IPad Air not charging 4.05v on USB line

[deegee2016]

Hi all,

I had a request to replace charging flex which I did , all sweet as a but but I'm only getting 4.05v on what should be 5v line , I'm pretty sure there is something shorting pulling the 1 volt down . TRISTAR???

any ideas would be welcome, I'm getting 4.05v around TriStar also and at the switching MOSFET....


Thanks in advance

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[mcmihai003]

Originally Posted by deegee2016

Hi all,

I had a request to replace charging flex which I did , all sweet as a but but I'm only getting 4.05v on what should be 5v line , I'm pretty sure there is something shorting pulling the 1 volt down . TRISTAR???

any ideas would be welcome, I'm getting 4.05v around TriStar also and at the switching MOSFET....


Thanks in advance

Sent from my X98 Plus 3G using Tapatalk

Hi,
Did you find what is causing that?
I'm having the same issue on mini2: usb line ~3.8V; if remove mosfet (q8123) line came back to normal...
Tablet not charging and not sensing USB; if started by power on button start normally
Found that if i supply 4.8V from PSU to USB power line is start...
Also, once started by power button, the USB rail come back to normal and tablet is detected normally by iTunes.
Thx!

[deegee2016]

Originally Posted by mcmihai003

Hi,
Did you find what is causing that?
I'm having the same issue on mini2: usb line ~3.8V; if remove mosfet (q8123) line came back to normal...
Tablet not charging and not sensing USB; if started by power on button start normally
Found that if i supply 4.8V from PSU to USB power line is start...
Also, once started by power button, the USB rail come back to normal and tablet is detected normally by iTunes.
Thx!

Hi there,

I still have the device and was going to go back to it as my thinking was same as you . I think an ic is pulling the voltage down as there I'm getting no reading at all in diode mode on that line and the only thing connected is the Q8123 MOSFET . So my thinking is to first remove the inductor L6157 to split the line and see if I get 5v at the flex side of the line via feed pad , had a similar issue with an iPhone where the was no reading at all on the 5VO_USB line and after I jumped the MOSFET and had the line back.

Thanks for your input , it has spurred me on to go back to the device and try the above .

Seemed as though once the Q8123 is replaced or jumped to test all should be OK .

Please keep me updated on your repair as I will mine

Regards Dee

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[mcmihai003]

Originally Posted by deegee2016

Hi there,

I still have the device and was going to go back to it as my thinking was same as you . I think an ic is pulling the voltage down as there I'm getting no reading at all in diode mode on that line and the only thing connected is the Q8123 MOSFET . So my thinking is to first remove the inductor L6157 to split the line and see if I get 5v at the flex side of the line via feed pad , had a similar issue with an iPhone where the was no reading at all on the 5VO_USB line and after I jumped the MOSFET and had the line back.

Thanks for your input , it has spurred me on to go back to the device and try the above .

Seemed as though once the Q8123 is replaced or jumped to test all should be OK .

Please keep me updated on your repair as I will mine

Regards Dee

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Already tried replacing Q8123, and get the same 3.8V when connected to USB.
What is curious is that i get ~100K between rail and GND, and if i feed the line with 4.8V from PSU the voltage on rail is OK (~4.8V) and board start to boot..

[iphonerepair12]

Did you try to change U6000 ?

[deegee2016]

Originally Posted by iphonerepair12

Did you try to change U6000 ?

Well , I have 4.03v at Q8123 PINS 8,7,6,5

I have no voltage at C8245

I have no voltage at TriStar :

PP3V0_S2R_TRISTAR = 0V

PP1V8_S2R_TRISTAR = 0V

PPVBUS_PROT = 4.03V

I'm thinking TriStar is the problem here any ideas?


I get diode readings of 500mv + on the outgoing side of Q8123 but nothing on the incoming side unless a charge cable is plugged in .

Kind regards Dee

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[mcmihai003]

Originally Posted by deegee2016

Well , I have 4.03v at Q8123 PINS 8,7,6,5

I have no voltage at C8245

I have no voltage at TriStar :

PP3V0_S2R_TRISTAR = 0V

PP1V8_S2R_TRISTAR = 0V

PPVBUS_PROT = 4.03V

I'm thinking TriStar is the problem here any ideas?


I get diode readings of 500mv + on the outgoing side of Q8123 but nothing on the incoming side unless a charge cable is plugged in .

Kind regards Dee

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Just a thought: what if usb lightning connector don t provide 4.7V due to whatever reasons?
Because in my case if i inject 4.7V directly to Q8123 tablet start normally

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[deegee2016]

Originally Posted by mcmihai003

Just a thought: what if usb lightning connector don t provide 4.7V due to whatever reasons?
Because in my case if i inject 4.7V directly to Q8123 tablet start normally

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I think its due to the fact of the MOSFET is always below 5v to enable it to detect high voltage allowing it to start to charge. Battery voltage is low and when charger is plugged in it goes higher than battery voltage and switches to the TriStar pin to enable to charge . I maybe wrong but that's how it works on I phones....

I've just had some 1610a1 delivered so will try tonight and keep u updated..

Kind regards Dee

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[deegee2016]

Originally Posted by mcmihai003

Just a thought: what if usb lightning connector don t provide 4.7V due to whatever reasons?
Because in my case if i inject 4.7V directly to Q8123 tablet start normally

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4.7v is higher than bat voltage so it should switch over ...

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[deegee2016]

Originally Posted by deegee2016

4.7v is higher than bat voltage so it should switch over ...

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Update: Like I stated before my USB line to the inductor was 4v instead of 5v once I replaced the dock flex , I had to manually boost charge the battery as it was at 0.00v stone dead.

Plugged it in still nothing on my dcps by way of load. 5v (USB) set to 2a but still 0.08a

I then decided to replace TriStar after removing the most pain in the *** solder mask that was already applied to the IC.

Once TriStar was removed I had the 5v back fully.

TriStar was replaced and at first plugged into laptop was chiming, but charging at 0.40a

Then plugged in the LCD and then used a 2amp wall charger and the amp draw was now over 1amp and charging , and signals to usb were checked for functions,:

Remove charger shows charger needed icon

Plugged back in showed battery icon

After charging over night fully charged at 100%.

SOLVED!!!!!!

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[giorgioz12]

same problem, I removed u6000 but I have not fixed, I changed the charging connector but I have not solved, tried to replace q8123 and q8104 but I have not fixed, the ipad off when I connect the cable turns on, it comes to the screen but at the top does not display charging, then stops absorbing amp, passes from 1.68 to 0.00A
Help me...

[deegee2016]

Hi, If the device turns off when charger plugged in , I would imagine there's a short.

Edit: forget the short misread, carry on with tests but check battery and TriStar install by voltages.....

I would test from port to solder pads on board,, confirm continuity, bridged pads short to ground and then the 5volt supply feed to the solder pads on the flex . local test point is fine.

If you have 5v then move on.

If the logic board is back in housing use the inline inductor by the FPC sockets that's the first or second component on that line . 5v move on

Then I check for voltage at the cap near the mosfet Qxxxxx can't remember the name should show 5v one side . 5v move on

Refer to the rest of test in my post for TriStar voltages , it seems TriStar may be bad install with respect,

Seems like short and possibly bad TriStar pads its a USB controller and has USB data lines.


Hope it helps.

Also make sure battery has at least 2.8v I think it needs for the charging process to proceed

Regards Dee



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[deegee2016]

For future reverence anyone carrying out installation on ICS or components must always test the install prior to energising . one for peice of mind secure connections and two to prevent short damage ..

Regards Dee

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