I have mentioned this model before. Before the pandemic I picked one up for about £3 at a car boot sale. With Dolby I thought is was worth restoring although I didn't realise how much time and money it would take (quite a few hours and about £20). Once I had worked out how to unclip the back (there are no screws at all just clips in the positions shown) I discovered the belts had turned to sticky black goo. When the back is off make sure you don't loose the tuning knob cover which just slides into slots. If you remove that, and disconnect the tone control flexi cable by lifting up the clip on the yellow connector the the board / mechanism can be lifted straight out of the case. After ordering a new set of belts (for more than I paid for the Walkman) and some IPA to clean of the goo, I spent along time cleaning off the goo then fitted the new belts. Disappointingly I found it was running very slow and the balance was off. Having bought the new belts I did a few searches on eBay and found another WM-BF49 "Buy it now" for less than £10 inclusive so bought that. Opening it up I found that like the first the belts were sticky goo. This time I bought a set of tweezers to help remove the remains but it still took about 30 minutes. Taking the belts from the first unit and fitting them in the second I noticed something important. The belt driving the hubs has to go underneath the spring that pushes the FF and REV buttons back. If it is put over the top it will be rubbing against the spring. This isn't obvious if look at the mechanism from the top. Looking carefully at the springs in both units they seem to have a slight kink in them to give more clearance over the belt. To get the belt underneath the spring just unclip it from the hook nearest the flywheel and slide the belt underneath it. My second WM-BF49 now plays properly, and sounds good. I suspect that the slow speed of the first one was due to my incorrect placement of the belt, although that doesn't explain the balance problem I had. An oddity of these units is that the Tone Controls only work when the "Mega Bass" switch is on, so a more accurate description of the switch is "Tone controls on". Hopefully someone might find this helpful in the future. I'm sure a member like @Machaneus or @CDV can probably give a list of similar "Cheap Sony Walkmans" that use this same mechanism.
Thanks for sharing @Longman . This does look like a cost reduced version released by Sony, not sure how expensive it was back in the day when it was new. No screws but plastic clips make it difficult to service. One can open it carefully, but nowhere as repairable as other series with screws.
