probably bad 12v connectors between the rectifier board and top right plug on driver board

What do driver board test points read?

As barakandl says then, the 12V isn't getting from the rectifier to the driver board to be regulated down to 5V.

it usually a 12v return orange wire that burns.

get the manual out. wire diagram page. repin the top right driver plug and and the 20 pin rectifier plug. If the 12v return connector is toasted, the others probably need attention too. Check the male pins too for broken solder joints or tarnish/burning.

go to pinwiki. see ground mods for driver board.

the orange wire is the isolated 12v return so it should be at 0v. sounds like it is floating.

do the pinwiki ground mod and rebuild your plugs. If the female side burned, the male side needs replaced too. The male pins can have cracked solder joints.

Your 5v power supply on the SD board is not functioning. 12v unregulated in, 5v DC out. Fix that first. Pull the schematic. Check the connectors for open solder connections on the pins. If the large capacitors are original replace them.