Most likely Roland has printed everything you need to know on the back of the keyboard. It will say something like 9v 400ma. This means you need a 9v power supply that puts out 400 ma. You can find one of these anywhere. But take heed, they also show on the diagram that the inside is positive and the outside is negative. Be 100% certain you've got that right before attempting to use another power supply. The manual will also have some info for you.