chuckey
Advanced Member level 6

Thats the purpose of the linear regulator. To save a lot of time, it would be good to get a PSU with a schematic. This is because the PC itself switches on the main PC, so this circuit could be replaced with a switch, labelled "mains ON/OFF". There is also quite often some sort of interlock , whereby there must be a load on the +5V line before the PSU fires up. But in principle what I have said is correct. When you strip the +12V winding, note the number of turns, because you will need to wind on 85/12 times that number (the extra 5V is to make sure the LM317 has some extra volts to drop to ensure that it regulates) with a wire gauge that will support your current demand.
Frank
Frank