2019 iPad 7 Wifi A2197 does not power up

Question

iPad 7 Wi-Fi

2019년 9월 25일에 출시된 7세대 iPad는 32 또는 128GB 모델로 제공됩니다. 모델 번호 A2197.

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Ted @ted78042

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게시됨: 2023년 11월 23일

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2019 iPad 7 Wifi A2197 does not power up

Hi,

My iPad A2197 fails to power up. Since having the CPU replaced (as suggested elsewhere) would cost more than buying another iPad, I've decided to have a go at repairing this myself and hopefully up my skill set at the same time. I figure it's better than chucking it straight in the bin.

With the aid of schematics and a component placement diagram, and using my probe, I've found that caps C8120-C8126, C8180 and C812F are shorting to ground. All caps are connected to PPVDD_S1_SOC. As it's unlikely that they've all failed, I'm wondering what could be causing this short.

Any suggestions as to what to do to further narrow down the problem? What additional information would you need me to provide? TIA!

Ted

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EDIT: on further examination, it seems other caps elsewhere on the board which sit on PPVDD_S1_SOC also shorting to ground. At this point, I am starting to suspect it could be the infamous CPU connection issue although I really hope it isn't. Does anyone disagree?

Ted 의 2023년 11월 23일

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EDIT: on further examination, it seems other caps elsewhere on the board which sit on PPVDD_S1_SOC also shorting to ground. At this point, I am starting to suspect it could be the infamous CPU connection issue although I really hope it isn't. Does anyone disagree? — Ted

Alisha C @flannelist 평판: 37.9k 28 42 36 · Answer 1 · 2023-11-23T07:01:00-07:00

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Alisha C @flannelist

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There are a few things I would note in your situation.

How do you know it's short to ground? What is the actual resistance you ground you're getting? Many if the power lines that go to the CPU are naturally low resistance so this may be a normal reading.
When any component on an electrical line is bad it has an effect on the whole line. So one bad cap would cause any component on that line to read as short to ground. It's like punching a hole in a hose. Doesn't matter where else on the hose you poke, it's still going to be leaking water.

No power on these can be any number of things, but it sounds like you're on the right track.

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Thanks for the advice. I was using diode tester mode to determine the shorts. I rechecked and resistance values are around 14.7 ohms. As per my additional comment, I've since found that the other components on PPVDD_S1_SOC (there aren't that many) are also going to ground. Do you reckon it could be the CPU?

Ted 의 2023년 11월 23일

@ted78042 I happen to have an iPad 6 board at my immediate disposal that I know works, and I am also getting about 14 ohms on that line. As I said, I suspect that line is just a very low resistance line naturally. That's the case for many of the electrical lines that power the CPU (like this one).

For context.

PPVDD - Which is essentially noting a positive power supply voltage.

S1 - The power state. S1 is just below the device is fully on.

SOC - System on a Chip, the CPU.

It could be the CPU anyway, but I would probe around and see if you can find any other shorts, or anything that looks off. How did the device die?

Alisha C 의 2023년 11월 25일

@flannelist I poked around some more and the tester bleeped for quite a lot of other caps but as you say, switching to resistance readings showed that those lines had very low resistance.

I've read elsewhere that this particular iPad model is known for having CPU contact problems and that reballing was the solution. However, I most definitely do not have the skills nor the tools to attempt something like that.

I've no idea how it came to die; it just failed to turn on one day. Quality control failure, I imagine. :-/

Ted 의 2023년 11월 28일

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iPad 7 Wi-Fi

2019 iPad 7 Wifi A2197 does not power up

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