The JP382C is the CNC control board. The two boards stacked together are the 4th axis and Spindle board. Top one JP1635A is 4th axis the lower JP1482 is the Spindle/Power board.
This board rectifies the AC power from the transformer for the drives, The fans, and the Spindle. As well as doing the PWM for the spindle and from what I can tell the Spindle is 54Vdc. The Drives are 27Vdc, which fits with the TB based drive Chips. Here is a link to schematic for the Spindle board.
https://hackaday.io/project/6776-304...ller-schematic

Unfortunately, I haven't yet tracked down the pins you need but I will bear with us.