Repair For MacBook Pro A1989 That Won't Turn On

ID: 139928

Description:

Steps:

1. Press the power button. The MacBook won’t turn on.
2. Plug in the BY-3200 power cable, and set the input voltage to 20V.
3. In this case the amperage is 0.047A.

4. Unplug the power cable. Next, we need to disassemble the MacBook and test.
5. Remove the 6 pentalope screws and disconnect the battery connector flex cable.

6. Plug in the BY-3200, and set the input voltage to 5V.
7. The current reading on the DC Power Supply is 0.059A.
8. In this case power supply says the motherboard is only using 5V, which is abnormal.
9. The normal power supply should read 20V. This indicates that the motherboard has malfunctioned.

10. Next we will remove the motherboard and install the power connector flex cable.

11. The motherboard number is 820-00850-07.
12. Open the schematic diagram and bitmap.
13. U3900 is the T2 chip. U7800 is the power chip.

14. Measure the standby voltage of the T2 chip, which is supplied by the U7800. Find U7800 on the schematic diagram.
15. This table shows the standby voltage of the T2 chip.

16. Plug in the power cable.
17. The motherboard's current stops at 0.06A, and the input voltage is only 5V.

18. Measure the power supply of the motherboard.
19. The measured voltage values are normal. It can be judged that the power supply circuit of the motherboard is good.
20. Next, we need to determine if the fault (voltage failing to increase) is caused by T2 chip data problems.

21. Find the T2 chip on the bitmap, and the location name is U3900. Search U3900 on the diagram and find the ROM chip for T2.
22. Copy signal SPI_SOCROM_MISO. Find the SoC ROM, and the location name is U4770. Find U4770 on the bitmap.

23. Find the SoC ROM (U4770) on the motherboard. Remove the SoC ROM chip with a Hot Air Gun at 430℃.
24. Get the BY-T200 and write the new SoC ROM data. Attach the chip to the seat of BY-T200. Pin 1 of the chip must align with the red dot on the tool.
25. Then connect BY-T200 with the computer.

26. Install the driver and open AsProgrammer.

27. Click Read ID and select MX25U3235F_1.8V.

28. Click Open file and select A1989 T2 ROM original data.bin.

29. Click Auto Program and click Yes.
30. Data writing has been completed.

31. Unplug BY-T200. Solder the chip back to the motherboard.
32. Plug in the power cable. The BY-3200 shows an increase in input voltage from 5V to 20V.
33. The current jump on the DC power supply is normal, which indicates that the motherboard is turned on.

34. Disconnect the power cable and install the motherboard. Plug in the power cable.
35. The MacBook is turned on and can enter the system.

36. Lastly, reassemble the MacBook by following steps 1-5 in reverse.
37. Connect the battery flex cable and put the back cover on.
38. Plug in the power cable and press the power button. The MacBook is turned on and can enter the system. The fault has been cleared.