I take out my trusty old DR-660 drum machine from time to time especially for acoustic drums. The acoustic drum samples always sound great to me. I am not sure how Boss/Roland did this in 1996 but the pitch-shifting sounds extremely natural. So tuning a cymbal on the DR-660 actually produces a cymbal sound instead of a high-pitched blip or a low-pitched car crash sound.
Alas when I recently turned it on, it said Battery Low! It should probably say Battery Dead! instead. It turns out I needed a 2302 coin battery for replacing the old one, and a few simple tools.
There are two useful videos on Youtube for this repair. This one is more detailed about opening the 660 (https://www.youtube.com/watch?v=fFIlnb0GHKk). The second one is very brief but shows how to “hook” the battery out from the far side (https://www.youtube.com/watch?v=1nxEHPCfyG8). I used a small L-shaped Allen wrench to hook the battery from the back. Then I used a needlenose pliers to set the new battery in place and pop it in. I powered up the 660 and there was a message something like Backup NG, Press Enter. NG I take it means Not Good. The manual said this error was due to the memory being lost. Pressing enter re-initialized the 660.
Fortunately I had backed up the 660 some time ago. I use a program called C6 for a lot of my MIDI activities. Transferring the back up to the 660 using C6 did not work. The 660 just sat there and did not respond. A second program called MIDI OX did the trick. When sending the back up, the 660 said Receiving Sysex. A short time later the 660 was back to its old self.