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Advice on PCB repair iPhone 7. Anyone?

Hi,

Question for someone a little more on the micro soldering / PCB repair side of things.

Re iPhone 7 (intel) - Attached photo of my measurements and notes.

Phone stuck in boot loop, not charging, not registering in itunes. Getting into repairs so trying to fix it but finding it a bit difficult to wrap my head around. Getting there thou.

Tried so many things, took diode measurements for J4502 and other parts. Went through PCB to try and find a short of a fault somewhere, no luck.

I did notice some strange readings on J4502 pin 24,26, 30, 32, 36, 38. Got double the reading I should of got up in the 800, supposed to be 485 for all.

This led me down the line on the iPhone schematics chart to L3901, L3902 and L3903. All those had way high readings in diode mode so does that mean they are all fried??

Will they lead a phone to boot-loop and not charge?

What other pins should I check that would relate to a phone behaving like this? Would it lead me to find the culprit which is responsible for this happening?

Is there a way I could test the AUDIO IC with a multi-meter to find out if it is responsible?

Or could it be the base band pmu? all the capacitors around it seem to be good when measured in diode mode.

Any advice from someone experienced would be greatly appreciated.

I am learning so much on this phone and am confident of finding the solution with a little help and guidance

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P.S Just noticed C1403 is measuring only 0.04v. Thats too much resistance right? way too low. shouldnt it me about 0.350 - 0.450v? Please correct me if I’m wrong

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It is hard to diagnose this problem over the internet.

·         Have you ruled out parts by putting it into a known good housing with good battery?

·         Are you using your multimeter correctly?

·          Red probe on ground?

·         What is the history of the phone?

·         Has it had an audio IC repair done?

·         Have you put it in DFU mode and tried a restore or recovery?

·         How much current is it drawing on prompt to boot?

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Hey mate, yeah I understand but just trying to get some input on how to diagnose and find the culprits responsible.

Can you confirm should the readings on J4502 pin 24,26, 30, 32, 36, 38 be so high in the .800's?

I am trying to rule out the IC's like the BB and the Audio IC. Trying to find a way to do that with the multi-meter.

Answers to your questions:

1) yeah I have no luck.

2) Yeah using multi-meter correctly.

3) Yep red probe on ground, confirmed I had a proper ground too.'

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4) Phone had no problems at all nor did I have any major issue, bought it at Apple in Sydney about 3 years ago. The only small thing that started happening was my ear speaker was very faint, I work in construction so I thought it might have been dust getting into the mesh covering the speaker. Other than that phone was in good condition, didn't have any major falls or anything as such. About a year ago I had the phone in my back pocket and was getting into a car and sat on it. It slightly cracked the back housing, was slightly bent but screen did not shatter nor crack. About a month ago I thought I'd swap out the back housing into a non cracked on so I did, also at the same time replaced the speaker and flex. Put everything back into the new housing and from that moment on the phone had boot loop issues, did not charge, no charging logo when plugging into lightning plug to charge & not registering in itunes.

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I check for cracks or broken motherboard but it all looks fine. Only thing I found was a bit of the motherboard was broken on the very top left corner where the screw goes, there aren't any components there. I marked up a photo which I attached so you can see. I visually inspected the fault line and all seems fine. But like I said im trying to find a way to inspect the BB and Audio IC on the fault line with multi-meter.

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5) No it has not had an Audio IC done, non has it had any other repairs. Phone had no previous issues.

6) Yep tried DFU mode and tried a restore or recovery but itunes downloaded new software installed it and at the end when it went to update everything and finish an error came up saying the phone could not be restored or recovered.

7) Will have to measure with multi-meter how much its drawing and let you know. It is not even turning on now nor charging so I think it flattened the battery. Will take battery out and put it in another iphone 7 so it charges up and will try again.

Thanks heaps for taking the time to comment, I appreciate it a lot.

Cheers

Tommy

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@Tommy Duris It is hard to measure the baseband CPU. You can measure around the baseband PMU and check for shorts. The Intel boards are not known for baseband shorts only the Qualcomm are. If you try a restore with 3uTools you can see where it fails.

It is also hard to check the audio IC without removing it. Have you tried just booting the phone with only the LCD connected?

If the phone suffered a bend it could be a lot of things. Tristar, Nand, baseband, audio IC or a lifted resistor on an data line. Try 3Utools first and see if it fails on updating baseband.

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