This circuit was found in documentation from the 1970s. However, it can be implemented with modern transistors such as 2N2222 for Q1 and BF494 for Q2. The crystal depends on the desired frequency.
This circuit was obtained from an old American documentation having a limited adjustment range....
In the figure we have a way to obtain a 15 V symmetrical source with a 30 V single winding...
This circuit was originally designed to maintain the temperature of a brooder at 41º C. However,...