This simple charger was found in a 1980s documentation. The transistor may be the TIP42 with a heat sink. R1 adjusts the load current. The transformer has 1 A of secondary current.
This negative voltage source was found in a Popular Electronics from the 90's. The transformer has 120V...
In this circuit the signal from the phototransistor is amplified by a Darlington stage and then...
This circuit is from an 80's documentation. Equivalent transistors can be used. The circuit is...