WRONG ANSWER. Lets all point to the U2 and say how hard it is, or look I can do it. But how do we test it? Louis is great, but he refuses to teach this. No one will. What gives?

@Tony
Cell phones are different than motherboard repair. You could scratch away at the underfill to reveal the traces coming to and leaving the U2 chip, you could apply oscilloscope probes try to see if there was a specific signal that was missing or different than a normal signal coming out of U2. You could in theory look for errors related to charging logic in the real time logs.

But in general, that is a lot of work, when the fact is that a phone that A.) Has had non-Apple charger usage. B.)Is showing one of the many U2 charging problem symptoms despite a new battery and charge port and C.) Has no other problem, like recent drop or water damage. and D.) Can start from a good battery but not charge it-----this is enough evidence to diagnose a likely U2 failure. Why? Because we know U2 gets burned up by chargers and other chips really don't. At that point your most feasible path is to replace the chip or discard the repair if you're not able to.

When you go to the doctor with a sore throat, the doc will use all available clues to figure out quickly what *most likely* is going on. Do they actually culture your throat, send it to microbiology to determine the exact organism and then apply a series of antibiotic tests to determine the exact antibiotic that will be most effective? No. Because that's not practical.
Same thing for board repair. Practical board repair says you pull the trigger on U2 replacement as described above. It is not practical to prove beyond a reasonable doubt that the only thing is U2. I don't know if you'll ever stop back here, so I will cross post this on your similar YouTube comment.
Cheers,
Jessa

Man, if I had a buck for every time a customer asked me to change the battery or charge port of their phone to resolve their symptoms when they misdiagnosed their problem (thank you Dr Google), I wouldn't have to repair anything. The dollars would flow on in! lol

"My mobile electronic thingy won't charge, so I need a new charge port"

Slow down there turbo. Let's back up and get some history here. Yesterday, while fixing this nice young woman's iPhone screen, she brings up how her iPad won't "charge" and asked how much to replace the battery - you know, because it's "old" (iPad 3). I asked what charger she's using. She produces what appears to be a cord that came with the iPad. I asked where the wall cube was. She runs off and comes back with..... a 5W iPhone cube! ...then says, "it's been plugged in all night and went from 5% to 7%. I asked where her iPad wall cube was. She pulled it out of her purse and said, "I bring it to work with me to charge my phone faster".

I had to really restrain my ing and sarcasm - because she really didn't understand, she's a nurse, and I'm a nurse and I'm really trying to not sound like a jerk know-it-all when explaining why the customer's diagnosis is incorrect. I politely explained the difference between 5W and 10W chargers and how they work with various devices and that using a 10W charger on a phone won't produce a faster charge, but using a 5W charger on an iPad will certainly charge the battery at a rate so slowly that you'll assume the device MUST be faulty.

Hi. I charged an iPad mini overnight and in the morning it was dead. No response for holding down the buttons, charging with another charger or connecting to computer. Stupidly enough I did not suspect the charger, so now the other mini died the same way. Looked closely on the charger and saw "able" instead of Apple... Can it be the U2 charging chip?

Hi. I have a problem with my iPad mini on board charging pin. 2 pin lifted out from board. Can it be repair. How?

Hello , great work,
iphone 5s when apple logo appear then the lcd no image when i plug in to the laptop doesn't recognize it. So we have power because backlight work but not image and the laptop doesn't recognize it .. ?????
any help...



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