If it's not used a long time, you probably will need to spray all pots and contacts.

That's all I ever had to do a shortwhile ago.
Which is pretty good as I am the first owner since 1984/85 . (not sure about the exact date, will have to look on the invoice)

The S612 never needed any maintanance.

The md280 is still ok, but all the disks are
at the end of their life..
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Keyboards/Sound Units: Kurzweil 2600S, Roland VR-760, Acces Virus C, Roland G-800, Akai AX60, Minimoog, Machine Drum, Roland R8-M, mediastation x-76