Fried auxiliary LED pin

[IceAndNull]

So I was connecting an arduino to my MA2 through a mod I made a post about and, without paying attention, hooked it up with the wrong polarity. It was connected to the auxiliary LED pins at the time but they were off, however it still fried the positive pin. My guess is some current went backward through it. I don’t expect anyone to have any idea what burned out but if anyone has any idea or knows of a circuit diagram of the core board it would be appreciated.