Wow - great

Looks like the long wire is to the SIF point but I am struggling to find where the wire from the black power cable goes on the circuit board

Wonder if it redundant?

3 power wires are soldered into the connector from the PSU

Red - goes to +5v
1st black wire - but connects to nothing
2nd black - no soldered wire
yellow - goes to +12v DC

any other power input - looking at the schematic but struggling a bit. Cant see why someone would solder in a wire and then not use it.