More of a "servicing" video than a repair, but if you haven't seen the insides of a Sony MZ-E75, check it out!
The Sony MZ-E75 from 1999 is an SP-only player with a neat trick: It has two headphone outputs! It has the usual one by the remote jack, but it also has another one on the side for listening with a friend.
I could see this also being used a cheap "line out" for another set of speakers or even for a BT transmitter so your friend could listen wirelessly!
This one came unconfirmed and had an old corroded gumstick in there. I couldn't test it with AA batteries since these older Sony models had a different sidecar contact spacing than the ones I had...
After some opening and cleaning, it was back in action!