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Repair information and guides for the Apple iPhone 5s that was announced on September 10, 2013. Model: A1533, A1453, A1457, A1528, A1530, A1518

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need help from someone with advanced board knowledge

so i have a 5s that came to be because it wasnt charging. after opening it i found it to have water damage. did some probing and came to the conclusion tristar needed to be replaced. after that its pulling arounds .5 amps through the charger and battery voltage is rising..however now i cant get the phone to boot past apple logo even with power from dc psu. i compared pp_batt and vcc_main to a known good board everything looks good there. then i moved to fpc connector and in diode mode i checked the voltage drop on every pin seems good. then i connected a screen and while it was powering up i tested to make sure the 5.7v was present as well as the 1.8v data line. both are there and functional. also when i try to boot it with dc power it draws 130ma, apple logo shows a 3ish seconds and then goes black. but it continues to draw the 130ma even when the screen goes dark. already tried to dfu restore and i know my tristar replacement is good, i do them all the time and can confirm the phone is now charging. what can i check now? any ideas would be appreciated. main place i found corrosion was at the top of board between front camera fpc and digitizer fpc. also at the bottom of the board near the battery connector and charge port. also it was ultrasonic cleaned a few times with a crest ultrasonic cleaner and branson ec

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no can ever help me with my issues on here, i always end up answering my own question after a few days....is this one any different? probably not but cant hurt to try.

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Just to confirm, because you don't mention it specifically, did you remove the shields before putting it in the bath? You said you tested the fpc in diode mode...which one ?

It sounds like it was kinda working before you got it, minus the charging issue but now it is boot looping. I would take a step back and start probing the outputs of the PMIC to see if anything is shorted. Then power up the board again and test the output voltages of the PMIC. If something is amiss, it could help you identify the problem. Boot looping means a subsystem is failing during the boot process. The PMIC powers all of the critical digital subsystems. You could also check PMU_RF, which does the same for the RF subsystems.

Probe and report back.

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yes i removed the shields before cleaning, and the fpc i probed was the lcd fpc.

and no it was bootlooping when i got it, 1st thing i did was check for short on vcc main and vcc batt then hooked up the dc power so see what it was doing. and it was bootlooping from the start. pmic was the next thing to check on my list, but i didnt wanna just remove it because i know how hard it is to replace seeing how the processor is almost directly on the other side of the board. i checked the caps in diode mode that are connected to the pmic and none seem to be out of spec tested against known good board. i guess now i gotta apply power and see if the voltages are there.

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Then you should edit this part of your question: so i have a 5s that came to be because it wasnt charging. after opening it i found it to have water damage.

:>)

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im good about not overheating the board dont worry, i dont think i caused any damage from removing the shields or replacing tristar or i would see solder balls oozing out from underfilled chips. also ive been doing logic board work for about a year and have fixed many water damaged phones, its just alot harder to diagnose when its an open line and not a dead short.

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that was just what the customer told me when they dropped it off. that it wouldnt charge

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No worries on my end, just teasing you. Don't forget to look at PMU_RF. We tend to forget it but if its isn't working properly, it can also wreak havoc on the boot cycle.

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