The width of the traces connected the screw terminals are really thick compared to the traces in the rest of the circuit. That indicates to me that the screw terminal side is lower voltage higher current while the other side is higher voltage lower current. It looks like the transformer is used to step up the input voltage. At least that's what it looks like to me. I think one way to figure it out for sure would just be to ask the OP. So talkinggoat, which side is the input and which is the output. Also, are there any markings on the transformer?