iPhone 7 Booting not charging

[Oreo]

Hi everyone, nice to be here.
I was on the mobile repair on discord Jessa suggested i come and ask about it here, so here i am

I got this iPhone 7 which was dead not charging not booting after visual inspection i saw nothing abnormal.
So i changed the tristar the battery was dead so after plugging it on charge for awhile the phone was charging normally and booted, after it booted up it wouldn't charge.
I tested it with a known good battery and charging port but still same issue.
Again i changed tristar, but same issue the phones boots up but not charging.
I changed tigris and still same problem.

Now when plugged to dcps it shows 35mA. I am sure that i had 0 draw before but i could be wrong.
VDD Main is 0.326 diode

Thank you

[john]

Last charging issue I fixed was replacing Q2102. Was on a 7 plus so not sure if it’s the same number on the 7. But I was seeing similar low or no charging from the ammeter. You probably know this but if your using one of those usb ammeters it’s not accurate on a computer USB port. Not enough amperage coming out of those to see normal charging values

[crea2k]

The active diode / mosfet / Qsomething can cause this. I had a iPhone 6 in literally today with the same issue. Changed tristar / Tigris, it charged for a grand total of 12 hours, then stopped again. Tigris was shorted to ground, so changed that again, would power on but still not charge, changed the active diode and works fine now. I think it was possibly the active diode all along and replacing Tigris just gave it a bit of life for a few hours from the heat reviving it.

[Jessa_the_Professa]

Let's talk about the 35mA draw--that can be significant and it indicates that you have a leak to ground somewhere before the PMIC. The first step is to ask "is this kind of leak normal for your DCPS?" Have you seen this kind of leak before? If not, then we definitely want to find the cause of that before anything else. What was your vddmain diode mode reading before changing tristar? Let's check diode mode compared to known good on tigris area caps that could be partial short and tigris killers and speaker amp vboost since that is a branch of main as well.

Also, it is very unusual for an iPhone 7 to be dead due to tristar failure, that's not how they typically fail. Are we sure that this phone was a bona fide "no boot" phone from the beginning or could it have just been a not charging phone? If it was no boot, what was it's original DCPS boot signature.

I think the advice pointing you to the mosfet is good, we can rule that out, but we still want to put out that leak so this phone doesn't end up with rapid battery drain.

[Oreo]

john I took your advice but same issue as Jessa points out i am more concerned about the 35mA draw.

Jessa_the_Professa No this is not something normal for my DCPS, and no this is quit abnormal to what i am used to.
Yes, the phone was completely dead, when i got it, wouldn't charge or boot, after the tristar change it booted, and strange enough it would only charge when the battery was drained, it would charge it to the point where the phone booted and stop basily to 1-3% of charge.

Regarding the doid mode test to be honest i didn't measure those as before and after, i can compare it to a known good one and get back to you with the result.

Thank you everyone.

[Jessa_the_Professa]

Those symptoms sound a lot like tigris, or tigris related caps, or the mosfet. The problem is current sensing which would be part of the gas gauge or BAT_SWI (single wire interface) line. This is handled by tigris. When the draw from the screen comes up, the current draw in the entire device changes and the board is turning off charging in response. Since we know that tigris is "charger facing" and because changing tristar turned the phone from dead to alive we know that the device has had a 'charger insult' This means that changing tigris was certainly in order. We also know that main goes under tigris and that speaker amp is in the area---both are on main and easy to accidentally nudge or bridge. I would look around here for the 35mA leak. In general, if the leak appeared after tigris, I'd back up a step and take tigris off and see if the draw goes away.

[Oreo]

Jessa_the_Professa Yes, the 35mA is gone now after a new tigris (Had to wick off the old sold). but the main issue still remains not charging after booting.
I checked the line you mentioned and compared to a known good and they are all normal, although i am not sure what you meant by gas gauge.
I think i am going to pass this one i have already spend too much time on this phone and i am losing the motivation to continue, thank you very much for your help.

[Jessa_the_Professa]

At least jump the mosfets before quitting to test. There are many times when folks spend way too much time on a repair and should pitch it, I regularly advise people to abandon boards---this is not one of them.
This is the exact kind of repair that progresses your knowledge. It is time for you to look at the schematics and see what you can figure out for how charging really works. Find the batt_swi line. That is gas gauge. It contains all of the battery data--temperature, cycle count, battery percentage, etc. This line sounds like it would be really important to your problem "state specific charging" Find out where it goes and what the likely failure points are----it will lead you to tigris (not tristar). Let's assume that your brand new not reballed tigris rules out a tigris fault.

So what next, what do we know about state-specific charging in other devices, is it a signature problem anywhere else? Yes--in the 5c. In the 5c there is a mosfet that controls the flow of 5vusb charging current from the charge port to the charging system. We know from experimentation in the 5c that looking at the schematic and making a plan to hard wire across the mosfet--i.e. lay a wire connecting source and drain and ignoring the reverse voltage protection pad---will solve state-specific charging in the 5c and the device will consume normal charging current in all states. There is a similar mosfet in the 6--follow the path of 5vusb current from the charge port to find it.

There is a second mosfet---the one that three different folks here on this very post are telling you "hey in my experience I solved this same problem by replacing" It is a mosfet that controls the flow of battery voltage to main voltage, and the gate of the mosfet is governed by tigris on a line called active diode. Similar to the 5c experiments, you can just lay a wire across to do a test to see if hard wiring batt vcc to vccmain solves your state specific charging problem.

In my opinion it would be a shame to abandon this project without ruling out these two potential causes of the problem. It only takes some study of the schematic to figure out what and where these chips are, a little hot air and some wire.

[eDigitCom]

Not lose motivation It is great to beat a problem as least to find the cause. You learn so much from it also. These problems are the once you learn from not the once you can fix and know how to repair


This is the way I look at thinks

We have the best in Jessa_the_Professa guiding us and an excellent teacher

Thanks Jessa

[Oreo]

Jessa_the_Professa I was actually annoyed by the customer who had no patient to wait, even though i explained the process and what was up.
Personally i wanted to try and fix it, that's why i made a thread here to be guided, but i felt like the customer was ignoring and kind of headache he thought it was just another battery replacement, anyway if he comes back i can continue and update the thread.

Don't worry i have taken your advice since i started doing this, and i am still learning alot, thank you for your contribution, everything has been noted.

Thank you all