375 will lay down sweet MMA runs. Either top right or left of front panel, there should be a black process selector switch, turn this to MMA image. I can't remember if there is an HF selector switch, if there is, turn this off too?
Then at bottom of plant, there are large aluminum selector arms/switches, depending on rod spec, select either ac or dc. It's not difficult to work out really, can't be much more help trying to think of the layout of a plant I have used hundreds of times many years ago.......