Notice that I didn't call this a repair video... Unfortunately, this beautiful Sony MZ-E10 is just as non-functional as when I received it.
The Sony MZ-E10 (late 2002) was the thinnest and lightest MiniDisc player at the time. It's a stunning device that's so thin, Sony designed a proprietary connector for the remote (which then had a proper 3.5mm headphone jack). It had a special dock for charging, and a joystick controller for navigation.
Unfortunately, it was so thin that the board would sometimes flex and connections could break. It's hard to find a working one these days and the ones that are can still be very fragile. I remember some posts by a Korean super-fan that had more than a dozen of these devices stored in various states (battery switch on or off) and many of them were randomly dead after sitting in storage.
I will note that the User Manual (and logic?) can make it seem like you can slide the battery out of the side door, but in reality, it's quite a bit harder than that. I've seen posts where people say they've done it, but I've also seen ones where owners say it's just easier to open the whole thing up.
After making this video, I tried to only access the battery from the side door and I didn't feel comfortable forcing it any more than I already did. I then proceeded to take the whole thing apart again (like in my video) and it wasn't terrible. I figure if I can ever get a working device, I'll try that route again. If I ever feel bored enough to try again, I'll post an update!
Either way, it's a beautiful device! If you follow the MiniDisc wiki link, you'll see the manual which has detailed instructions regarding opening the device. If you'd like to see my video, it's right here!