Motherboard No.: 820-00239-A
Malfunction Phenomenon: Macbook A1706 couldn’t be truned on when press power button, but there was current when plugged in power cable.
Main Reson:
There might be some problem with start up circuit;
There might be some problem with the sleep circuit;
Troubleshooting:
We removed the back cover and disconnected the battery, connected with power cable and power on, macbook was truned on normally, all functions works normally after we tested. We truned off the macbook and tried again, it worked normally.
After we turned on and turned off the macbook twice, it was normal. So we doubt the problem was from the battery?
We connected with battery and power cable, the macbook was turned on automatically, all worked normally. There was no problem after we tested several times, so we left the macbook at the side.
Severl minutes later, the screen was truned off, we press the capslock key, there was effection, it means the motherboard was working normally, but the screen was turned off. We tried to press the power key to turned off the macbook, but it was useless. We have to remove the back cover and disconnect the battery to turn off the macbook.
After that, we tried again as the following steps,
Normally, when we open the screen for A1706, the macbook will be turned on automatically even we do not press the power button.
We connected with power cable, openned the screen and pressed the power button to trun on the macbook, and then closed the screen and open it, pressed the power button again to trun on the macbook , it couldn’t be turned on, and there was no response even we pressed any keys.
According the two test, we could concluded that the problem was from the sleep circuit.
We disconnected the power, took out the motherboard, and found out the sleep connector, there are two connectors on the motherboard, one is ont the right side, the other is on the left side,
we call them HALL Effect Pads.
After we checked the two switches, we could see the one on the right side was corrossioned very seriously. We opened the bitmap and schematic, found out the sleep circuit.
SMC_LID is the sleep signal, it controls the sleep function. If this signal is abnormal, the sleep function can not work normally or can not be wake up. We checked the voltage on the line of this signal, the value was 0, normal value should 3.3V. We replaced the corrosioned sleep switch J5260 with a new one and check the voltage on again. It was still abnormal.
We traced the rail of SMC_LID, it was powered by PP3V3_G3H_SMC_ISNS via a pull-up resistor R5171.
We checked the voltage on pin 2 of R5171, the value was 3.3V, which was normal. SMC_LID is
from U5255, before SMC_LID, the signal HALL_SENSOR_LEFT and HALL_SENSOR_RIGHT should be there.
We checked HALL_SENSOR_LEFT and HALL_SENSOR_RIGHT by measuring the voltage on pin 1 of R5251 and pin 1 of R5261, the value on R5251 was 3.4V, which was normal, but the value on R5261 was 0, which was abnormal, we can concluded the problem was from the rail of HALL_SENSOR_RIGHT.
We continued to trace the rail of R5261, it’s connected with sleep connector J5260 on the other side of motherboard.
We checked the voltage on J5260 of HALL_SENSOR_RIGHT, the value was 3.4V, which was normal.
Then we checked the diode value of HALL_SENSOR_RIGHT on the same test point. It was 448, which was also normal.
Until then, we can concluded that the problem was from R5261 or the line bettwen R5261 and J5260, we continued to check the diode value bettwen pin 1 of R5261 and J5260, the value was infinit, it was opened, that’s the problem!
We could see the line bettwen R5261 and J5260 is too long, so we can jump a short wire bettwen pin 1 of R5251 and pin 1 of R5261.
After we jumped the wire, we check the voltage on SMC_LID agian, it was 3.4V, back to normal.
We assembled the macbook and tested again. All functions were normal including the sleep function.
Summary:
Sleep function was abnormal because of the sleep switch was broken and the line of HALL_SENSOR_RIGHT was open, we replaced a sleep switch and jumped wire bettwen R5251 and R5261, problem resolved.
