Fourth generation iPhone. Repair is straightforward, but the front glass and LCD must be replaced as a unit. GSM / 8, 16, or 32 GB capacity / Model A1332 / Black and White.

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Help to restore iPhone 4 charge circuit please.

Hi

The iPhone charged at first, then one time after it draining completely I turned it on to find that it wouldn't charge, when plugged in the % would drop. To add to this when shut down it would now stay hot and drain.

I replaced the battery, dock connector and still no charging. Was going to get it sent off for a new power IC until I decided to open the motherboard up.

Under the metal casing I found a lot of green gunk/corrosion which I assume was from water damage.

This was located at the bottom near the antenna and blue capacitor but inside the charge circuits.

I cleaned this out with a toothbrush a alcohol, first it didn't help, but after leaving it soaked in alcohol for a bit and drying it it began to charge again!!

It now works, but charges incredibly slowly and is quite hot. Is there a way that I can make sure the corrosion doesn't come back and a way to hopefully speed up charging? It's all hardware related.

Many thanks.

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Thanks for the reply I've added pictures. The green is where it was all gunky. And FYI the crack in that chip wasn't there until I took it apart and accidentally did it so it's got nothing to do with the issue. And yes I removed the EMI shield.

Also it drained again today and won't charge, must have build up corrosion again...

Thankyou

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Leo, looks like you have at least one broken component. L9 looks cracked. That is 1.5UH-2A-126MOHM VLS252012-SM coil. The other bigger issues might be U11_RF which is a RF power regulator MAX8839L and is directly related to the charging circuit. You could check the components with a multimeter and see what you get. It also still looks like a bit of corrosion. you do want to remove those EMI shields and clean everything properly and double check that area for more missing, broken components. Hope this helps, good luck.

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Thank you so much I have been looking for a clever electronics person for a long time. I have tested the parts with a multimeter and they all seem to be fine, apart from the fact that they're covered in some kind of oxide which makes it hard to contact. I can tell you that the whole area (from the U11-RF down) is almost too hot to touch when when the phone is off and on.

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Is there a component that could be bypassed to test if it's the one that's broken? I don't want to burn anything out by making a jumper on the wrong component.

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I have no issues with any RF parts of the iPhone does that mean that U11 is most likely fine?

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No it does not. U11 has a big part on the power management. that is why it could be getting hot. Also, L9 is a coil that receives power etc. by being broken, it can and will also generate plenty of heat. I'd start off by checking the smaller components for continuity and see what you get. I will add the schematic and pinout of U11 with my original answer. Pay particular attention where the Batt VCC circuit connects to the IC, you will see the importance of the IC's function.

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Right OK I will do, thank you.

The L9 coil is fine as far as I can see it was just the plastic that broke off as I scrubbed the area. I'm confused how it worked for a bit and then stopped, makes me think a large part hasn't broken but don't really know.

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heat = a short.

Phone is not going to work well with a short, and excess heat will damage other components. You have to find and fix the short.

Which component is the source of the short? The one that is the hottest.

One way to find it is to use your lips which are really sensitive. Another way is to spray that part of the board with a freeze spray then see which component melts first.

In any event, you know you had/have corrosion. Any component that is/was discolored or burned could be the culprit. A component can look visually just fine, but not function electrically as designed. Just like a loose lightbulb may light up for a few minutes in the right position, your phone temporarily was able to charge---you still need to screw that lightbulb in if you wanted to actually be able to use the device.

If you find the likely source of the short, you can remove that component and see if the heat goes away. Replace it with a good one.

Of course this, like the battery connector repair, requires specialized skill in microsoldering. You really wouldn't be able to achieve a successful result (in my opinion) without experience, a stereomicroscope, a 0.2mm variable temp soldering station, and the low melt solder that you said you didn't have ;)

But, everyone has to start somewhere---give it a try and let us know how it works out!

jessa

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It is very frustrating trying to solder the connector on with only and iron and some high melt solder. In fact I ripped off the solder plates by accident and coated the tiny components in solder, cannot get it off now!

There are 6 small copper contacts to the right of the charge connector which don't actually touch anything. One of these came of, is that a problem? Also how on earth are you meant to get unwanted solder off the little fuse looking components?

Thanks very much. It seems the more I try to fix the more I break

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yes--this is why I'm constantly spamming the board with 'if you need a professional to help get your repair back on track give me a shout' You're right--it is one of those things that takes quite a bit of failure to perfect

The copper dots are not important--just don't bridge them.

You absolutely can remove bridging---you need a lot of flux--a kind that has a little bit of tack to it. If that's not enough, apply some copper solder braid along with a lot of flux.

Your biggest problem are the solder pads---if these are gone you'll have to find another way to restore continuity from the battery connector pins to the next component on the line.

Again---stereomicroscope, 0.2mm variable temp soldering station, and plenty of experience microsoldering are required for this repair---you can get by without the low melt solder, but that would make it a whole lot easier.

There are a lot of very affordable places online that consider iPhone 4 battery connector a very straightforward fix--even with missing pads.

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Ok first I'll buy some flux give it a go. If not it would be great if I could pay you to do it. However touching the 2 battery terminals onto the jumper location above the battery connector still doesn't work... I'm wondering what could have broken if the polarity was touched on wrongly for a split second? :(

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What's the first part that would have burnt out in that event is what I need to know. I'm really messing it up but learning at the same time haha. Thanks

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After scraping away at the unwanted solder for hours I managed to get the iphone to turn on again just holding the 2 contacts on with crocodile clips. Fixed that problem but accidentally knocked off the blue capacitor which is responsible for the cellular antenna... another job haha.

Is it important to have the 2 middle contacts or are they just for the temperature sensor?

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Leo will be eternally grateful.
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