Hello, I have a whirlpool oven model GBS307PDS7 that's about 10 years old. When attempting to use it cooks for about 30 to 45 minutes then completely looses power. The display is completely blank no lights are on and it will not respond to any commands. After about an hour it comes back up with error code PF. Then you can restart the unit, but it will only operate for a short peoriod as previously stated. Not sure where to go from here and any help will be greatly appreciated.... Thanks!!!