iPad 7 A2197 - no power

[martyjelen]

Hello, I have iPad that won't turn on. With connected battery there is about 450mA constant current draw. I dissasembly PCB, when I connect it without battery, there is about 20mA current draw.

No signs of liquid damage etc.

What should I check, please?

Thanks for your help.

Martin

[martyjelen]

Re: iPad 7 A2197 - no power

Same problem as described here : https://www.badcaps.net/forum/showthread.php?t=119040

[mon2]

Re: iPad 7 A2197 dead

Is the current spiking to this target current draw?

You likely have a shorted part on the battery side.

Remove all power, check the resistance to ground at the battery+ connector but without the battery connected.

What is the resistance?

Watch this video:

https://youtu.be/xqki4qHCJuw

[martyjelen]

Re: iPad 7 A2197 dead

Hello, thanks for reply. Current draw is constant all the time. Resistance on battery connector + to ground is 4 Mohm.

Already checked this video, but I think it's another case.

[mon2]

Re: iPad 7 A2197 dead

See attached. Review with caution.

Adding (Ayman who has some great videos as well):

https://www.youtube.com/watch?v=uWgPPNsdNAc

Update (again) - this video confirms there is a shorted component on the board. Remove all power. Probe all visible caps' resistance to ground. No power during these tests. Hunting for a low resistance reading.

https://www.youtube.com/watch?v=4xDV_BvcVFU

[martyjelen]

Re: iPad 7 A2197 dead

These are have very low resistance, about 12ohms.


edit: also these

[mon2]

Re: iPad 7 A2197 dead

Now locate these caps in the boardview file.

Then again in the schematic.

Then we will know to which power rail these parts are linked. Then we can determine if the low resistance is normal or not. Once at this stage, it may be worthwhile to inject a low voltage to determine who heats up.

Alex's video mentions anything in the ~400-450mA is a short... regardless of the model.

[martyjelen]

Re: iPad 7 A2197 - no power

[mon2]

Re: iPad 7 A2197 - no power

Skip this batch of parts - each is linked to a low voltage rail and respectively, is expected to be a low resistance rail.

Continue your hunt. Best to use resistance mode checks - not diode mode to locate the defective cluster of parts. That is, for example, a 100 ohm resistance will not tone beep in diode mode but yet is considered a short if it is this low of a value on a 3v3 rail.

For this reason, measure the true resistance to ground of each cap on the board.

[martyjelen]

Re: iPad 7 A2197 - no power

There are many caps under the shield which I can't reach. But every cap I measured looks OK.

[elecsoluces]

Re: iPad 7 A2197 - no power

no power : check first PPBATT_VCC and PPVDDMAIN.
Inject 4V/3A to PPBATT_VCC and try to boot the device. Report the current draw on your power supply.

[martyjelen]

Re: iPad 7 A2197 - no power

There is nothing on PPBATT_VCC. I can't find PPVDDMAIN nor PPVDD_MAIN in schematics.

Did you mean PPVCC_MAIN?

Current draw is 0A.

[elecsoluces]

Re: iPad 7 A2197 - no power

"There is nothing on PPBATT_VCC" what do you mean?
Connect your power supply to PPBAT VCC and press power button (long press) current draw is 0. Did you connect ground?
PPVCC_MAIN and PPBATT_VCC have same voltage value

[martyjelen]

Re: iPad 7 A2197 - no power

I'm sorry. Measured it wrong. There is 4V on PPBATT_VCC and also 4V on PPVCC_MAIN.

When I press power button, there is 12mA current draw.

[elecsoluces]

Re: iPad 7 A2197 - no power

"There is nothing on PPBATT_VCC" what do you mean?
Connect your power supply to PPBAT VCC and press power button (long press) current draw is 0. Did you connect ground?
PPVCC_MAIN and PPBATT_VCC have same voltage value

[martyjelen]

Re: iPad 7 A2197 - no power

Like I said. Without battery connected - It's about 12mA
With battery connected - It's about 450mA

[mon2]

Re: iPad 7 A2197 - no power

How and where are you measuring the current draw?

Are you using a dc power supply to mimic the battery?

[martyjelen]

Re: iPad 7 A2197 - no power

I have a power supply where is connected USB > lightning cable.
When I connect it this way (without battery) - current draw is 20mA
When I connect it this way (with battery) - current draw is 450mA (constant)

When I connect power supply directly to battery pin. Current draw is 12mA

[mon2]

Re: iPad 7 A2197 - no power

The boardview file will offer diode mode measurements for the charge port connector.

Suggest to remove all power and compare your readings against reference to check if the TriStar chip is ok or not. Believe that logiwki / repairwiki will also offer the diode readings of notable points on the logic board.

PS: have you tested with another known good battery?

[martyjelen]

Re: iPad 7 A2197 - no power

Unfortunately, I don't have diode mode measurments in my file. I wonder if it's the same as ipad 5 charging port. Looks similair. But I have differnet values.
https://logi.wiki/index.php/iPad_Dio...e_Measurements