Today I seeks variable power supply circuit come to deposit again. Which be the circuit that use base equipment, build not difficult follow the circuit can fine volt get 0-30V , give current get about 1-2A depend on transformer at you choose to use. The prominent point of the circuit use transistor join a pin BE replace Zener Diode. Then get around problems about seek buy Zener voltage that can’t want. By transistor at use 2N3638 numbers or the number replaces. For transistor output use 2N3055 durable numbers current not exceed 2A. For other detail , request friends , see in the circuit better.