Not familiar with this equipment, but this might help. Normally on the circuit boards there is a reset button of some kind or a jumper (a connector) that you kind connect to reset to factory settings. There might also be a sequence of steps that you have to perform, like holding down knob x while you power up. Do you have a manual for this machine - if not you should be able to find one on the web somewhere that should tell you how to do this. Try disconnecting the battery again and wait about 10 secs or so.
Found this http://music.manualswarehouse.com/mang002.htm
Found this http://music.manualswarehouse.com/mang002.htm
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