This is circuit Variable Regulator power supply,Output voltage 0-30V and Current 5A max. Use IC LM723 is a voltage regulator designed primarily for series regulator applications. By itself, it will supply output currents up to 150 mA I so use Transistor 2N3055 X 2 for Booster current to 5A. IC CA3140 for Control Current and Voltage.
P1-50K for control current.
R20-50K for Adjustable voltage output.
R19-5K for fine Adjustable voltage output.
Transformer use 5-8A, Voltage see in circuit.
Detail more see
PCB Variable Regulator 0-30V 5A