@leecc73
Thanks for the photos.
I think the brown and blue cables are "live and neutral" come from the AC mains IEC socket, the small transformer is connected to it via a resettable fuse (F1), and the K4 is connected to the front panel power switch.
When the front panel power switch engaged, RELAY1 energized and close the contacts to power the main transformer.
I believe Accuphase made three versions of this board for 100V, 120V and 220/240V mains. If you want to convert to different mains voltage, a new board or install a small transformer with correct primary winding for the applied voltage is needed.