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Go Back   GSM-Forum > GSM & CDMA Phones / Tablets Software & Hardware Area > iPhone ,iPod & iPad (Apple Inc. Products) > iPhone, iPad, iPod Hardware Repair

iPhone, iPad, iPod Hardware Repair Hardware Repair discussions for iPhone, iPod , iPad & Apple Products, help, guides.

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Old 05-27-2011, 15:05   #1 (permalink)
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3GS, where is the charging fuse please?


Hi everyone, I need some help please with this iPhone

It's the 3GS 16GB, it does not power up, and does not charge, and it is not recognised in iTunes, it is basically dead!

this has happened after a cheap copy chinese wall charger was used to charge the phone, this is 100% sure because it has done the same to my wife's iphone!!

I have tried to press and hold home and power button, also tried, holding the home button and connect to iTunes, but Nothing!!

Anyway, I have opened it up, dismantled it, tested the battery with a voltmeter and it shows 0.12V, a good battery should show 3.7V


After fitting the new battery, the iPhone switched ON, battery showing 40%, but it still does not charge and is not recognised in iTunes

After 1 hour, same problem, iPhone does not switch on, does not charge, opened it again, tested the new battery and it shows 0.14V, so it is drained!!

i have bought another new battery and charging port/dock, refitted everything, same thing, iPhone switch ON but no charge.

I have tested the battery fuse and it shows continuity so it is OK, but i don't know where is the charging fuse on the 3GS ???
does anyone have pictures of this fuse?

What should I do next?

Thanks in advance
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Old 05-27-2011, 16:06   #2 (permalink)
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hello, down, near the antenna connector, on the right hand side, just close to the metal protector, you can see a green component, 2mm or so. that is the fuse.
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Old 05-27-2011, 16:43   #3 (permalink)
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Try change charging ribbon
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Old 05-27-2011, 18:31   #4 (permalink)
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Quote:
Originally Posted by ifonman View Post
hello, down, near the antenna connector, on the right hand side, just close to the metal protector, you can see a green component, 2mm or so. that is the fuse.
Hi, thanks for your reply
i have checked the battery fuse, but i am looking for the charging circuit fuse, apparently there is another one?
look at photo on my 3GS motherboard, the fuse circled in red is the one i have tested and it is OK,
my question is: where is the other one??
Thanks
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Old 05-27-2011, 18:31   #5 (permalink)
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Quote:
Originally Posted by ong3822 View Post
Try change charging ribbon
Hi, which one is that? i already changed the complete dock assembly, is that not the one?
Thanks
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Old 05-27-2011, 19:22   #6 (permalink)
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The green component isn't a fuse, but a very low resistance resistor, used for current sensing. Anyway, if the phone switched on with a new battery, but it wouldn't charge, then your problem lies in the charging circuitry. My 3GS failed in a similar way, although iTunes still recognised it. The original battery had died badly, almost completely burning away one of the metal tabs that goes into the battery cell itself, and this had damaged the 338S0768 power management IC located underneath the top metal cover.

Interestingly, after changing the PM IC, the phone worked for a while then crashed and was stuck in a boot loop and giving error 1611 when I tried to reinstall the firmware. Nothing I did seemed to help, so I left the phone assembled but switched off, with battery inside it and connected, for about 5 weeks while I did other things. When I decided to try again with the phone, it came on, firmware reinstall worked and the phone is now working alright and has been for a week now. I can only think in the 5 weeks, the power drained absolutely and something reset?

Very odd things these iPhones, and knowing whether a fault is damaged hardware or simply 'confused' hardware is difficult. I can't pretend to understand any of it when leaving it for weeks cured the fault... Of course, the Apple engineers who designed it could probably explain all these odd behaviours and effects, but long gone are the days of manufacturers giving technical support. Sad world we live in. So, we can only continue guessing.

Before changing the PM IC, since you don't have iTunes recognising the phone, there may be no connection whatsoever from USB. So, check these two inductors I've circled. The USB input passes through them before going to the rest of the logic board.

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Old 05-27-2011, 21:14   #7 (permalink)
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Hi chapster
Thanks for this information
The inductors I have to check then is the one you circled in the bottom of the picture? The one at the top I already tested with an ohmmeter and it showed continuity so I presume it is ok?
How do I properly test the one you circled? Looks a bit different than the other one.
Also, did you change the PM IC yourself? Was it a hard job? And how much is a replacement?
Thanks and very sorry about all these questions!
Best regards

Last edited by benaknoun; 05-27-2011 at 21:23.
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Old 05-28-2011, 01:59   #8 (permalink)
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Ask as many questions as you like, it's the only way to find these things out and I do the same. There are 2 inductors within the circle I've drawn, they are the ones that need to be checked, and they should read short-circuit when measured. They pass the 5V USB supply directly to two MOSFETs which feed it on to the PM IC and elsewhere. I have heard of the MOSFETs failing as well, which I think gives the same symptoms as you have now.

The top current-sense resistor should read short as well, so that's okay. Test the inductors on the resistance (ohm) range of a multimeter. They're very small, so a bit tricky to get the probes into place, but can be done.

I did change the PM IC myself, but it's quite a job. My family trade is electronics repair, and as such, although I no longer work in the field, I still have soldering stations, a hot-air station, etc., and so used what I've got to do the job. Main difficulty is removing the old IC, as they use black epoxy underfill to help adhere the IC's body to the board, giving it extra strength against board flex. Also, lead-free solder has been used which has a higher melting temperature than traditional lead solder, so removing the IC without a PCB preheater means using a very high temperature to melt the solder, and applying upward pressure the whole time because the glue is weakened by heat but still holds on, meaning you can't tell by feel when the solder has melted, but must just apply pressure till eventually the glue bond breaks and the chip flips up.

Then the area must be cleaned of epoxy and old solder using lots of flux, desoldering braid and gentle but firm pressure with the iron as you move the braid around. New IC must be re-balled using a stencil which I bought from China (bought 10 with aim to sell the other 9), and that can then be soldered into place using hot-air station at a lower temperature if you use leaded solder paste, as I did.

It's a small IC with very fine pitch solder pads on it, and that makes alignment a careful process, but it went alright for me. Main problem was as detailed above, which seems resolved after 5 weeks of being left alone. I don't understand the mechanisms involved since I'd left the battery disconnected for days beforehand, but something happened and now it's working and charging normally, and most importantly holding its charge. Before the repair, not only would it not charge, but when I fitted a new battery, it discharged from 85% to dead in one hour.

The IC was also bought from China after a week of emailing lots of different sellers and eventually getting the best price for the IC and shipping to the UK. I think the total price was 25 or thereabouts, but I'd have to check as the payment was in dollars. I bought two in case of me damaging one, again with the aim of selling the 2nd one if it wasn't required.

First though, try to find out if anything else is wrong. I don't know if PM IC failure can cause the phone to not be recognised by iTunes, mine didn't have that trouble, but failure will occur in different ways, depending which section of the IC is actually destroyed, as it has many functions. There is a post on here titled something like 3GS PMIC voltage hints. Find it and use the voltage reference points as a comparison with yours when the USB connector is plugged in. You may find voltages are missing, and the location of those missing voltages can then be tracked back to see what the likely cause is. Post the information on here, and then I or others can check the schematics and help.
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Old 05-28-2011, 03:49   #9 (permalink)
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Quote:
Originally Posted by chapster View Post
Ask as many questions as you like, it's the only way to find these things out and I do the same. There are 2 inductors within the circle I've drawn, they are the ones that need to be checked, and they should read short-circuit when measured. They pass the 5V USB supply directly to two MOSFETs which feed it on to the PM IC and elsewhere. I have heard of the MOSFETs failing as well, which I think gives the same symptoms as you have now.

The top current-sense resistor should read short as well, so that's okay. Test the inductors on the resistance (ohm) range of a multimeter. They're very small, so a bit tricky to get the probes into place, but can be done.

I did change the PM IC myself, but it's quite a job. My family trade is electronics repair, and as such, although I no longer work in the field, I still have soldering stations, a hot-air station, etc., and so used what I've got to do the job. Main difficulty is removing the old IC, as they use black epoxy underfill to help adhere the IC's body to the board, giving it extra strength against board flex. Also, lead-free solder has been used which has a higher melting temperature than traditional lead solder, so removing the IC without a PCB preheater means using a very high temperature to melt the solder, and applying upward pressure the whole time because the glue is weakened by heat but still holds on, meaning you can't tell by feel when the solder has melted, but must just apply pressure till eventually the glue bond breaks and the chip flips up.

Then the area must be cleaned of epoxy and old solder using lots of flux, desoldering braid and gentle but firm pressure with the iron as you move the braid around. New IC must be re-balled using a stencil which I bought from China (bought 10 with aim to sell the other 9), and that can then be soldered into place using hot-air station at a lower temperature if you use leaded solder paste, as I did.

It's a small IC with very fine pitch solder pads on it, and that makes alignment a careful process, but it went alright for me. Main problem was as detailed above, which seems resolved after 5 weeks of being left alone. I don't understand the mechanisms involved since I'd left the battery disconnected for days beforehand, but something happened and now it's working and charging normally, and most importantly holding its charge. Before the repair, not only would it not charge, but when I fitted a new battery, it discharged from 85% to dead in one hour.

The IC was also bought from China after a week of emailing lots of different sellers and eventually getting the best price for the IC and shipping to the UK. I think the total price was 25 or thereabouts, but I'd have to check as the payment was in dollars. I bought two in case of me damaging one, again with the aim of selling the 2nd one if it wasn't required.

First though, try to find out if anything else is wrong. I don't know if PM IC failure can cause the phone to not be recognised by iTunes, mine didn't have that trouble, but failure will occur in different ways, depending which section of the IC is actually destroyed, as it has many functions. There is a post on here titled something like 3GS PMIC voltage hints. Find it and use the voltage reference points as a comparison with yours when the USB connector is plugged in. You may find voltages are missing, and the location of those missing voltages can then be tracked back to see what the likely cause is. Post the information on here, and then I or others can check the schematics and help.
Hi Chapster
Wow, that is amazing! you really know your stuff and you know what you are talking about, thanks very much for all the info, really appreciate your help.

i have tested the top current-sense resistor and it shows 0 ohms resistance, i have also checked the two other inductors withing the circle you have drawn, and they also show 0 on the ohmmeter, so this means the problem is not there? am i right?

This means i am stuck and out of luck, because to be honest with you, after you described the job you have done to replace the PM IC, i put my hands up, i can tell you that it is not for me, too complicated, and if i try i will make things worst, i do not have the experience nor the tools required such as the hot air station...etc
I would love to learn how to do it, but maybe it is not the time and not on this motherboard.

Anyway, i just wanted to add another info, when i fitted the new battery, i forgot to mention that, after switching the iPhone ON, it displayed a yellow warning triangle on the screen, saying: " Temperature, this iPhone has to cool down before it can function"
Not sure if this gives any hints??

Like i said in my first post, i have two of these iPhones, i will test the fuses on the second one tomorrow and post the results.

So, can you give me a conclusion for this iPhone please, is the problem with the PM IC ? any further testes i can do? is it worth going further?

Again, thanks very much for your help
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Old 05-28-2011, 04:18   #10 (permalink)
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Just charge the battery apart of the iPhone
Assemble the pcb to it and turn it on!

Now put your finger on PM IC, if it's overheat then you need to change it

BR
Max_B
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Old 05-28-2011, 13:56   #11 (permalink)
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Quote:
Originally Posted by Max_B View Post
Just charge the battery apart of the iPhone
Assemble the pcb to it and turn it on!

Now put your finger on PM IC, if it's overheat then you need to change it

BR
Max_B
Hi, thanks for your help
what is the best way to charge the battery apart of the iPhone please? is there a special charger for this?
once the battery is fully charged, i can fit it and install the PCB on top, to turn it on, obviously i can't put the screen? is that right?
Sorry but i am a newbie!
Thanks
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Old 05-28-2011, 14:30   #12 (permalink)
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try tomclean the board with isopropilic,alcohol, and tooth brush, then reconnect thembattery and try again, post results
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Old 05-28-2011, 14:37   #13 (permalink)
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Quote:
Originally Posted by ifonman View Post
try tomclean the board with isopropilic,alcohol, and tooth brush, then reconnect thembattery and try again, post results
Hi, i don't mean to be rude, but are you sure this is good?
Thanks
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Old 05-28-2011, 15:41   #14 (permalink)
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yes, is a good tecnic, i have used it several times, and everybody uses it to clean boards that have sufferd water damage.
i think that your board has a shortcircuit. do not be afraid.
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Old 05-28-2011, 15:46   #15 (permalink)
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Charge the battery with a power supply!
Connect crocodiles to battery terminals + and - and its ok.

Cleaning shorted boards wont fix

BR
Max_B
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