This is a high quality power supply with a continuously variable stabilized output adjustable between 0 and 30VDC. the LM 723 is the heart of the power supply which drives the BD137 and then the 2N3055. The circuit provides short circuit protection. And has great stability at voltage changes.
Drive the circuit with 24 Volts 3A from a transformer. the 2N3055 needs a good heat sink.