While working on my Roland D20, I believe I may have disturbed or erased something very basic and/or significant. The error message I got when "booting up" with Tune/Function and "Write" pressed simultaneously is "MAIN BOARD ERROR." Does anybody have any ideas about what I may have done and, more specifically, how to fix it? I have a service man who will be able to check it out on Monday, but don't know how I can ever draw on enough patience to wait until then. HELP,Anybody?????