hi , we own a kenmore elite speedcook oven micr./conv., a while back we used the conv. oven set on 450 degrees and had a total unit power failure , so i replaced part no. wb21x10054 i now have power but can only run oven less than a minute or will have unit totally shut off , then a short period later usually less than a minute unit will click on power up and display reads power failure, we spent over 600 dollars for this oven really want to repair it any information would be greatly appreciated thank you jc