This is a simple zener diode regulator circuit ,Simple Fixed regulator, multiple output voltage are: 12V, 15V, 30V
This is dual 15v power supply schematic, using LM7815,LM7915,and power transistor and zener diode for voltage stable voltage 15 volts positive and negative. [...]
This is a 15V DC Regulator circuit at 400mA using IC-748 and 2N3055. Although it is an ancient circuit, but if you have the equipment ready. we may try to build it.