This is in three parts. Firstly the factory OS needs to be reloaded and then the sound banks & global data will have to be restored from ROM. Please note that it is unlikely that the factory OS should ever need to be restored. Any problems which require a "reset" can usually be overcome by restoring the global data and / or the sound banks 1&2.
A-Station Factory installed O/S Restore
Turn on with "demo" held down and keep demo pushed in. Screen should show "FA OS" for factory OS. Press select and now let go of both buttons. "Su rE" should be displayed. Pressing select again should restore the OS.
A-Station Bank Restore
Enter the Utility mode. Press the "+" button to unprotect the unit. When restoring banks of factory programs, the program entered before the utility menu was entered selects the bank the restore will go to - ie if program 152 was selected, B1 or B2 will be restored to Bank 1. For an A-Station to be completely reset, B1, B2 and globals need to be restored individually, there is no total data restore. The init banks 3&4 are not stored in the A-Station ROM.
A-Station Global restore
Press "9" to enter the restore menu. The options are "1P, B1, B2 and GL" on each successive press of "9". If GL is selected, press "+" makes GL flash, press "+" once more performs the restore. The unit will automatically write protect itself as this is one of the restored global settings.