Multiple shortages on board (~0.1mA)
I’m trying to repair my iPad 6th and as far as I’ve tested it drains ~0,44mA with battery and ~0,11mA without. Nothing outputs on screen, but connecting to PC ends with a message in iTunes with damaged software, but iTunes couldn’t recognize the device.
On the board itself there is nothing unusual for optical review, but there are a lot of shorts, as shown on the picture.
In PhoneBoard app you can find this iPad on Air2019 position, and the nets, that are shorted to ground are: 5, 11, 23, 29, 46.My question is - since shorts are all over CPU, but it still tries to communicate with PC - is there any chance to repair it? On my own, I could try to reflow PMU or CPU, or give it to replacement to a befriended technician, but still - is it worth any tries, and if yes then what should I aim for?
what measurement you see when testing those connections? Are you sure that is a short circuit?
由 bert.harmidomski 完成的
Yep, a dead short - it's about 3Ohms so just cable resistance, and diode check drop is close to 0.
由 MakerBuddy 完成的
@MakerBuddy I am not convinced that is actually a short. If those are CPU lines (I am not at home so i can't pull up ZXW to check) a very low resistance to ground is actually normal. Many of those lines are extremely low voltage to start, so there isn't a lot of wiggle room for added resistance.
Also. I would avoid a CPU reflow. 99.9% of the time. CPU is underfilled and trying to reflow is going to do more damage than good.
When you say it drains ~.11mA without battery, that's before you try to boot or after? Is it a steady reading?
由 Alisha C 完成的
@flannelist the line looks like power supply, so I expect to see low resistance, but it's quite spread around, and between shielding-GND and shielding-power side there is the same resistance.
I really do not count on reflow since it's good for internal chip damage repair rather than cracked solder balls repair, but it is only what I can do on my own since I do not have equipment and skills to lift CPU.
Yes, ~0.11mA is as steady as my cheap USB meter can show. Basically nothing happens when I try to boot, and the device only reacts on hard reboot (power, vol-, home or smth).
An update, which I can give, is that after freezing the chip surface (I know it's not the best approach, but I do not have access to thermal camera) the first thing that evaporates is the corner of A10 chip (upper right corner on the image), so I'm afraid that CPU could be dead, or shorted underneath.
由 MakerBuddy 完成的
@MakerBuddy I agree, does look like likes coming from the PMU. But I pulled up phoneboard (Just FYI if this is an iPad 6, I believe it is SLIGHTLY different from the 2019 iPad which is iPad 7) and the lines you are getting low resistance on go to the CPU which would tell me. power for the CPU= low resistance is normal.
This doesn't sound like a short to me. If it's drawing power from USB, plugging the USB cable in will prompt the device to boot. So this is after boot prompt. .11 A doesn't seem like a short to me.
You said iTunes says it has damaged software, probably this is booting to DFU. But you say it won't restore/update? Is there some sort of error message you get?
由 Alisha C 完成的