ipad air 9th gen a2602 not powering up after charging port replacement

[kjchatman]

i'm new to fixing ipads. i've replaced a few ports but i've not done any other troubleshooting so i'm trying learn more. What voltage should read on the battery terminal if the battery isn't connected but the charging cable is connected? i'm getting a reading but it's not stable

[mon2]

Hi.

1) Highly recommend the 'Qianli Tail Tester' tool which can be used to quickly confirm the USB-C and lightning ports on these devices.

https://www.aliexpress.com/item/1005001463633327.html

https://www.mobilesentrix.com/ibridg...-tester-qianli
* cheaper to buy through Mobile Sentrix

2) The suspect for your case is the replacement charging port. In the absence of the above tool, you can test each soldered pad on the flex pcb in DIODE mode. Remove all power. Meter in diode mode. Red meter probe, yes RED to ground. Black meter probe to the point to measure. The above tool does the same but in a few seconds and to us, is priceless.

The concern is if each such pad is truly mating with the PCB pads to complete the connection. Respectively, you may not even have power going onto the logic board. Approach with caution as the parts are very very small. Not our favourite repair jobs but we do a few here and there.

[kjchatman]

i'm sure that i put the charging flex cable on with accuracy. what should the voltage be on the battery terminal with out a battery attached?

[mon2]

What is the voltage you are observing at the battery connector (without the battery)?

What is the current draw of this logic board with your power supply? Is the power supply cycling? Do you have a thermal camera?

[kjchatman]

3.8v on the battery terminal. it' barely drawing any current at all. .060 amps

[kjchatman]

a lot of the pins that connect to the charging flex cable aren't connected. they read as OL in diode mode to ground. would that be a charging IC issue?

[mon2]

Yes. As mentioned in post #2.

[kjchatman]

1614a1 ic?

[mon2]

No. Based on my experience, the small pads on the flex cable do not mate with the logic board after alignment. Suggest to flux this entire flux pcb and then touch each pad to force the solder to melt and create a fresh joint.

There is a really good video from Alex on this - let me see if I can find and link it here. Suspecting this replaced flex cable as the root cause unless proven otherwise.

The 'tail' tester from Qianli is gold here for verification of the replaced cable.

Alex's video (also voice of the Aardvark cartoon):

https://www.youtube.com/watch?v=qeT-FdvYyxg


(tests both USB-C and Lightning)

[kjchatman]

but i removed the flex cable to be sure and those pads are still reading OL in diode mode

[mon2]

I will suggest to review the schematic and boardview files of other ipad models with similar charging cables. Such documentation will offer diode mode readings for the charging port. Use the values to gauge the status of your case. It may very well lead down to need to replace the tristar part on your ipad. There are many variations of this tristar part and they appear to be available at least on Aliexpress. You can also check Mobile Sentrix (VA for you; Toronto for Canadians). Mobile is often at the same or even lower than Aliexpress pricing for many parts. OL usually means that the line is floating / is open circuit.

To confirm, you have read meter lead to a known good ground contact; black meter lead to the point to test.

Always triple check. I personally serviced a macbook A1932 which I will document in another thread. 2 local stores said it cannot be fixed and the motherboard was defective. Almost ran into the same conclusion from the client's feedback but after a bit of debugging, the macbook is working and the root cause was a shorted cap on a remote audio board. Needle in a haystack. Respectively, even though this ipad is not well documented, engineers like to borrow from proven designs so we too can learn from other ipad models.

[kjchatman]

i ordered that Qianli Tail Tester for the future but i don't think this one has a problem with charging now that i've replace the charging flex cable again. It still doesn't power up but it's probably a pmic issue since the power button doesn't have 3v

[mon2]

The current draw will be very helpful. Would you have a thermal camera? If yes, hunt for any shorted parts.

[kjchatman]

i have a thermal camera that i use all the time to do repairs but this board isn't drawing any current

[mon2]

So stuck @ 5v 0A current draw?

[kjchatman]

yes

[mon2]

Perhaps should have done this sooner but from a quick Google search, found the following compatibility list. The same cable is also used on ipad7; ipad8 as well as your ipad9.

Proceed to study the pinout for this charge cable using the available schematics from ipad7 or ipad8. Locate the VBUS pin(s) from the charger to the logic board. Also locate the ground.

Then remove all power / no battery. Meter in diode mode. Touch your meter probes together and should have a tone beep.

Touch one probe onto the ground of the flex cable you have soldered (at the PCB pads) and other probe to metal shield on the board. You must hear a tone beep.

Next, red meter probe, yes red to metal shield. Black meter probe onto the vbus pad(s). You must have a valid measurement here - not 'OL'. If you see 'OL' - the pad on your charging port cable is NOT soldered to mate to the bottom ipad port pad. Been there, done that and killed far too much time (the first time doing the same repair). Flux the crap out of it (50% of what Louis shows in his videos) + heat that pad up good.

Repeat to test in DIODE mode using the same method till you have a valid reading for each pad that is connected to something on the board. If 'OL' = the pad is floating.