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Second repair of iPad motherboard is definitely more difficult than the first repair. In this issue, we have a case about iPad Pro 12.9 3rd not charging. We and Phonefix will learn how to perform the second repair of iPad motherboard.
When received the iPad Pro 12.9 3rd motherboard, Observed under a Soldering Microscope that the chip U3650 was missing from the iPad motherboard. Fixed the iPad motherboard with a motherboard bracket, used a Hot Air Gun to evenly blow hot air gun to melt the solder joints, and used Precision Tweezers to clamp and move the chip U3650 found on the disassembled material board to a fixed position, and soldered the chip U3650 to the iPad motherboard. Connected the voltage and current meter to the soldered motherboard for testing.
1. During the test, it was found that there was no voltage at the common point PPVCC_MAIN. This voltage was output by U8500, while the power supply PPVBUS_PROT of U8500 had no power input.
Under normal circumstances, PPVBUS_PROT is output by Q8000 or Q8001. When the iPad Data Cable is plugged in, it is Q8001 that is turned on to generate this power supply.
2. After the Voltage and Current Meter is turned on and the input end of Q8001 is measured, found that there is 5V power supply, indicating that the front-stage power supply is normal and the conduction of Q8001 is controlled by U8000. In order to rule out the problem caused by the U8000 chip, we replaced the U8000 chip, turned on the power and tested it again, and found that the common point fault still exists. Then we directly measured Q8001, and the fault was still not solved. Therefore, it is judged that the problem is not in the conduction link of Q8001, but to continue to look for the cause in its upper signal part.
3. The U8000 start signal is controlled by CD3215. When testing CD3215, the data displayed by the test instrument is abnormal, so we replaced CD3215 and checked it.
4. After replacing the iPad CD3215 Chip, the voltage and current test meter was turned on again for testing. The data showed that it was normal, indicating that the common point fault problem was on the CD3215 chip, and it was repaired after replacement.
In the case of iPad Pro 12.9 3rd not charging, the probability of CD3215 damage is relatively high. If you encounter the same fault next time, you can use the tail plug tester to test and then replace the iPad Tail Plug, because the tail plug part may also have problems causing abnormal signal transmission. If the problem still cannot be solved after replacing the tail plug, then replace CD3215. Based on this repair experience, the probability of CD3215 damage may be as high as 90%, which means that replacing it will most likely fix the fault.
In addition, the common point voltage was measured during the repair process. When the iPad motherboard is connected to a single data cable without a battery, the common point voltage is 3.6V at the beginning, and as the current increases, the voltage will become 4.3V.
Phonefix reminds everyone that it is best to use the original Apple data cable for testing in this repair. Other data cables may have different specifications, resulting in different power-on conditions, which will affect the measurement results and repair judgments.
This is the end of the sharing of iPad Pro 12.9 3rd generation not charging fault cases. Phonefix will share more iPhone and iPad repair cases with you, and recommend more high-quality iPhone Accessories and iPhone Repair Tools. To learn more about iPhone repair knowledge and cases, please visit China Phonefix Website and exchange repair experience with us.
