MacBook Retina early 2015

ATTENTION: There is a special detail to note for the model from early 2015! After disassembling and reassembling, you MUST connect the MacBook to a low voltage source (5 watts) before using it, otherwise the logic board can be damaged! You will need a 5 watt power supply (e.g. from an iPhone) and a USB to USB-C cable.
For this, connect the cable to the power and the MacBook and wait until the normal beep sounds after about 10 seconds (the screen should also show the charging icon). If the battery is empty, this may take 15 minutes. If the MacBook can then be started normally, it can be operated with the normal power supply.