MacBook A1502 No Charging and Keyboard Not Working Repair Process.
Model: A1502
Board No.: 820-4924
Defect Phenomenon:
- Connect with DC power, the green light is not on, and there is a current value on the DC power supply. Detach the DC power supply, the battery can discharge normally.
- Enter into the system and test function, find the ‘7 U J M’ 4 keyboard button not working
The motherboard looks fine on the appearance, there’s no water damage, not been repaired before.
Repair Process
First, repairing the power indicator light not turning on issue.
Pin #6 of J7000 is the green indicator signal pin, tested by the oscilloscope there is a 16 volts voltage, which is abnormal. Normally, the voltage on this rail should be around 3.3V. It should be the power cable with a problem.
Replace it with a new one, then the green indicator light works normally.
Then let’s repair the keyboard issue.
First, replace a new keyboard to test, the issue still remains the same. So the problem must come from the motherboard.
And only a part of the keyboard buttons failure should be caused by one specific signal control rail abnormal. We can start from the keyboard connector, and measure the diode values on the pins. After measuring, all the diode values are OK, there is no rail broken or components short, missing, etc.
Then find out the keyboard control chip U4830. It is a QFN chip, and check from the cosmetic, everything looks fine. We can replace it with a new one, however, there is no spare chip for replacement, so let’s just continuously patiently check.
Check the connector pins’ diode value again, when measuring the diode value on pin 12 of connector J4813 (WS_KBD17). It’s abnormal, not connected with flex cable.
Carefully check the pins, everything looks fine. Then check the buckle， it’s found the buckle with a problem.
Actually, the keyboard issue caused by the buckle is not so common, here is a special case.
After replacing the buckle with a new one then testing, the keyboard function back to normal.
