Factory Reset Procedure:
Oberheim Matrix-6:
Pressing the STORE button while powering up (factory reset).
Then, download the factory patches as an mp3 stream that do the trick.
Yamaha S90:
WARNING: All user stored data will be deleted. If the current settings and data are not expendable, create a backup before executing the Factory Reset procedure.
1) Press the [UTILITY] button.
2) Press the [JOB] button.
3) Press the [ENTER] button.
4) Press the [INC/YES] button.
Yamaha MU90
Turn the power OFF, then Power ON while holding UTILITY & ENTER.
Roland U-110
hold the edit and part buttons and power on. / To reset this module to its default settings hold down [part/jump] + [edit/exit] when turning the unit on.
Roland DEP-5
memory no up and down + power on