Well its about time I put this out there...
I recently got my hands on a Sony MDS-JE530 deck. In terms of the main functionality, it is absolutely fine, except that it won't take any signals coming from my MacBook, whether by coaxial or by TOSLINK. For the former, I used the digital out from a Tascam US-144 Mk2 interface. For the latter, I used a minijack converter and a brand new Fisual interconnect, which was lit up at the MD end during operation. No amount of software configuration changed anything, the deck just displayed a C71/Din Unlock error. Keep in mind that I had a broken CD player lying about, of which the MD Deck recognised by the coaxial input.
So, what is exactly is going wrong here? I'm planning to invest in a Muse USB to SPDIF board so that I can use my ThinkPad with Linux with the unit, but I don't want to waste more money when I find it doesn't work. This is pretty much my only use for MiniDiscs at the moment, so if anyone has any suggestions I'd be very grateful.