Hi, I couldn't help myself and purchased this beautiful looking walkman. I got it for a decent price because it is missing the battery box. Its condition is very good as it can bee seen in the photos. Only weird thing I noticed is that Rev Mode switch is not moving no matter how much force I apply to it but otherwise all mechanical parts seem to be working/moving as they should. But I can't test it since I don't have currently a way of powering it. Can someone tell me which power pin is which polarity so I can give it some power with alligator cables for testing. I am planning to 3D print a battery box and make contacts from a simple PCB. I think it will not worth the effort for saving a bit of money since it will also probably need a new belt and I doubt I will find information about this particular model but I guess I will find out that later. I would really appreciate if someone can provide photos of the original battery box as reference.
Open the back cover, look for the ground plane of the PCB (typically solder mask removed near the holding screws to connect case GND to PCB GND) and measure continuity from the ground plane to both of the pins. Also be careful with testing, as some of these battery adapters may have regulators in them. Start low (like 1.5V-2V) and slowly crank up the voltage on your power supply. Also limit the current to 150-200mA if your supply has a current limiting functionality.
Actually I could just solder wires to there and glue a normal battery holder to the bottom instead of going all the way with 3D printing. Looks like there is a opening at the bottom for wires to go outside as well.