Memorex made a radio? If that radio is 13 years old and still working, consider yourself lucky. Anyway, you may have to pull the unit and see if there is a blown fuse. You may have a unit that has two power feeds. One constant feed that keep the clock alive and another (switched or constant) that provides power to the rest of the unit.
2017 Ford F-250 6.2 gas
2018 Jayco 28BHBE
US Army veteran