ipad 4 no power - GSM-Forum

willipad · 09-14-2018, 10:02

hi i'm willi,

i am trying to repair my ipad 4 wifi for a while. it doesnt power on now. before this complete breakdown the ipad randomly rebooted. i have tested several voltages and other values around vcc_main on the board.

PPVBUS_PROT 5V
PPVCC_MAIN 2.3 - 2.5 V alternating
ACT_DIO 0.2 V
D8100 Reverse Voltage 0.152V
PPVCC_MAIN to GND 1.345kOhm

sadly all capacitors look create either.
i really need some expertise from your community.
has anybody an idea, what i can do next?

thanks

orx · 09-14-2018, 18:41

hi

do you've tried with usb cable connect to usb test meter for absorption ?
do you've tried to connect power supply directy to the m.board for to check shorts ?
do you've tried to go in dfu and to check it is recognized from pc ?

ipad 4.JPG

willipad · 09-14-2018, 19:37

hi, thanks for your help.

Unfortunately I don't own a usb test meter, but i already connected power supply to VCC_MAIN to check for shorts.
Sadly there is no heating at any component at the board.
I also tried to go in the dfu mode, but either the computer or the ipad react in any way.

Further i noticed a switching noise, when the usb cable is plugged at the lightning connector.
I saw the picture you sent, do you recommend to unsolder the two capacitors? what do you mean with checking the jumper?

Thank you very much, i am willing to unsolder every component to get this stuff work again

orx · 09-14-2018, 20:03

the 2 capacitors are for to stabilize the charge
they can create a disturbance to the line , what do you mean with checking the jumper? it's a filter, check with tester / multimeter if has continuty , if no desolder and jumper.
another possibility from noise could be charging line so replace dock ( can to be in short) and in sequence ,carefully replace usb charging ic (u2) 1608A1.

usb meter I warmly recommend it costs little and helps a lot

willipad · 09-15-2018, 11:51

thanks for your assessment.

Shortly before i started to unsolder the capacitors, i gave the board a last try.
Surprisingly the behavior changed, now i get

PPVBUS_PROT 4.8V
PPVCC_MAIN 3.46 V stable
VDDQ=VDDCA 1.93 V
VDD2 1.01 V
VDD1 1.79 V

and the A6X Chip is hot
and the PMU (U8100) is very very hot

the iPad is still unresponsive at the display and the pc
the switching noise is gone by the way

do you think i should still unsolder the capacitors?

i will have a look at such usb meter, now i can say, that the power supply heats up a little bit

orx · 09-15-2018, 15:56

no problem bro

at this point before to think to replace U8100 pmic try to replace U2.

good luck

willipad · 09-16-2018, 09:06

Ok thanks, i'll try it

09-14-2018, 10:02	#1 (permalink)
willipad Junior Member Join Date: Sep 2018 Posts: 4 Member: 2865158 Status: Offline Thanks Meter: 1	ipad 4 no power hi i'm willi, i am trying to repair my ipad 4 wifi for a while. it doesnt power on now. before this complete breakdown the ipad randomly rebooted. i have tested several voltages and other values around vcc_main on the board. PPVBUS_PROT 5V PPVCC_MAIN 2.3 - 2.5 V alternating ACT_DIO 0.2 V D8100 Reverse Voltage 0.152V PPVCC_MAIN to GND 1.345kOhm sadly all capacitors look create either. i really need some expertise from your community. has anybody an idea, what i can do next? thanks Last edited by willipad; 09-14-2018 at 10:12.

09-14-2018, 18:41	#2 (permalink)
orx No Life Poster Join Date: Oct 2012 Location: Republic of Serenissima Posts: 1,516 Member: 1825965 Status: Offline Thanks Meter: 874	hi do you've tried with usb cable connect to usb test meter for absorption ? do you've tried to connect power supply directy to the m.board for to check shorts ? do you've tried to go in dfu and to check it is recognized from pc ? ipad 4.JPG

09-14-2018, 19:37	#3 (permalink)
willipad Junior Member Join Date: Sep 2018 Posts: 4 Member: 2865158 Status: Offline Thanks Meter: 1	hi, thanks for your help. Unfortunately I don't own a usb test meter, but i already connected power supply to VCC_MAIN to check for shorts. Sadly there is no heating at any component at the board. I also tried to go in the dfu mode, but either the computer or the ipad react in any way. Further i noticed a switching noise, when the usb cable is plugged at the lightning connector. I saw the picture you sent, do you recommend to unsolder the two capacitors? what do you mean with checking the jumper? Thank you very much, i am willing to unsolder every component to get this stuff work again

09-14-2018, 20:03	#4 (permalink)
orx No Life Poster Join Date: Oct 2012 Location: Republic of Serenissima Posts: 1,516 Member: 1825965 Status: Offline Thanks Meter: 874	the 2 capacitors are for to stabilize the charge they can create a disturbance to the line , what do you mean with checking the jumper? it's a filter, check with tester / multimeter if has continuty , if no desolder and jumper. another possibility from noise could be charging line so replace dock ( can to be in short) and in sequence ,carefully replace usb charging ic (u2) 1608A1. usb meter I warmly recommend it costs little and helps a lot

09-15-2018, 11:51	#5 (permalink)
willipad Junior Member Join Date: Sep 2018 Posts: 4 Member: 2865158 Status: Offline Thanks Meter: 1	thanks for your assessment. Shortly before i started to unsolder the capacitors, i gave the board a last try. Surprisingly the behavior changed, now i get PPVBUS_PROT 4.8V PPVCC_MAIN 3.46 V stable VDDQ=VDDCA 1.93 V VDD2 1.01 V VDD1 1.79 V and the A6X Chip is hot and the PMU (U8100) is very very hot the iPad is still unresponsive at the display and the pc the switching noise is gone by the way do you think i should still unsolder the capacitors? i will have a look at such usb meter, now i can say, that the power supply heats up a little bit

09-15-2018, 15:56	#6 (permalink)
orx No Life Poster Join Date: Oct 2012 Location: Republic of Serenissima Posts: 1,516 Member: 1825965 Status: Offline Thanks Meter: 874	no problem bro at this point before to think to replace U8100 pmic try to replace U2. good luck

09-16-2018, 09:06	#7 (permalink)
willipad Junior Member Join Date: Sep 2018 Posts: 4 Member: 2865158 Status: Offline Thanks Meter: 1	Ok thanks, i'll try it