I know its an old post but I have been searching for ages for info on this. All my searches bring me back here so it might be useful for other people with the same problem. I eventually worked it out for myself. You have to desolder and remove the transformer from the board. Then solder a couple of links in as per the photo attached. Its important to get them the right polarity. Viewed as per the photo -12v is on the left +12v on the right.
Don't forget to relabel the controller as converted to 12V. accidentally connection to mains would be dangerous.