Malfunction Phenomenon
We can turn the volume up and down with the volume button.
In this case, the received iPhone 7 Plus volume down button not working, but the volume up button works normally.
Trouble Shooting
According to the malfunction phenomenon, we can conclude that the problem should from the volume button relevant circuit. First, have a check the diode value on volume button connector J4504, the values are normal.
Then we continue to measure the voltage on pin 14 of J4504, the value was just around 0.8V, which was abnormal, normal value should be around 1.8V as we compared with a normal motherboard.
The problem was from the power line connected with pin14 of J4504.
After checking the schematics, we found the power was from PMU U1801.
We can borrow a voltage of around 1.8V from other components. Here we can jump a wire from pin1 of C2414 to pin14 of the connector J4504.
Test after jumping wire, the volume down button can work, the problem resolved.
iPhone 7 Motherboard Repair Course
