Though very ancient, it still is many useful.
it is the well-regulated power supply. We use it as the simple step down 12v to 9v converter circuit. It can give the output current up to 4A.
Modify power supply source in old circuit PCB. I then build to is 9v regulated power supply circuit , that can give current 1 to 2Amp. Look 3 circuit below
This is 5V low dropout regulator circuit using transistor and LED only so easy,lowest voltage input is 6V so across it is 1V only, make output is 5V 0.5A