[sdiy] Strange fault on Roland/Rhodes MK60

[Tom Wiltshire]

I've got a Roland (Rhodes) MK60 with its guts out on my floor at the  
moment. When it came to me it wasn't doing anything. It long ago lost  
its buttons (the plastic buttons get pushed down inside the case and  
then get lost) but was previously perfectly functional, as long as  
you had a screwdriver to poke the switches through the button holes.

I checked the switches over, and a good number are broken (make no  
contact when pressed). Replacements are on order. Also there are two  
dead notes on the keyboard (although I've taken it apart and cleaned  
up the rubber contact domes, I still can't make them play).

All of that I regard as pretty much run of the mill for a keyboard of  
this age. The strange fault, though, is the intermittent one.  
Sometimes when  you switch it on, it works ok (but rarely). Sometimes  
it does nothing (as it was when it arrived). Sometimes (mostly) it  
goes into some strange state where the "Down" button LED lights up  
and it plays a single note constantly whilst ignoring the keyboard  
completely. Pressing other buttons changes the pitch of the note, and  
some button presses turn it into a "beep beep beep" instead of a  
constant note. Might this be some strange test mode? How would I find  
out? How do I get it to go back to normal?

Any ideas appreciated. This list has had some notable successes  
recently!

Thanks,
Tom