With this circuit it is possible to obtain a voltage of -5 V from a 5 V source. The circuit is from Radio Electronics from May 1982. The maximum current is around 80 mA.
The oscillator shown in the figure generates a rectangular signal with a 50% active cycle (square)...
This power supply can be implemented with a TIP32 providing an adjustable output at the 2k2...
This switched circuit was found in an old documentation and no information about the transformer...