What steps do you have to make after replacing the logic board?

In reviewing the Retina MacBook 2017 Logic Board Replacement guide you’ll see these comments on the last step:

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.

Aaron Dalziel - Apr 12, 2018

While it’s true that the internal documentation specifies this for a 2015, after frying 2 motherboards with a normal charger, I spoke with the engineers and they told me that this also applies to 2016 and 2017 macbook main logic boards. I say- It can’t hurt to try to wake them up with a 5 watt charger first! Please take 5 minutes to save your motherboard.

Noah - Mar 4, 2021

I strongly recommend you follow there advice!