The M20 is a bit of a different animal than a regular ADAT; there's a lot more stuff jammed into that box including a more robust transport, and, there were not a lot of them manufactured. I'm not confident your standard ADAT tech could handle it. I used to have a copy of the service manual but I sold it on Ebay a few months after I sold my M20. That was about 18 years ago. There is a former Alesis ADAT factory tech at Audio Design in Burbank CA. You might want to check with them.