Thanks everyone for your replies (although I wasn't expecting so much sympathy for Yamaha).

Just as a followup, I acquired a replacement din cable from another electronic component (a DJ dual cd player). The pins are wired straight across. There is nothing "heavy duty" about the Yamaha cable. I had the end of the wire cut off to confirm this.

I tested it and it works fine. I used small strips of gaffers tape to attach the din cable to the signal cable around every six inches, the same way that Yamaha did it.