Siemens HB903?

HI Rita, it will be the heating element that has blown. If you are practical you can replace it as follows... ISOLATE THE OVEN FROM THE ELECTRICAL SUPPLY, remove the back panel inside the oven, you will see the circular element, undo the 3 screws holding it and GENTLY ease it out so the wires do not pull off, change the wires 1 at a time to the same position on the new element and refit. cheers

Kenjo
July 2014