Hello,
I bought an iPad 4 from eBay which is not powering on and wanted to troubleshoot the problem just for fun.
But the fun ended when I stuck... I don't know what to do next and I'll be thankful for a bit of help.
What I know so far:
Pluging the iPad to the charger charging the battery with around 2.3-2.4A, which is OK IMO.
Pressing the power button does nothing. Press and hold the power button + home button (to reset the device) does nothing (it is resetting but still doesn't turn on).
I dissassembled the tablet and made some measurements to see which power rail is missing and it seems like PP3V0_GRAPE and PP3V3_ACC are missing. Didn't detect short on any of these power rails and I'm not sure if any of these are critical for the tablet to boot.
What else I did is to connect the motherboard direectly to the bench power supply to monitor the current. When I connect it - 0A. Short press the power button 0.070A for a while. Long press the power button(start up) - going to 0.120A for 1 sec and then constant 0.087. And that's it, it is staying like that and nothing more can be done without reattaching the power.
Any suggestions how to proceed, what is ought to be failing, tristar chip with missing PP3V3_ACC or grape chip with missing PP3V0_GRAPE? Is some of these rails vital for the tablet to boot up?
I am attaching the measurements I made while troubleshooting the problem.
Side question:
Is there any pattern to recognize which rails should be present when the tablet is On, Off, Standby? I know there is convention for MacBook to have postfix such as S0, S3, S5 in power rail list in the shematic, but in my version of the schematic there are no postfixes...
Thanks!
I bought an iPad 4 from eBay which is not powering on and wanted to troubleshoot the problem just for fun.
But the fun ended when I stuck... I don't know what to do next and I'll be thankful for a bit of help.
What I know so far:
Pluging the iPad to the charger charging the battery with around 2.3-2.4A, which is OK IMO.
Pressing the power button does nothing. Press and hold the power button + home button (to reset the device) does nothing (it is resetting but still doesn't turn on).
I dissassembled the tablet and made some measurements to see which power rail is missing and it seems like PP3V0_GRAPE and PP3V3_ACC are missing. Didn't detect short on any of these power rails and I'm not sure if any of these are critical for the tablet to boot.
What else I did is to connect the motherboard direectly to the bench power supply to monitor the current. When I connect it - 0A. Short press the power button 0.070A for a while. Long press the power button(start up) - going to 0.120A for 1 sec and then constant 0.087. And that's it, it is staying like that and nothing more can be done without reattaching the power.
Any suggestions how to proceed, what is ought to be failing, tristar chip with missing PP3V3_ACC or grape chip with missing PP3V0_GRAPE? Is some of these rails vital for the tablet to boot up?
I am attaching the measurements I made while troubleshooting the problem.
Side question:
Is there any pattern to recognize which rails should be present when the tablet is On, Off, Standby? I know there is convention for MacBook to have postfix such as S0, S3, S5 in power rail list in the shematic, but in my version of the schematic there are no postfixes...
Thanks!
Attached Files