Ok looking at that then the original transformer is being used to power the original board at the top. The transformer says 28V (this is AC voltage) which is about right for the drives ending up around 36V when rectified.
The original board will also probably transformer it down to 5V and that's where the BOB is getting it from. Trace the wires from the 5V terminals on the BOB and you'll probably find they route back to this board.