Alvin G - Al's garage band goes on World Tour headbox earth wire mystery

[CliveP]

Hi guys
I bought this machine and in the head box there is the green earth wire. 1 goes to the dotmatrix and the other is loose and I am not sure where it goes?

Can anyone advise where it should attach to? Speaker?

Thank you
Clive

 

[MajesticPinball]

I dont know anything about Alvin G. machines but is there a metal earthing plate in the back that all the boards are fixed to? If there is it should connect to that to ground all of the boards.