This is 1.5V-25V DC Variable Power Supply. The power supply use KR142EN14 or LM317 as regulator component . KR142EN14 or LM317 is capable to handle electric current up to 2A. You may use LT1083/84/85 to handle electric current of 7A/5A/3A. Resistor R9 is used as a current sensor to an ammeter. Components list: R1 : 4K3 R2 : 18K R3 : 100 R4,R8 : 100K R5 : 1K R6 : 240 R7 : 4K7 ( Variable resistor ) R9 : 0.33 E C2 : 0.1uF C3 : 10000uF/40V C4 : 100uF/25V D1 : KY202 D2 : KD521 D3 : D311 D4 : KC147 T1 : KT814B T3 : KT209 T4 : KT3102 IC1 : KR142EN14 (LM317) Circuit source: 1.5V-25V power supply with preregulator