There are a lot of power supplies published over the years.

Here is another one. It is remarkable because it can be regulated down to 0 volt with only a good old LM723. No need for an extra (negative or floating) power supply. It was presented to me for a repair and I was happy to get the schematics together with the equipment. My first reaction was just surprise. How does this work?

After adding the functions of the pins of the LM723 to the drawing it slowly became clearer. To understand the schematics we must rethink the concept of power supply.

 

It changed my view on power supplies.

 

I will discuss here only the power supply in the top half of the original schematics, not the voltage and milliamp display in the bottom half of the original schematics.

 

Many thanks to the people of the ROVC which permitted me to publish this design.