If you are replacing the logic board once the machine has been rebuild the 2015 model has to have a 5W power adapter plugged into the machine first before the full 29W power supply otherwise there is a risk of damaging the logic board. Once the power is supplied the battery disconnect LED will switch on and once this has occurred you can remove the 5W and supply the machine with the full 29W power adapter.
Before the IPD flex cable can be removed the battery disconnect button has be held down for up to 10 seconds. If the LED near the battery connector is switched on it shows that there is power going through the logic board from the battery, once the button is pressed and this light goes off the machine is safe to be worked on.
Before any repair is carried out that involves removing the bottom case, the machines auto-boot function has be disabled. This can be disabled via the terminal command “sudo nvram AutoBoot=%00” once the repair has been completed the auto-boot function can be re-enabled via the vermin command “sudo nvram AutoBoot=%03”.