iPad 5th gen (A1823) - No charge but recognized by finder

[Carl0s-]

Hi,

Sooo - our IT got a pile of old iPads that the sales guys have been mistreating. These are free for grabs if you want to try to get one working. Thought I'd give it a try - if I get at least some life to I can give to my kid to entertain during a car rides.

But the iPad it self - its a 5th gen cellular model. When I initially plug it in it was completely dead. It was not recognized by my Mac nor it started to charge. Disassembled it opened up the battery connector and checked the battery voltage. My multimeter showed 0,7v. Had a spare micro-usb charging board lying around, so hooked it up on my probes and gave the battery some startup juice. Kept the power on for ~15minutes and the after disconnecting the battery voltage was 3,6v.

Reconnected the battery connector to the motherboard and connected the device to my Mac and behold! it started right up and after a while, my Mac recognized it and it were visible in finder - But I immediately noticed that it was not charging. Data connection works fine, but its just not charging...

Any ideas if its common issue? Or where should I look next?

[mon2]

Remove all power. Meter in resistance mode. Check the resistance to ground of the battery + connector on the logic board. No battery should be connected / no power cable should be connected during these tests.

What is the resistance (not diode mode) measurement?

[Carl0s-]

Remove all power. Meter in resistance mode. Check the resistance to ground of the battery + connector on the logic board. No battery should be connected / no power cable should be connected during these tests.

What is the resistance (not diode mode) measurement?

Measured from the logic boards + terminal to the chassy of the iPad I get no connection at all. Measuring from the negative battery terminal of the logic board to chassy I get 0,1ohms

[mon2]

Is your meter an autoranging type or do you manually select the resistance scale? If manual scale, shift to a higher scale till you have a resistance reading for the '+' to ground.

[Carl0s-]

Is your meter an autoranging type or do you manually select the resistance scale? If manual scale, shift to a higher scale till you have a resistance reading for the '+' to ground.

Hi,

Its auto ranging - momentary I were able to get reading of 17 Mohms but it went away. Almost like connector would be bad and having intermittent connection - but after measuring reconnecting the battery made it power right up.

[reformatt]

Most common issues on iPads are bad charging connector or bad Tristar IC. Bad batteries (or no battery sense comms) usually result in boot loops. Use 3uTools to see if you get any battery sense data at all.

[Carl0s-]

Most common issues on iPads are bad charging connector or bad Tristar IC. Bad batteries (or no battery sense comms) usually result in boot loops. Use 3uTools to see if you get any battery sense data at all.

3uTools seems to be able to pull battery data just fine... What caught my eye is that its only been trough 32 charge cycles :/ ... Soo, the Tristar IC is the next suspect?

[Carl0s-]

Did some measures using multimeter:

when the logic board is connected to a power bank and I measure from where the flex cable connects to the logic board I get 4.8v (which goes away when I pull the plug). While the logic board is connected to the power bank, if I measure the logic boards battery terminal I get 0,4v so I guess its the actual "power electronics" that have gone bad

I was thinking: I have spare micro usb powerboard that could fit in place of the original lighting port after some modifications. Threat or possibility if I pull jumper wires from that micro usb charge board to the logic boards battery terminals and use that to charge the battery? Yeah, I would need to snap off the lightning connector to get some room but I can live with that.

[mon2]

Suggest to not take this approach. Remove all power. Meter in DIODE mode. Connect the RED meter probe to ground (yes RED); black meter probe to L8512. Test both sides of this coil.

Do the same for PPBATT_VCC (pin # 5 of Q8504).

Post each measurement.

[Carl0s-]

Suggest to not take this approach. Remove all power. Meter in DIODE mode. Connect the RED meter probe to ground (yes RED); black meter probe to L8512. Test both sides of this coil.

Do the same for PPBATT_VCC (pin # 5 of Q8504).

Post each measurement.

Hi, atm i don't have schematics - found some iPad 5 schematics from this forum but non of the test points / components line up. After I find proper schemas I will do above measurements and post results 👍

[mon2]

For A1823??

[Carl0s-]

For A1823??

Yeap

[Carl0s-]

Suggest to not take this approach. Remove all power. Meter in DIODE mode. Connect the RED meter probe to ground (yes RED); black meter probe to L8512. Test both sides of this coil.

Do the same for PPBATT_VCC (pin # 5 of Q8504).

Post each measurement.

Here's the measurements:

L8512-1: 0,142v
L8512-2: 0,141v
Q8504-5: 0,667v

[mon2]

Diode mode reading of the inductor looks low. Remove all power and test the same inductor in resistor mode. Post the resistance to ground.

[Carl0s-]

Hi,

L8512-1to GND ~1Kohm
L8512-2 to GND ~1Kohm

[mon2]

No issue here. With your meter in DC volts scale (10 volts or higher is ok); measure the voltage to ground of PPBATT_VCC. You can probably do this by probing (carefully) C8576 (pin #1).

See attached. Red probe here and black probe to a ground (shield is ok). Do this after you connect the external USB power adapter to this logic board. If all is well, you should have a charge voltage here to charge the battery.

[Carl0s-]

I get no voltage on Q8504-5 nor I get any voltage in Q8504-"123". If (big if) I intreper the schemas correct in 123 there is the PPVCC_MAIN ( tho can't figure out where this one is being fed ) which the Q8504 somehow regulates to charge the battery via Q8504-5 (PPBAT_VCC). Currently the logic board is out of the chassy (so no battery connected) and run by external USB power. Should I repeat the previous voltage test with the battery connected?