You never know what you're going to get when you buy something that's listed as "unconfirmed" or "junk" on Buyee - especially if they haven't even tested if it powers on!
In this case, I thought it might be worth the risk for two MiniDisc devices, especially since one was a Sony MZ-N1 - one of my favorites and a Sony flagship portable recorder (from two decades ago).
The first thing you'll want to check is power - via a gumstick and an external battery pack. If one of those power the device, then you'll know what the next step is.
For example, if the gumstick doesn't work, but the external battery or power supply does, then you might just need to clean the battery contacts at the door or internally.
In this case, I cleaned the battery door contacts, but it still wasn't powering up properly. Check out the video for a quick fix that I didn't expect.
Also, at the end of the video you'll see my other Sony MZ-N1s with dock adapters. These are very useful if you don't have the original dock since they will allow you to use a modern USB-C cable to power and connect your device for NetMD writing! You can get one with or without a battery from MDGadgetry (@mdgadgetry) on Instagram!