You could create one DC main supply and then use multiple LM317's to do each voltage.
You'll have to watch the power dissipation in each LM317 however because they will get hot if there is significant current draw.
As Mr Al said, you need to watch the power.
Say you need 12V@1A, and 0.5A in the 5 other supplies. If you run each one in turn the 12V supply is passing 3.5 A (1A it's direct load plus 0.5A * 5 for the others). If the input voltage is 24V then it must dissipate 3.5A * 12V = 42 watts. PLUS each regulator is also burning off power for a total of 60 watts.
60 watts is enough power to light a room. Note no matter what you do (assuming you use linear regulators) this same power must get burned off as waste heat somewhere.
When you run all the regulators off the 24V input you just shift power from the 12V to the others, so the 12V now burns off just 12 watts but the 1.5V regulator goes from 5.25 watts up to 11.25 watts.
Can you still get the 5A regulators in the old style TO3 metal can?The lower you set the output voltage, at any given output current, the more heat the poor LM317 has to get rid of. One of my first power supply projects back in the 1970s was a small AC Variac ahead of a ~28V transformer driving an adjustable regulator that had fold-back current limiting and was adjustable from 0 to 30V.
I used the Variac to reduce the rectified-filtered voltage upstream of the regulator to where the power dissipation in the regulator element was manageable when the supply output was only a Volt or three...
Still have that supply, and still use it...
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