Fifth generation of iPhone. Repair of this device is straightforward, and requires screwdrivers, prying tools, and patience. GSM/CDMA / 16, 32, or 64 GB / Black or White.

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Won't turn on and logic board gets hot after power button fix

Good day everyone,

My tiny-actuator-helper disappeared from the power button and I had to remove the logic board to get to it for the fix.

Upon reinstallation of everything in the correct locations and in the correct order, I turned on the phone via connecting to power.

All was well for about 20-30 minutes, but while playing music through car stereo, the phone turned off and won't turn on anymore. There is no sign of life in it, except for unusual heat in CPU area.

Whenever I plug it into power, it heats up right around the processor area, but I can't tell where exactly. If I unplug the battery, the heat generation stops. Then if I plug in the battery after it cools off, nothing heats up. When applying power through a cord, it starts to heat up even after I remove the cord until the battery is disconnected. I haven't tried powering up via the power button as my fix needs to set overnight.

I have no Idea what in the vicinity of the CPU could be causing the overheating or why. Any and all assistance is greatly appreciated!!!!

Kind Regards,

Attila

Answer this question I have this problem too

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Upon reassembly just a few hours after initial symptoms, I was able to attempt a startup via the power button, but only got the same symptoms as before: no sign of life but for heat from CPU area.

Anyone have any idea what could cause such symptoms?

Also, anyone know where one might find a new logic board?

Lastly, if I do end up swapping logic boards, can the data be transferred over somehow?

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Attila, when you say " When applying power through a cord, it starts to heat up even after I remove the cord until the battery is disconnected" where do you plug your iPhone in? Wall charger, computer, custom charger?

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Application of power is via any cable method, including wall charger, computer USB, and car stereo USB. If there is any power-up trigger (button or charging cable), it starts to heat up and doesn't stop heating up until the battery is disconnected. I didn't try to find the equilibrium temp for fear of damaging the components, but a laser thermometer read 110F on the backside of the logic board.

Thanks

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I am thinking that you are having issues with the charging circuit on your phone. Wondering if the charging IC or coil are generating the heat......

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Interesting. I took a look at the 4s teardown on this site as well as googling it, and it didn't reference the charging IC or coil. Where might those be on the board?

And does replacement of these require unsoldering and resoldering? All I have is a standard 25 W Radiohack soldering iron. I never had a good enough reason to invest in an expensive soldering station, so my soldering capabilities are a bit limited.

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So the phone powers up when connected to power?

If tht the cause I would start by trying a new battery which is probobly your problem..

It's a bit early to start thinking about a new logic board

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Thanks for the reply.

Upon introduction of any trigger to power up (i.e. power cord connection or depressing power button), the only result is the heat building on the logic board near or from the CPU. I don't know the origin of the heat, as I can't precisely measure temperature, nor do I have a schematic of the electronic design.

It's baffling that between disassembly, and careful reassembly, it went from operating fine (with the unrelated exception of the power button) to turning off and refusing to power up. I opened it up again and made sure everything was put back correctly, but found nothing amiss that might indicate what had changed and caused the problem.

Is electrostatic shock a concern in phone circuitry? I have seen and read about people routinely working on phone and ipod logic boards without taking static shock precautions. Just a thought.

Anyway, I appreciate your suggestion. If I'm wrong, I can admit it, but with current indications, I believe the battery to be fine.

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You can't be sure that you never damaged the battery I would try a new 1.

Try new battery to rule it out.. That's all it could be

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Sorry and what u mean with current indications?

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Sorry! I was referring to time not electricity! "indications at the moment" would have been a better choice of words.

With regard to the battery aspect, what are the indications of a bad battery? I'll google it, but would like your reasoning as well if you don't mind. I've never observed a bad battery do these things, but of course, I usually don't pay close attention to that which rarely fails, so I'm a novice at battery diagnosis.

Thanks

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Well your saying the phone isn't turning on

Anybody's first troubleshoot is replace the battery

My reasons are having maybe 30 people since I starting repairing come in with phone not turning on an new battery sorted this every time

Hope this helps you out

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A hot spot on the board equals a short in my opinion.

As silly as it seems, one method of pinpointing a short is to remove the emi shields and power on the phone and use your lips to locate the hot spot.

You may never know the 'why'--heat itself can generate a short, perhaps from a defective battery, as can drop damage, water damage...you mention needing to wait before using your replaced power button--that is unusual--did you use some kind of glue in the phone?

In any event, plugging in a connector or hitting the power button prompts the phone to boot. Starting the electron flow in this way will run them through the path of least resistance, ie short circuit, ie generate heat, until battery disconnect.

Repair--finding a short is honestly a pain. You really wouldn't want to go anywhere near an iPhone with a conventional soldering iron. Some folks have success with the "poor man's reflow" ie an oven or hot air gun to attempt and get the solder balls under the chips to briefly experience 250 temp to melt in their place and hopefully "unbridge" and cool down back in place magically making just the right electrical contact. Very easy to give too much heat and irreparably damage components.

Good luck--if there is important data on it you might want to seek professional help. There are a few folks out there that specialize in this kind of thing.

Jessa

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Thank you Jessa.

I put a tiny dab of jb-weld on the underside of the metal power button to replace the missing actuator-helper, and the button mechanically operates good as new, despite the board not wanting to play nice. It didn't contact any other components besides the metal of the button before hardening, so that couldn't have caused the issue.

I wouldn't dare attempt a repair with a conventional soldering iron, I just don't know how a charging IC or coil might be replaced, so was asking about that.

With regard to seeking professional help, are there any recommendations for who to call?

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You likely installed the wrong power button cable on the phone like maybe a gsm in a verizon phone or vice versa. I have had these come in the store after home repairs.

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Attila will be eternally grateful.
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