This circuit, from an old Argentine publication, uses a slightly different symbology than we are used to. It is a small 0 to 12 V x 500 mA power supply, if we use a BD136 with a heat radiator instead of the original transistor. The transformer is 12 + 12 V or 15 + 15 V with 500 mA and the diodes can be 1N4002. The potentiometer must be wire and R3 is 5 W.