1980s kit CK1010
This preamp has has total rebuild of the PCBs, new connectors and controls. It is later model with a CD input added.
The power supply for this preamp is inputted via the DIN socket, If uses as a standalone unit, the phono output can feed signal to the power amp, while the DIN socket is used solely to connect the PSU. It was originally intended to be powered by a 20mA constant current source. This would provide the 10mA for the PCB and another10mA for the shunt regulators. The early PCBs had zener diodes as crude shunt regulators and are not ideal. It would be better to supply the PCBs by means two series regulators such as LM317 and LM337 from a raw DC of +/- 25V. The output voltage should be set for +/-9V up to +/- 11V to stay below the zener voltage. Alternatively remove the zeners from to PCB to use up to +/- 15V for the PSU.
It is best to change the LED from red to green as this suggest a standby mode which it does not have.