Broken micromotors

[CP5670]

Do any of you know how to fix these things? I found this article on it, but I can't figure out how the open the motors (and have to run the article through a translator). Some old Lugnet posts I found suggested trying to move it manually while on power, but this is practically impossible since the motor is heavily geared down and there is no way to get a sufficiently strong grip using only the stud on the top. (I even used these, which have the strongest stud connections I could find)

Basically, the story is that a few years ago, I got a DOA micromotor out of an (unopened) 6483 Coastal Patrol set from ebay. It didn't move or make any sound at all. I used the Lego website replacement form and they sent me a replacement, but didn't ask me to return the broken one. The replacement worked great, but interestingly had some minor scuffs and looked used, and also seemed to run quite a bit faster than any of my existing ones.

Last week, I noticed that the replacement had somehow locked up in the same way. :'-( I don't know what happened to it, as it was working fine a month ago and had just been sitting in my spare parts area since then. I went through their replacement form again, but this time I just got a generic email that the item had been discontinued. So I've got two dead motors now and might as well try to do something with them.

I've read that these motors are prone to breaking like this, although I have a few others that work fine despite having been used for many more years. Any advice would be greatly appreciated. :-)

Edited March 7, 2008 by CP5670

[xenologer]

I have never owned a micromotor (sure wish i had one tho)

so I'm not qualified to give good advice on it...

But i have had a larger technic motor die on me once.

Upon opening it up i found that apparantly, one of the brushes had become misaligned and had been gradually wearing on the motor coils. Thus over time the conductivity thru them went down till finally the coil had been cut and it was dead. Irreperably so since those coils are made of fine wire that I cant replace or resolder.

Now that really sucks, so lets hope thats not your problem too.

Maybe you've got something simpler, like the coils are fine, but a brush has lost contact or something?

I'd probably just open it up, and look for anything obviously out of place, bent brush, scrape on a coil, worn out contact, etc.

[Brickadier General]

I've had the same problem. I bought an unopened Interstellar Starfighter from the U.F.O. series, and the micromoter wouldn't work at all. Like you, I asked Lego for a replacement, but the one they sent me didn't work at all either. So I just pretty much gave up on it after that. I'm thinking that maybe they've had a problem with a number of these motors being defective.

[CP5670]

Thanks for the replies.

But i have had a larger technic motor die on me once.

Upon opening it up i found that apparantly, one of the brushes had become misaligned and had been gradually wearing on the motor coils. Thus over time the conductivity thru them went down till finally the coil had been cut and it was dead. Irreperably so since those coils are made of fine wire that I cant replace or resolder.

Now that really sucks, so lets hope thats not your problem too.

Maybe you've got something simpler, like the coils are fine, but a brush has lost contact or something?

I'd probably just open it up, and look for anything obviously out of place, bent brush, scrape on a coil, worn out contact, etc.

I want to try to open the motors but can't figure out how to do it. The top has four small holes at the edges with what look like some sort of push pins inside. It seems like you should be able to push paper clips in them to pop them off, although they didn't seem to budge when I tried.

I think the problem may be something simple, since the second motor just died abruptly and wasn't exhibiting any slowdown or other strange behavior when I last used it. The electrical connection seems okay, since the motor heats up slightly if I leave it on power for 30 seconds or so.

I was actually going to use this thing in a space project as some kind of generator. I could probably get another one off Bricklink, but considering the price of these motors, it doesn't make sense to buy more if they're so prone to breaking.

I've had the same problem. I bought an unopened Interstellar Starfighter from the U.F.O. series, and the micromoter wouldn't work at all. Like you, I asked Lego for a replacement, but the one they sent me didn't work at all either. So I just pretty much gave up on it after that. I'm thinking that maybe they've had a problem with a number of these motors being defective.

Yeah, it's possible that a particular batch was bad. As I mentioned, the second motor I got ran noticeably faster and with a higher pitched sound than my other micromotors, many of which have gotten far more use but still work fine. The part number on the casing is also different. It may be a case of TLC replacing the internal motor with a different version (crappier in this case) but leaving the casing the same, which they also did with the gray Technic/Mindstorms motor.

[xenologer]

Have you tried jamming a putty knife into the seam between top/bottom and prying them apart?

Hopefully its not glue holding it together...

[Blakbird]

Philo writes about the micromotor here and took some motors apart here. It looks like you can't take them apart without destroying them.

When in doubt, bang on it with a hammer! :-D

Eric

[CP5670]

On closer examination, I think it's actually possible to push those four little pins in. They need to be pushed to the sides though, not inwards, so you have to jam something really thin into the holes and pry them in that way. It seems like it would require four hands to get them all in at the same time, but I might be able to do it with some effort. :-P I'll try it tomorrow when I have more time.

The two parts of the motor are connected very tightly and there is no place to get leverage with a knife or anything like that. They don't seem to be glued in any way though, as I can twist them very slightly.

I found another page on this motor, where you can see the four things I'm talking about. Although it looks like that guy screwed up his motor altogether.

[JINZONINGEN73]

If I'm not mistaken (and I could be!), electronic items like this are usually held together not JUST with tabs, but with a small amount of glue specifically designed for the type of plastic used.

Yeah, you might get lucky and get one who has so little glue that it pops off with some manual dexterity with the 4 pins, but more than likely there'll also be a glue bond at a point or two along the seam.

Applying too much glue at the factory might also be a cause of problems with a certain run of them (as well as too little).

Again, there may be no glue at all, but I've seen many a similar item assembled this way.

[CP5670]

BUMP

I noticed today that the micromotor in my 8480 has also died. It was working fine the last time I tried it, although that was several months ago.

I don't know if it's even worth replacing these given the rate they die at. The cheapest used ones are $15-$20 each on Bricklink. I wasn't able to figure out a way to open and fix them when I made this thread, but I might look into it again now.

I checked the part numbers on all my micromotors to see if there was a specific bad batch, but oddly, all 8 of mine have different markings on them.

[Jetro]

I was wondering about the possibility of taking those motors apart (for a completely different reason. Not all motors are glued together - I opened and fixed one of my 71427 Technic Motors without any problems.

If you have a broken micromotor, now is the time to try (and take some pictures!!) What's the worst that can happen?

[CP5670]

I have 3 broken ones in total now. But yes, I want to open and fix them if possible.

I don't think they are glued at all. There are some latches holding the two halves of the motor together. The site in the first post apparently decribes the problem, but not how the guy managed to open it. It would be good if one of the native Spanish speakers here could give a better translation of that site than Google.

According to the second site, the motor has a massive 2304:1 gear reduction inside. Trying to turn it manually would be hopeless, especially as it lacks an axle connector.

[Jetro]

Had completely overlooked the links!!

The Spanish site gives very little information and the google translation is pretty accurate.

[Zerobricks]

I just fixed one micro motor, by using parts of a broken one. The broken one had a fractured rotor coil, and i used its planetary gearing to fix the other one. The pin was too abused by its previous owner, for any lego to stick on, so i glued the appropriate pulley wheel on. It smells a bit when its working, but it turns!

Edited August 23, 2010 by Zblj

[CP5670]

Nice. How did you go about opening the outer shell of the motor?

[Zerobricks]

Using an alpha knfie, or how dio you call it.

[BachAddict]

The bottom casing is held on by ridges that grip a groove in the magnetic part. Unfortunately that part is glued into the top casing and you cannot get at the jammed gears from inside. This guy http://mindstorms.itgo.com/micro.htm opened the top by breaking off the ring around the output.

[DrJB]

I did open one. It was tricky, but once you do, it may be put back together by just snapping the parts, no glue there. The one I opened would not run because, there was a lot of magnet powder inside, and the rotor seized. The gear reduction mechanism is fascinating though. It resembles a planetary stage ... will need to take some pics and post them.

Edit: Looks like previous post has pics. Reason such motors seize is because 'something' rubs against the magnets and 'powderises' it. I was able to clean mine and reassemble it, works fine now. The trick is, how do you remove magnet powder from a magnet? The answer is simple if you have an old hard drive you're willing to sacrifice. The heads of the drive have a much stronger magnet than that in the lego motor, and of course, such magnet will pull the magnet powder/debris towards it, ie, away from the small magnet in the lego motor. One requirement for such job is ... Small tools, and small fingers. Happy micro-surgery ... But careful though, as the magnet ring is rather 'fragile'.

Edited February 13, 2014 by DrJB

[Technyk32231]

Philo writes about the micromotor here and took some motors apart here. It looks like you can't take them apart without destroying them.

When in doubt, bang on it with a hammer! :-D

Eric

That's the "minimotor", not the micromotor

[BachAddict]

I pried the back off, spun the rotor for a while and put it back together, and I think it turned a fraction before jamming again. I haven't managed to pull the rotor out of the magnet, does it come out easily? I will try some big magnets tomorrow.

For reference, can some people test their motors with an ohmmeter? Mine tested just over 100 Ohms, which is probably normal but I'd like to be sure.

[65sc02]

I had a case of "stuck 71427 motor". Disassembly worked fine with the instructions given here.

1. Removal of the outer cover is easy with a pocket knife.
   
2. Then I de-soldered the commutator plate and pried it off. Left-right-left-right and it comes off.
   
3. Now you have to remove the 4 locks in the corners of the casing. Just scrape them off with a small screw driver. Works fine!
   
4. Now you can push the motor out: push the black axle inside and the motor will come out on the back.
   
5. Use a thin screw driver and pry off the top metal ring. It is held in place only by magnetic force (strong!)
   
6. Now you want to remove the coil assembly. This is tough! I used a thick washer (4mm) with a big hole in the middle (to fit the PCB board through). And a vice to push the coil assembly out. This did not work all the way but loosened the glue. The last mm I did with a screw driver inserted between coils and magnet.
   
7. Using again a thin screw driver you can now remove the bottom metal plate with the magnet (very strong!)
   

I did not try to separate the magnet ring from the bottom metal plate. I don't know if this is possible at all (might be glued or just held in place by magnetic force).

In my case the cause of the failure was a broken magnet: its chromium outer seal had broken up and blocked the coil assembly. This may happen due to the motor falling down on the floor. Or due to humidity getting through to the magnet. This is, as far as I can see, a non-fixable failure: the magnet will always give off magnet dust particles which will block the coils.

Edited June 1, 2014 by 65sc02

[9v system]

I did open one. It was tricky, but once you do, it may be put back together by just snapping the parts, no glue there. The one I opened would not run because, there was a lot of magnet powder inside, and the rotor seized. The gear reduction mechanism is fascinating though. It resembles a planetary stage ... will need to take some pics and post them.

Edit: Looks like previous post has pics. Reason such motors seize is because 'something' rubs against the magnets and 'powderises' it. I was able to clean mine and reassemble it, works fine now. The trick is, how do you remove magnet powder from a magnet? The answer is simple if you have an old hard drive you're willing to sacrifice. The heads of the drive have a much stronger magnet than that in the lego motor, and of course, such magnet will pull the magnet powder/debris towards it, ie, away from the small magnet in the lego motor. One requirement for such job is ... Small tools, and small fingers. Happy micro-surgery ... But careful though, as the magnet ring is rather 'fragile'.

I had the same problem as well I put a flathead screw driver in between the join and pried it apart. then I cleaned out the powder and put it back together. the motor worked but only went one way then it died again because of a bent brush.

[9v system]

Going to try a net method of fixing these motors. I have ordered a broken one on brick link I will let you guys know if I can get some life back in this motor