- Make sure there is no floppy disk in the disk drive.
- Turn off the power.
- While holding down the [One Touch Program] button, press the [Power On] switch to turn the power on.
- Continue holding the [One Touch Program] button until 'Factory Preset is Loaded.' is displayed.
- Never switch off the power while this operation is in progress.
Source: AT 90s — at-90s-80s-60s-om (manual)