WM-3/TPS-L2/WM-3 motor disassembly and maintenance

Repairing this motor is not simple, I would say one of the hardest ones out there. That's how it is with all coreless motors and these are used in a few walkmans other than SONY.

In regard to the pulley and play, that 2mm play suggests the shaft is not actually pressed into the rotor, but just sits on the top part of the hole. It really needs to go all the way in.
Then those washers: there are too many washers and not all of them go on the top. Some of them are on the top, some of the bottom.
As for the paper, adding more washers is not the solution, as that paper is supposed to be removed after the shaft was pressed not to remain in there.
To be mentioned you do not need to punch a paper to look like a washer, rather use a small rectangular piece which you insert between the pulley and housing or between any of the washers in there. Press, then remove the paper.
So, the number of washers need to be the same as it was originally. If you added extra washers, just remove them.

In regard to pressing the shaft, first of all examing the hole in the rotor and see if there is aby debris in there. If so, clean the hole before installing the shaft.
Then given the shaft has those vertical ridges, it will need a pretty significant amount of force to be pressed back in. A bit more than one would think.
Ideally, those ridges should align with the grooves already made into the plastic. If you can align them by feel, do so. But even without doing that, the shaft should go all the way in.

 

The four washers is what was on the shaft originally, I did not take note of which position they were in when I disassembled it. Actually, I did not see them at first because they are almost invisible. I will experiment with placement and remove the one extra that I added.


Thanks again for your assistance!

 

The very thin white washers I think 3 are on the top and 3 on the bottom. Then there are 2 thicker ones, one on top one on bottom.
Main idea is when you look at the interface between the pulley and bushing, you shouldn't see a stack of washers.
See the 2 attached pictures, on mine you can clearly see the 3 washers and another 3 which are put on top of another.
Also in your own previous picture, it looks the same: 2 of the washers are stuck together hence why it looks like there are only 2.

Note the DD motor in my picture also has a C clip near the spindle, the MNF1600B doesn't have that.

 

Well, I thought that I was there, made one more attempt getting the spindle installed and it work. The difference was using a socket as suggested, though this time I used a small tool and gave it a gentle tap and it snapped into place. Previously I was just trying to push the socket to lock the spindle in place, tapping it worked right away. Moving on to installing the brushes, all went well except now when testing it, before reassembling, the motor does not turn. I'm just using one of the batteries and making contact with the red and white wires. The spindle turns freely by hand, but no movement with the battery. I checked continuity from the red and white wires to the brushes and all looks good. Perhaps I've destroyed the motor. Please advise if there is anything else I can try, if not, I would look into purchasing a motor.

 

Do you get a resistance reading between the white and red wires ?
Try to rotate the back plate with brushes and see if in a different position the motor does start to turn.
Also while motor has voltage, try to rotate the pulley by hand and see if that starts the motor.

It's unlikely that you damaged anything, unless there was damage from before like open coils on the rotor or an open circuit between the commutator and coils.

 

Yeah, try turning it quickly by hand while applying voltage. One way or the other.
Measure the resistance of the motor leads by slowly turning the spindle one-eighth to one-quarter turn at a time.
There should be no interruptions in continuity or large changes in resistance.

I was wondering if it was possible to purchase a motor for this Walkmans.

 

Valentin, you have once again kept this project on track and moving forward, for this I am very grateful. I rotated the back plate and the motor sprang to life, all is looking good. So it appears that the last step is making the adjustment to the current consumption. In an earlier post you said "One needs to power them using a bench power supply (1.5V) or measure with a multimeter and observe the current consumption. Then rotate the back plate with brushes (while the motor is running) until the consumption gets to a minimum (it should be around 10-20mA)." It would be helpful if you could add a little more clarity to how I proceed with this step. I may have access to a power supply, and I do have a multi-meter, so far I have just been using a single AA battery when testing. It is not clear to me where to measure when I rotate the back plate.

Thanks!

 

Glad to hear you got to the last step !

For current measurement, you need to put the multimeter in series with the motor. See picture attached, load in this case is the motor itself.
Note you will need to move the positive lead of the multimeter to the mA jack for current measurement.
Given you use a AA battery as a power source, it would be useful to solder some wires to the battery terminals.

If you have an adjustable power supply with current reading, it would be easier to power the motor directly from the power supply and read the consumption there.
Depending on the supply you have, you may only have 2 digits after the decimal place, so you'll only be able to read in increments of 10mA. But it should be enough to do the adjustment.
Alternatively, you can put the multimeter in series with the power supply for more accuracy.