My Neff C4EE HOB has 2 small rings which no longer work?

Hi all. Can someone help? I have a rather old electric Neff Hob model C4FF which has 2 large rings and 2 small ones. Both the small rings have stopped working (no light idicators or heat). Both rings stopped working at the same time so I think it might be a fuse. I've tried to find fuses but can't find any. Does anyone know where I can find the fuses?