"To restore the Mustang amplifier to factory settings:
1. Turn the amplifier OFF.
2. Press and hold the EXIT button while turning the amplifier ON. Continue holding the EXIT button until it is no longer illuminated.
The FACTORY RESTORE function will erase all user modified presets. It will also restore the AMBER bank of presets and any effect selections that have been modified using Fender FUSE software."
dixit le manuel.