@UniqueUserName1234
I think the SA1, like all the other boards, use a 2.5mm barrel jack, as this is best suited to higher currents.
The 12v rating is only nominal, the barrel jacks can do 24v perfectly well.
But there are low current barrel jacks, up to 2A, and there are higher rated ones, 6A or more.
You need to find a higher rated one, with the connecting cable thick enough for the higher current.
The centre connection of the barrel jack is wired, with a red wire, to the 24v + screw terminal on the PSU.
The outer sheath of the barrel is wired, with a black wire, to the Ground or – screw terminal on the PSU.
The colours of the wires are convention, any other colours will do...
The thickness can be 22-24AWG, or the equivalent for multi-strand wires,, preferably not higher.
The mains power connection wires coming into the iMac need extending to the input of the new PSU.
The original plug that connects to the original iMac PSU input socket has the L (live) wire furthest from the edge of the PSU,
and the N (neutral) connection nearest to the edge of the PSU.
You extend these wires to the L and N input screw terminals of your new PSU, maintaining the polarity the same. L and N.
