The machines will have been put together by unskilled people.
The designers will have arranged the circuit board and the cable connectors in such a way that makes it impossible to have a wrong connection - at least this is what they should have done.
Test the theory - with the machine unplugged take any connector and see how many cables will mate with it - my guess is only one. Take a second and a third and do the same.
And you're right - get it wrong and the machine would be damaged - the manufacturer would not want this happening in the factory.
Good luck...
Jack Ruby, September 2014