Parts list: TR = 2 x 15 volt (30volt total) 6+- amps D1...D4 = four MR750 (MR7510) diodes (MR750 = 6 Ampere diode) or 2 x 4 1N5401 (1N5408) diodes. F1 = 1 Amp F2 = 10 amp R1 = 2k2 2,5 Watt R2 = 240 ohm R3,R4 = 0.1 ohm 10 watt R7 = 6k8 ohm R8 = 10k ohm R9 = 47 0.5 watt R10 = 8k2 C1,C7,C9 = 47nF C11 = 22nF C2 = 4700uF/50v - 6800uF/50v C3,C5 = 10uF/50v C4,C6 = 100nF C8 = 330uF/50v C10 = 1uF/16v D5 = 1N4148, 1N4448, 1N4151 D6 = 1N4001 D10 = 1N5401 D11 = LED D7, D8, D9 = 1N4001 IC1 = LM317 T1, T2 = 2N3055 P1 = 5k P2 = 47 Ohm or 220 Ohm 1 watt P3 = 10k trimmer This is definitely an simple to create power supply which has reliable, clear and regulator 0 to 28 Volt 6/8 Ampere output voltage. By using two 2N3055 transistor, you'll get two times the amount of electric current. Although the 7815 power regulator is going to kick in on brief circuit, overload and thermal overheating, ...