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

Thank you for the clarifications. I am going to spend the next two or three days studying this thread and others in the forum before I proceed. There is so much useful information, plus you and others are so knowledgeable and willing to share your knowledge. So I will absorb as much as I can and before I proceed.

 

Something that I want to add in regard to re-assemblying these coreless motors is they need to be adjusted after they're put back together.
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).

Also, it's very important to NOT push on the commutator when installing the rotor back. Rather, use a small socket and push the entire assembly while keeping the pulley still.

@Charles218 Please add any links from other sources in regard to coreless motors here, so all the information is in one place.

 

After studying this thread plus the thread here, I started back to work on my Walkman today. After unsoldering the FG and power wires I tried manually turning the motor. It was as though it was stuck but only needed a slight amount of pressure to get it to turn. With the motor now removed from the chassis I connected a battery and it now turns freely under power. Reinstalling the motor, then soldering all four wires, it now runs but only for 2 - 4 seconds then stops. This appears to match the diagnosis in the tread I mentioned above in this post. I will disassemble the motor tomorrow, checking to see if the FG connection is the issue, that is unless someone suspects that the problem could be someplace else.

A quick question, does the polarity of the two violet FG wires make a difference? When I unsoldered them from the board, I failed to note which went where.

 

The FG wires do not matter how are soldered. If you can, take additional pictures with the repair and post here.
The fact motor seemed like it was stuck suggests it may need lubrication which should be done anyway.

 

Yesterday I disassembled the motor, using the Living Analog video, plus the many helper notes in this thread, gave me the encouragement to move forward. I'm writing to ask a couple of questions before I proceed. This is my first time working on anything like this, and I am not 100% clear on the naming conventions for the various parts. I see names in this thread such as motor shaft, spindle shaft, hub, front motor bearing, copper tube, back bearing, and others. While these may be clear to those who are experienced, it would be very helpful if someone were willing to point out these parts by name on a photo. I've added a few names to the parts that I feel confident about, can someone point to others that I have left out?


Also, is there a best oil to use, or an oil to stay away from?

 

I edited the picture for clarity.
What is marked 4 is the shaft + pulley. The type that drives a belt is called pulley, a spindle looks different.
See picture attached with MNR-1602A motor used in DD walkman, which is essentially the same motor but with a spindle instead of a pulley and without an FG coil.
What is marked as 5 is the rotor. Being just coils, with no metal parts, it's what makes it a coreless motor.
The small copper contacts marked 2 is the commutator, which switches between coils. This exists on any DC brushed motor.
Below it there is a magnet that generates the varying magnetic field picked up by the FG coil (what is marked 1, the green coil).

The brushes are within the back assembly with FG coil.
Do note you will need to compress these brushes with a pair of tweezers before pushing the back cover back, so the brushes slide nicely over the commutator.

What was reffered as the copper tube is likely the combination of the 2 bearings (front and back). But from what I have seen there are 2 independent bushings, it's not a tube.

 

Perfect, this adds a great deal of clarity, Thank You!

Any advice on oil? What should I use or not use?

 

Watch oil is what you should use. You sould not use grease.
A pen type recipient like this https://www.ebay.com/itm/164185783921 is easy to use, but any watch oil is fine.

 

In reassembling the motor, I have a couple of questions. As was suggested in this thread, removing the motor shaft required considerably more pull than the video suggest. Now that I have reassembled all of the parts, I note that the motor shaft can be removed very easily. Is that the way it should be or am I missing something?

Staying with the motor shaft, in the video at about 2:15, he oils the front bearing and then appears to clean the motor shaft but does not oil it. Logic tells me to oil the motor shaft, or do I clean it and leave it dry?

 

If you move the pulley up and down, how much play do you have ?
It is not normal for the shaft to pull very easily after reassembly. There may some difference compared to first disassemble, but nothing huge.
Would want to make sure the rotor is pushed all the way in, hence my first question. If you pushed the rotor just 1mm for example, it's normal to come out much easier.

As for the video, please link it here.
Oiling the 2 bushings is enough, you don't need to soak everything in oil. It's recommended to clean the part of the shaft which goes into the rotor (after shaft is installed) for a tighther fit.
Of course you can add oil to the shaft as well, just make sure the overall amount is reasonable.

 

The only motor disassembly video that I have found is the "Living Analog" video that I found at the beginning of this thread, that is the one that I was referring to. I have cleaned the motor shaft, then applied one drop of oil, so I think I am okay there.

Moving the pulley up and down, I get maybe 1 mm, more or less, of play.

After reinserting the pulley/motor shaft, it will pull back out of the housing with the slightest use of force. I have searched without success for any special instruction on installing the motor shaft, but have come up empty. When I insert the motor shaft it stops about 3-4 mm before the pulley touches the front bearing. I can then slowly rotate the shaft until I find the spot where it will then push in the rest of the way, stopping at about 1 mm before the pulley touches the bearing, or it may be that the two small washers are touching the bearing. There have been a couple of occasions when I installed the shaft, rotated it by hand, and the FG end and wires also rotate, the same as at about 1:25 in the video. So I feel like something is wrong somewhere, I'm just not sure where.

 

It's way too much, you need to have 0.05-0.1mm of play. In other words there should be just enough play so there is no friction on the washers, nothing more.

In regard to install the motor shaft, will explain again how I do it:
- install the shaft in the motor case (after lubrication is done of course);
- add a small piece of paper between the pulley and top bushing to create that 0.1mm clearance;
- put the rotor inside and press it using a socket while keeping the pulley still against a surface;
You do need to put some force to get the rotor all the way in. You also need to press on the white part, not on the magnet or commutator as those won't take the force needed.

Given your description, I have the impression you may be doing the re-assembly steps in the wrong order. They need to be done in the following order:
1. Install the shaft in the motor housing together with corresponding washers. For the washers in the bottom to stay, just add some oil on them;
2. Install the rotor with motor sitting upside down (pulley facing down); Press on the rotor not on the pulley in order to install;
3. Install the back cover with brushes while compressing the brushes with a pair of tweezers;
4. Adjust back plate for minimum current consumption;

If at step 1 the shaft does not go all the way in you have either some scratches on the shaft or on the bushing. If so, some light sanding will solve the issue.

 

Valentin - I've been away from this project for the past several days with health issues, I'm now back and ready to continue, but I have two questions before I proceed.

For clarification, I've added a red arrow to the included image, is that the place where I add the small piece of paper to create the 0.1mm clearance?

Also, in step 3 - "Install the back cover with brushes while compressing the brushes with a pair of tweezers." In the other image that I am attaching, it would be helpful if you could indicate what the brushes are. Are they the six metal pieces that encircle the inner circumference of the housing? Or, are they the two metal pieces spanning the center of the opening deeper down? Either way, it is not clear to me how to compress them while installing the back cover.

Thanks again for your invaluable assistance!

 

Yes, that is correct.

In regard to re-installing the back cover, this part is where you should pay the most attention to. Bend the brushes and motor is gone. Brushes are what you marked as #2.
The brushes need to slide over the commutator, but given they're in the compressed position, the clearance between them is not high enough for the commutator to slide between them.
So you need to spread them apart ("compress" was not the best word to describe this) while pushing the cover down at the same time.
If the process doesn't go as expected, pull the cover back and start again, don't force it down.

Have attached a couple of generic images (not of coreless motors, but normal DC motors) showing how the brushes go over the commutator.
Pretty sure I have some close-up pictures of this particular motor somewhere, but unfortunately can't find them now.

 

Well, I have had several sessions trying to reinstall, but I am pulling my hair out trying to find someway to position the commutator between the brushes. In looking at the "Living Analog" video at the beginning of this thread, for a very brief second, I can see that the brushes have a gap between them when the commutator is removed. Unfortunately, that is not the case with mine, the brushes are literally right up against one another. I can easily create a gap using a toothpick to spread them apart, but as soon as I remove the toothpick, they spring back together.

I am trying so very hard not to damage the brushes, but I'm left scratching my head trying to figure this out. Is there a trick to spreading the brushes and having them remain open so that I can insert the commutator?

 

Are there holes on the back cover that are aligned with the brushes?
Sometimes I've seen a couple of tiny holes in the back where needles can be inserted to spread the brushes apart during installation.

 

Johny, in checking I do not see any openings, unless there might be something under the rubber grommet. It looks like the grommet could be easily removed, is that something that I would want to try?

 

I think so.

 

Unfortunately this type of motor has no holes to keep the brushes spreaded apart.
First, one has to remove that red plug in order to have access to the brushes from outside.
Then, use a pair of tweezers to spread apart the brushes while installing the cover. It's a bit tricky, but can be done.

Suggest to leave that black rubber part in place, it won't reveal anything.

 

I am still struggling to reassemble the motor, what seems so simple on the surface is turning into a real ordeal. Using Valentin's suggestion, I removed the red plug to gain access to the brushes, that worked beautifully, thank you. Looking through the opening where the red plug had been, I could see that the commutator was in position between the brushes, so I put everything back together.

The problem is the spindle can be removed with very little pressure, I don't think it could fall out, but it is certainly very easy to pull it out. I believe that I have followed Valentin's exactly, installed shaft in case, added an extra washer, (this instead of paper), put the rotor inside and pressed with a socket. Pushing with a socket does not really cause any movement, the spindle and the rotor appear to be in place without any pressure from the socket. I've use more force in pushing the rotor than I feel comfortable with and there is no movement whatsoever. I could push harder with the socket, but my instincts are telling me that something is going to break. Is there an "ah ha" moment that will tell me when the rotor is pushed in to the proper position?

I've attached a couple of photos showing my setup, the spindle has about 2MM of free play, I am aware that this is too much, so maybe I do need to exert more force on the rotor with the socket. I get a great deal of satisfaction in being a DIY'er, but maybe I've taken on too much with this project.