Iphone 5s - after replacing Tristar got stuck on Apple Logo

[Alber_the_Learner]

Is that common to happen to an iPhone 5s? Replacing the Tristar and get stuck in Apple Logo?

About 6 months ago I got a 5s donor board (the whole phone) with charging problems. It was working fine on DCPS or with a fully charged battery, but it was not charging.

I changed the Tristar and then, I got stuck in the white apple after prompt to boot. I can't remember what current consuption I got in DCPS. At that time, for some reason, I took the PM8018 off thinking that was the problem -- I can't remember why, but It seems I found out a missing voltage on the PM8018 and I thought the BB_CPU was the problem.

I left it behind without resoldering the PM8018, because my BGA soldering skills was not good enough at that time and I did not have new PM8018 chips.

I want to grab that board to work back on it and troubleshooting.

1) Since I don't a new chip, I will take one off from a donor board that works, will reball the PM8018 and put it back on the board.
2) Then, if the phone boots and get stuck into the white apple logo again, I will restore it.

That will be my learnig experiment!

Any other advice?

[Jessa_the_Professa]

I would change that tristar again before doing any of that. You had a recent tristar earlier that had bridged lines under it--most likely case here if you have a phone that boots, you change tristar, and now phone doesnt boot = your tristar job is bad. This is especially true if you were recently bridging balls under tristar and this job is from long before that.

[Alber_the_Learner]

Yeah, your advice really does make sense! At that moment, my soldering skills were not good as it is nowadays. I was learning...

And also, I just remember that I don't need the BB_PMU for booting the phone!

[Alber_the_Learner]

Considering the Tristar was really bad (I am very sure about that! No charging, tried with good known parts - new battery and new USB docking port - and still not charging) and assuming that I made a mistake by assuming the PM8018 was bad, when it wasn't, my conclusion is this:

After the Tristar replacement, I got a software corruption as a secondary issue. The problem would be solved just by a simple update and if that doesn't work then a complete software restore.

Am I right in my conclusion?

[Alber_the_Learner]

I posted this one before reading Jessa's post #2...

[Alber_the_Learner]

Question just for learning purposes...

What should be the current fluctuation on DCPS that "seems to be booting, but it doesn't" and suggests me a sofware secondary corruption?

In my guessing, any of these:

1) when it reaches up 1A and than goes to zero (like this 0A, 0,25, 0.5, 0.9, zero, and again and again...)
2) when get stuck on Apple logo with a steady current consuption

Any other synthoms?

[Jessa_the_Professa]

you could try to restore first, but i would change tristar and then try to restore. You wouldn't want to risk corrupting the NAND if there are bridged lines. The other possibility is too much heat at tristar causing overheating/bridging at baseband cpu on the opposite side. A phone that boots that needs a straight up tristar replacement doesn't really get software corruption unless something happened during tristar change. Software corruption is very common with tristar failures, but usually that is in a phone that is 'living with' a bad tristar for a long time and ultimately gets data corruption.