I have a 15-91 that was once a cabinet machine. The controller wires had been cut so the lazy so & so's could removed it from the cabinet. I said lazy because to properly remove it they'd have to unwire the controller or the cord block.
So if it's the controller wires that were cut, that's a good possibility.
Sew-Classic has the power / controller cord set, or the individual cords and also the controller depending on how you want to wire it.
Joe