This is a diagram of a 1970s reel or tape recorder. It is an Italian Geloso recorder, quite popular at the time. The circuit is a reference for equipment recovery.
Found in old American documentation, the components used are still common. The circuit directly...
Found in a 90s documentation, this circuit makes use of D1, a switching diode that is uncommon today....
This filter, found in an old manual, has characteristics of reduced overvoltage given by the graph...