Exact same year, exact same model, and the exact same problem just happened to me. The circuit board is the 6600-286 which is also used for the Jucuzzi J-300 series spas. In my case the circuit breaker started tripping about a week or so ago. I kept resetting it, and finally one time a few minutes after resetting the breaker, I hear a "zzzz" sound and the breaker blew again. This time I pulled off the side pannels and saw the damage. I clearly shouldn't have reset the breaker after the first time it blew. The connector to the white (yellow?) wire of the "Heater Out" relay was completely melted off of the board. At this point I figure I'll need a new board, and my guess is the original problem was that I need a new heater element... I'll attach an image. Just promise not to remind me how stupid I was for resetting the breaker - I realize that now...
-Scott