I have a DVC-500, and so does my brother in Maryland.
Both control boards failed, due to bad potentiometers.
Mine just out of warranty, (1 or 2 months) , Harman supplied the part at no charge, I installed.
His failed in warranty, and was covered, he installed it.
I bought from Rella in L.I., NO ONE else had a stove to sell 5yrs ago in my area (BIG DEMAND)!!!
I kept the old board, even though it was requested back.
I found , and bought 2 sets of pots off ebay,(he threw in a 7th for free).
I gave a couple to my brother Today as spares.
It was the STOVE TEMP pot that failed.
Running as I type this.