jones z620?

i was given ajones z620 an old machine but seems to work ok.BUT the straight stitch the needle is to the right not central how do i align the needle to center. there are two knobs to the front top with 1-5 and 1 is the straight stitch and the others are zig zag with abutton in the middle. if you can send me your e mail i will send you a picture and you can see the outlay of the machine.