This circuit was obtained in a 1989 English magazine. Despite using a fixed 5 V regulator, it can provide outputs of 5, 9, 12 and even 15 V. The maximum output current is 1 A, and all components are common. The transformer is 12 V x 1 A, and the bridge diodes can be 1N4002 or 1N4004. It is not necessary to use a two-winding transformer. Just use one that has a single 1 A winding.
