Why is the unit not turning on?

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iPhone 6

这款4.7英寸iPhone于2014年9月19日发布，是iPhone 6 Plus的缩小版。

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Tuohang Zeng @zengtuohang

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发帖于: 2017年5月24日

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Why is the unit not turning on?

I fixed the sensor flex PCB and after that, it was fine. But after I put the unit back, I realized I forgot to put the rubber holder for the ambient light sensor on, so, I put it on and after that, the phone will not turn on anymore. On that same day, I was able to detect the device on my pc and charge(?), but after a few days, it will not turn on at all and pc won't be able to detect it. I checked the voltage on the battery, it is 2.95V. Any suggestion of how to fix it? I am only fixing phones for friends and I don't have a ton of equipment. This is actually the first time encountering such problem. The other phone I fixed along with this one was fine.

Maybe the battery's problem? I'm not sure. The screen and touch and touch ID are fine when I placed the whole assembly on another working phone.

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BurnieG @burnieg

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I do believe 2.95v from the battery is to low to power on the phone. It would require closer to the area of 3.4v to power on the phone. So it could possibly be a failing battery. It may be a number of things but it could not hurt to start by trying another battery first as the one you have will not power on the phone due to not enough voltage being supplied to the motherboard. May also be the charge port is damaged or needs cleaned and your battery has discharged below the required voltage to power on the phone due to a damaged charge port.

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Well to be exact at least close to or above 3.7V for the phone to power on. Could be something heating up on the board causing a short to drain the battery quickly.

由 Ben 完成的 2017年5月24日

Yes could be a short. I was playing with my DC bench top power supply and it was with the iPhone 6s not the 6. It boots the phone to the lock screen at 3.5v. The iPhone 6s will turn on but not boot at 3.2v. Most phones that have a battery with a nominal voltage of around 3.8v boot at about 3.4v to 3.5v on my power supply. Thanks for the comment though as I don't have a iPhone 6 here I can play with that with take more than 1v before it trips my power supply due to a short in the motherboard.

由 BurnieG 完成的 2017年5月24日

I charged the battery to 3.9 now with a charger. And it still won't turn on. Any ways to back up the whole system, since the data is the most important part. Thanks! It might be because of a short. Now the battery basically stays there.

由 Tuohang Zeng 完成的 2017年5月24日

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Well to be exact at least close to or above 3.7V for the phone to power on. Could be something heating up on the board causing a short to drain the battery quickly. — Ben
Yes could be a short. I was playing with my DC bench top power supply and it was with the iPhone 6s not the 6. It boots the phone to the lock screen at 3.5v. The iPhone 6s will turn on but not boot at 3.2v. Most phones that have a battery with a nominal voltage of around 3.8v boot at about 3.4v to 3.5v on my power supply. Thanks for the comment though as I don't have a iPhone 6 here I can play with that with take more than 1v before it trips my power supply due to a short in the motherboard. — BurnieG
I charged the battery to 3.9 now with a charger. And it still won't turn on. Any ways to back up the whole system, since the data is the most important part. Thanks! It might be because of a short. Now the battery basically stays there. — Tuohang Zeng