Reviving A Boss DR-660 Drum Machine

I bought a used Boss DR-660 Dr. Rhythm drum machine (manufactured in 1989) on Reverb a while back, and it arrived. I originally bought one of these around the year 1992 or 1993. It was my main source of drum sounds throughout the 90s. It was packed well, so I was optimistic. I even got a nice note. Confusingly, and ominously, it came with a fresh coin battery. After unwrapping, the device was in…