How to lubricate disc-type motor in SONY walkmans

Thank you Valentin, I appreciate you taking the time to listen. It is probably as good as it will get at this point so I’ll move on!

 

Hi Valentin,

I was under the impression that injecting watch oil through the plastic membrane on the other side of the motor would lubricate the shaft. Am I wrong? See attached pic.

That part of the motor is even made easily accessible from the outside without having to disassemble the Walkman. If not for lubrication, then what would be the purpose of making it easily accessible?

 

That plastic membrane is part of the bushing, it's there to keep the motor shaft at the correct height.
Don't know why on some motors it is made of transparent plastic, but it's not for oiling.
Piercing it to add oil will alter its geometry and also oil will tend to sip out through that hole.

Unfortunately there is no other way to oil the motor apart from disassembly.

 

Thank you! I successfully disassembled the motor of another unit (a Sony WM-600 Walkman) and lubricated it with watch oil, following your tutorial. I carefully removed the glue from the edges of the PCB using an X-Acto knife, which allowed the PCB to come off easily. When reassembling, I used tiny drops of PVA glue, which hold the PCB securely while remaining easy to remove in the future. It took a lot of patience, but it was worth it! A strong magnifying lens was invaluable in helping me avoid cutting the PCB traces.

 

Quick question here. I have two WM-10RVs that I am working on. I disassembled the motors from the top but upon re-assembly, they both make very faint scratching noises when I spin them and there seems to be more friction that before I lubed them. Is there a trick to re-assembly that I may be missing?

 

Noticed that faint scratching noise in WM-700 series motors myself, it's audible when the motor comes down to a halt.
When it's rotated as higher speed by hand, it's not noticeable. Not sure where it comes from, but seen it so many motors incline to believe it's normal.
What I'm reffering to is also not related to lubrication, this noise existed before/after.

As for the friction, it's normal to be a tiny bit more friction because of the oil's surface tension.
If after rotating the motor by hand it doesn't stop immdiately, it's fine.

 

Hi @Valentin

I'm trying to disassemble a (spare) WM-150 motor to see if I can potentially reduce the noise it makes when spinning, but I simply cannot figure out how I am supposed to remove the cover? There is no gap whatsoever that even a craft knife can penetrate around the edge:

 

@djsubtronic What you show here is not a brushless 3 phase disc motor, but a DC motor.
Opening it is completely different and more risky than the type I showed.
Wasn't aware WM-150 units also featured this type of motor. Do you happen to know the serial of the walkman it was installed on ?

To disassemble a brushed DC motor you first need to remove the pulley, then remove rotor + brushes as a complete assy (think back cover is part of that asstly) othewise brushes can be damaged.
Same goes for putting it back.
The back case is stamped in a couple of points. Generally I recommend against opening such motors.

 

@Valentin Thanks for the reply, I assumed these were brushless as well. I can't remember the serial number anymore as I have a lot of these motors that I already took out. Of all the WM-150s I have had, has either one of the below motors:



There are ones with thicker red+black wires soldered to the outside - I found these mostly on units from Japan/later units. Then there are the thinner red+blue wires that go into the housing. I found these mostly on UK/older units. The blue ones tend to run much quieter. I have yet to see a WM-150 (out of at least 11 or 12 units I have worked on) that has not had one of these two variant of motor. The WM-150 doesn't have a servo like the WM-2091 version for example.

 

Indeed all WM-150 use this type of motor. This particular unit is different than others using this mech.
I was so used to the WM-150 type mechanism using the brushless one that I thought all of them were the same.
On this recommend only oil the top bushing without disassemblying the motor.

These aren't brushless. You can tell by the shape of the back cover and housing and fact these only have 2 wires.
3 phase brushless have 4 wires: a B+, U, V, W (the 3 phases). Some can have more if the unit has separate windings for high speed FF/REW.

 

@Valentin have you ever encountered an issue with this DC type motor or have any ideas why it might enter a state where it fluctuates periodically between 2 different speeds? For example when calibrated to 3150 Hz, it will go between 3150 and 3080 Hz. This can happen every few mins, or every hour, and in both states the W&F is normal/good so there is no "noise" as such. Just two separate stable states. I have this issue with one of my motors and wondering what might cause it?

 

Seen this symptom in other walkmans using DC motors and it was caused by a dry bottom bearing.
Unfortunate part is in such designs there are only 3 approaches that can be used for lubing the bottom bearing:
- spray some oil through the part wires go in and hope it will get into the bearing. By far the easiest solution, but oil will get everywhere.
- drill a hole in the case where the bearing is (similar to how some already have a hole), but one has to be very careful because drilling in the wrong place can seize the rotor.
- actually open the motor and do everything from inside. The cleanest but by far hardest solution.

Not very familiar with this particular motor, but if they tend to have this problem one solution or another will have to be employed.

 

Thank you - if this problem persists I will try your solution of applying oil from the underside of the motor.

 

I just thought I would respond here in case it helps anyone else. I used a spare motor to see if I could get oil closer to the middle (where the bottom bearing would be) without putting into the wire hole and hoping for the best, so I attempted to remove the black sticker on the base. Turns out this is actually a rubber ring with a flat sticker on top. In the case of this spare, the rubber was accidentally broken in one section but I dont think this is consequential in any way. However, with a bit more care, the sticker alone can be peeled back to reveal the central part of the motor. Underneath, there are two holes near the very centre of the motor. I have a picture showing this, but the site is currently erroring when I try to attach so I can try attaching a pic later on. In any case, I applied small drop of oil in both the holes and then ran the motor for a while. I did this on Friday (4 days ago), rebuilt and recalibrated the device, and since then I have played the device for over 8-10 hours per day. The speed has been fully stable so far, so I think the oil hit where it was supposed to, and this is indeed the right solution to the stability issue I described above @Valentin.

One thing to note - this sticker + central holes only exist on the older style motor with blue+red cables, not the newer one with black+red cable.

 

That's very good news if the motor can be lubricated that way, even if it applies just to one specific generation.

Regarding the pictures, please re-size them to 2000 x 1600 pixels if they're larger, otherwise the forum won't accept them.

 

Thanks - it was actually only around 500x500, I think the forum had bugged out for a while. Here is the pic:

You can see two small openings, which is where I oiled.

 

Seen this design before, bearing can be lubricated through those holes.
Ideally the motor should be kept with holes up when oil is inserted so gravity naturally guides it into the bearing.
Bering itself is right it the middle, so the oil has to flow a couple of milimiters to get there.

The best motor design when it comes to lubrication are the ones that have the hole near the middle, although this design makes it doable too.