Maker Factory ELECTRONICS EXPERIMENTS BOX Manual page 268

Circuit 63 – 65: If the output voltage drops, T2 receives less control voltage, thus becomes less conductive.
This increases the control current of T1 and consequently T3. The higher current flow through T3 increases
the output voltage to the extent that the old value is restored.
270
Fig. 3.62: Circuit
62: DC-DC converter
9V to 75V
Fig. 3.63: Circuit 63
– Stabilizer for 1.0 V