This circuit was found in a 1965 Electronic Design. Transistor Q2 must be load dependent. The circuit can be adjusted for currents from 1 to 10 A. The voltage drop is 3 V and the maximum voltage is 35 V.
This circuit triggers the LED when the monitored battery voltage drops below 9 V for 12 V...
We found this circuit in a Radio Electronics from January 1967. The SCR is already the C106, which...
This power source with silicon diodes at a time when valves were still used was found in Radio...