Warning! This operation returns all settings you’ve made in the menus to their factory-set condition. Do not use this function unless you are certain that you want to do this.
To restoring Suzuki SP-47 to it’s factory settings, just simply power ON while simultaneously holding the [– LEVEL ] and [+ LEVEL] buttons.
Hopefully the article of “Resetting Suzuki SP-47 61-Key Portable Keyboard” can help you.
Reference: Suzuki SP-47 manual