This thread will cover how to disassemble and lubricate the motor on SONY WM-EX/FX/GX series. Note that there are many types of motors used in these series, but they are all similar on design, based on 2 neodymium magnets and a PCB with coils sandwiched in between. It is typical that these motors come dry from the factory, so it is always a good idea to lubricate when you replace the belt. This and the lubrication of capstan bearings are the 2 most important things that will prolong the life of your WM-EX walkman. When the motor is worn, rotor will have lateral play in the bushing. Result: the motor will be noisy and wow&flutter will higher than normal. In time, the motor will have more and more play in the shaft, eventually leading to a complete failure. The disassembly of the walkman cover and PCB removal are not covered in this thread, but are necessary in order to get to the motor. STEPS: 1. Remove the motor from the chassis. 2. Using 2 plastic spudgers, remove the top magnetic disc. Pay attention to line up the hole of the disc with pulley, otherwise it will get stuck in the pulley. 3. Using a sharp tool remove the glue that attaches the coils PCB to the outer cage (marked red). Pay very careful attention, as there are very thin traces close to the edge. 4. Desolder the outer plastic part with pins from the PCB (marked green). 5. Remove the PCB. 6. Remove the rotor. 7. Clean the shaft of the rotor and the inside of the bushing with a cotton swab immersed in IPA. 8. Put oil inside the bushing. I recommend using watch oil. Make sure it gets to the other side, on the pastic plate. 9. Put grease on top of the bushing, where it makes contact with the rotor. I recommend using a very thin grease, like SW-92SA or similar. You can put oil if you don't have thin grease. 10. Reassemble. You will need to put 2 small drops of super glue on the PCB on opposite sides, otherwise there's a change PCB will come in contact with rotor.
Want to add some clarifications, especially in regard to points 3 and 5, as these are the most diffcult from the entire process. 3. When removing the glue, you need to be very careful to not damage the coil traces. A sharp metal tool is needed, like the tip of a pair of tweezers of a very sharp blade. However don't freak out if some small chunk of the PCB breaks off, that tends to happen but traces will remain intact. Heating the chassis with a soldering iron will also help in softening the adhesive. 5. After the visible glue has been removed, the PCB will not come off without force as there is still glue underneath in the areas shown in attached picture. What I have found to be very useful is heat the chassis of the motor right below those areas with a soldering iron and then very gently pry off the PCB starting from those 2 areas. In some models, the glue in this area is very stuck and not heating the chassis beforehand will break the PCB. Even if you have broken the PCB, the traces are usually still intact. So take your time and remove the remaining part carefully and you will be able to put the motor back together.
Here are some images with motor used on WM-EX60/EX70/EX66/EX77/EX88/FX707. Motor is very similar to the ones depicted above, only differences being the case and fact rotor has only 1 magnet not 2. Unlike one shown in first post, the PCB is not glued on the case on this one, hence easier to disassemble. For easier removal of glue, heat the case with a soldering iron.
