The Apple iPhone 5s was announced on September 10, 2013. Repair of this device is similar to the previous models, and requires screwdrivers and prying tools. Available as GSM or CDMA / 16, 32, or 64 GB / Silver, Gold, and Space Gray.

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Trying to repair a 5s - Running into issues with diagnostics

Hello, I am trying to repair a 5s for a customer.

The phone does not turn on They have been to an iphone repair facility previously who mentioned that it needed a u2 replacement

My diagnostics attempt.

* The battery was dead,

* I charged the battery and connected the 4 terminals as shown in the picture and the battery

* I pressed the power button for about 30 seconds

* The phone did not turn on and became very hot and 2 generic locations on the board

Is there any other way I can diagnose the board or make the iphone turn on ?


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What you're describing is a U2 (Tristar) chip issue. If you replaced the charging port and put in a good battery and the phone doesn't turn on or charge then the U2 chip needs to be replaced which is underneath the shielding were it gets very hot that you mentioned in your picture. It requires a skilled person that knows microsoldering to replace the chip. I hope this helps you answer your question.

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I read somewhere that the bad U2 prevents the phone from charging.

Will it also prevent the phone from turning on when connected to a charged battery ?


Yes. I just got a iPhone 6 that the customer stated would not turn on or charge. Checked charging port it was good. Checked battery and it was bad, But after replacing the battery it would intermittently charge at times and the battery quickly died. Replaced the U2 chip and now the phone is working perfectly with new battery.


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