I need to replace the thermocouple on a triple burner and on a medium burner on a Smeg opera A2 manufactured in 1999. I can get the top of the cooker up for access but cant see how to remove the old thermocouple. I have undone the two nuts on the one for the rapid burner but the thermocouple wont budge up ur down. Is there anything else holding it in place? For the medium thermocouple I cant see how this is secured. Appreciate any help. Thanks Allan