Found in a 1960s RCA manual, this circuit uses components from the era. For the indicated circuit R1 is 28ohm and R2 is 1 k.
We found this circuit in a Popular Electronics of the 90s. The circuit still uses light bulbs, but...
This circuit is from Linear Technology 2005 documentation. The circuit is based on company...
The integrated circuit used in this power supply is no longer very common in power supplies today....