Fixing A Complicated Scrollwheel

[Thomas] loves his Logitech MX Master mouse, which has a pretty elaborate scroll-wheel mechanism. Perhaps too elaborate; it broke on him after a week of use, just when he was getting used to the feature. So what did he do? Took it apart and fixed it, naturally. And as a bonus, we get a guided tour of the interesting mechanism. Check out his video below to watch it in action.

The weighted scroll wheel switches between two different modes, one with a detent like you’re probably used to, and one where the wheel is allowed to spin freely for long-distance travel. And to do this, it’s actually got a little motor inside that rotates a cam and throws a lever into the side of the scroll wheel for the detent mode, and pulls the lever out of the way for free spins. It must also have some logic inside that detects how quickly the scroller is spun because it re-engages as soon as the scroll wheel stops.

It’s a sweet mechanism. But it has one flaw. The cam can work its way up, where it misses a stop and over-rotates, leaving the scroll wheel in a half-detent, half-spinning no-man’s-land. Simply pushing it back down seems to fix it, at least for a while.

We love fixes. And we love peering inside machines with cool mechanisms. So thanks, [Thomas] for opening up your mouse with the camera running.

51 thoughts on “Fixing A Complicated Scrollwheel

      1. +1.
        -Bought a Logitech MX performance, middle click is awful, you have to press it while holding your hand in a claw like position. If you don’t press it a precise angle, it does nothing. Battery life is really bad, about 1 week(max). Love the scroll wheel though, with the fast scrolling feature.
        -Bought Logitech G602. Very good battery life, and you can actually use it for middle clicking without holding your hand in an unhuman position. No fast scrolling though. After 3-4 months it broke, the middle click microswitch was no longer working. They used high quality switches (OMRON) for everything except the middle click. A week later I buy another Logitech G602, after 1 month the middle click is no longer working.

        1. Strange, I’ve got Logitech mice from a few different lines and never experienced button failure. I’ve used the one on this machine for 4 years now and it’s the lower end line M310. The plastic has structural cracks developing on the towards the back of the mouse, but the buttons and scroll still work great. I have an M570 ball mouse at home, and that works a treat after 2 years of constant use still. I game a decent amount, and board dev, so it’s not like I’m not running these through the ringer.

          1. Maybe I’m really unlucky, I had major problems with all my 3 Logitech mice. I use mine mostly for HW design and some gaming and they seem to fail when I need them the most.
            Google-ing G602 middle click returns a lot of results including an instructables how to fix your middle click button.
            But hey, what can you expect from a company that sells a “500W RMS” surround system and if ask them for the mains power consumption after a 20 e-mail exchange they will say that that they don’t have this data available. (funny thing, the power rating is printed on the back of the device).

          2. My next mouse would still be a Logitech.
            I have had 3 primary mice over the past 16 years… All Logitech, and the only real problem I have experienced is the scroll problem on the MX Master…
            I got the MX Master free of charge because the right-button on my 2 years and 11 months old MX Performance started to behave a little strange.
            However, I used the MX Performance at least 12 hours a day (work & home) and I could have treated it better (bad temper), so I’m just amazed that it survived for so long. Battery life is still 1 week, which is fine for me (I dock my mouse 2 nights per week).

            I have a whole drawer of mice from other brands, however none of them are an ergonomic match.

          3. Got an MX1000 Laser I bought like almost 10 years ago, and it still works like a treat. Battery is going low faster ofc, but still gets enough runtime for me

          1. I’m a bit cynical too, but in this case I have to say that I heard many people tell that if you have an issue they are very easy about sending you a new mouse at no cost.

            Doesn’t distract from this kind of poor attention to details, like with the mouse of the article, it just needs a better fix of the plastic part on the motor (or servo) so that it doesn’t slip off, seems something a proper engineer would have had working before it was shipped.
            And they had more sloppy issues with various mice. But to be fair, other manufacturers also have such issues, microsoft for instance, their mice are fine except that the cable gets slowly internally damaged where it enters the body, and then it starts to give intermittent issues until you cut the bit out and re-attach it leaving you with a working mouse that has a cable that’s an inch shorter.

  1. seems like the detent could have been done magnetically? say a pattern of magnets in the wheel, and then electromagnet in the mouse, the electromagnet is either connected (detent) or disconnected (free spin) to a resistor…

    1. Hey, why don’t we replace the Omron microswitches with those piezo generators that create the spark in lighters! You’d surely generate appreciable amounts of energy, and who cares about sore fingers after only three clicks anyway – we can make it “green” and “sustainable”…!

  2. Looks like the cam needs a bit of loctite on the shaft, or their overall design should have included a guard to stop it from climbing. Nice job figuring out the issue though.

    1. this! or even a bit of superglue. Can the cam be pulled off w/o damage? (probably, since it’s already off) but I wonder about how it figures out the orientation/clocking of the cam. I’m actually surprised it’s as easy as just pushing down the loose cam bit… maybe the mouse figures it out?

  3. I have the original MX Revolution, with an extra thumb wheel that I have configured for Ctrl-V, Ctrl-X, Ctrl-C.
    It is the best invention since sliced bread! …and of course Logitech removed it in newer models…
    What’s wrong with those guys…?

    1. Yeah. The MX Revolution is the best mouse I’ve used. When I noticed that Logitech were discontinuing it, I bought a couple spares. I’ve never had problems with the scroll wheel though and I’ve been using it regularly for years now. I guess the newer models aren’t as well designed going by complaints here and on reviews.

  4. Love my logitech mx705. I has the same feature where you can use the wheel in weighted free-wheeling mode or detent mode.

    I guess its more reliable because you switch modes via a clicky mechanical switch. (like a pen). Has lasted over a year with no problems so far.

  5. the last 3 logitech i got broke in a week. one left button , 2 scrolls. Their stuff really is crap lately. The last thing i got that was good was my speakers and they havent been sold for years.

    1. indeed, the quality has suffered a lot at logitech.
      my story started with the good old MX revolution. one of the best mice i ever had. the scrollwheel was awesome. the automatic switching between free running and regular mode was the best feature. but after 2 years the left mouse button failed. it either did not click at all or make doubleclicks when i just pressed it once.
      it still had warranty so i got an mx 1000 as a replacement because the revolution was no longer available. the mx 1000 was ok, but suffered the exact same problem after a shorttime.
      then i got the performance mx. it does not have the thumb wheel but i didn’t needed that anyway. the wheel is the same as in the revolution, except for the automatic mode switching. it is now manual. not as good as auto mode but ok. they never used the automatic switching ever again after the mx revolution.
      however my first performance mx died also from the same reason as the others. left mouse button problem.
      but thanks to the warranty i got a new one. if i had not i might have bougt the mx master.

      why i keep buying logitech ? because they still make the best mice in my opinion. i work and play with my pc.
      great for office and work and good for gaming.
      also i can’t live without the free running and weighted mouse wheel. ever again.
      never seen something similar with other mice.

      their support is also aweful.
      when the 2 mice that still had warranty broke, i tried to get support from logitech.
      their website was broken for over a year. unable to register an account or login.
      no phone number. i found a phone number only on the facebook page of logitech.
      they told me they knew that the site was broken. for warranty i should contact the dealer.
      luckily i bought at amazon. the mice have 3 year warranty. after 2 years the dealer is not responsible anymore here in germany. but amazon was nice and replaced my mice in the third year because logitech did not give a crap about customer support.

      1. just for comparision, i still have some older logitech mice that are over 10 years old and still work perfectly fine.
        among them my trusted logitech dual optical mouse from 2001. still in use and still good and working. i used that mouse as my main input device longer than all the MX mice together.

        1. I came across an old joystick many years ago, something like, sidewinder force feedback pro, or similar. That thing had two film canister sized motors inside, loads of torque, that variably fought back against you’re movements depending on the in game forces.
          That was a reasonable application that could use a couple of motors, a mouse, not so much.

          1. I disagree.

            Smartshift (the motor) is the best feature ever and even though I bought a G700S now and like having the extra buttons, I still miss that feature from my old MX Revolution.

            I wish Logitech could get it together and make a G700S with smartshift and better battery life. I would buy that in a second, even if it was $500.

            There are heaps of options if you don’t want smartshift.

      2. Yeah man I spent a few months buying , breaking, returning, replacing mice. I kept getting the warranty and everything with it so the store knew I was serious. I finally asked the manager and explained i use my pc like all the time and ended up getting a razer mamba . Its the best mouse since the microsoft intellimouse which I still would pay to have back in its original form. The first razer died after something like 3 months to a year I honestly forget. I had a bit of a hassle getting service as both razer and the store didnt know which warranty to file under. In the end they sent me 2 new mouses. I was happy for a year . A button broke. I disassembled the mouse and did surgery and fixed it. About due for another tune up now come to think of it . It doesnt always register button up. Overall a decent mouse. It cost like 200$ :/

      3. Another Detail, the performance mx has a single AA NiMh cell (eneloop) which can easily be replaced on the bottom side. The mx Master has a build-in Lithium battery. Non meant for replacement.

      1. I think most here are like that. There’s always a microscrewdriver kit nearby, and some products have arrows pointing where to put it! They want us to void the warranty, I’m sure of it.
        (Some companies don’t and think a sticker is going to stop me; they’re wrong.)
        Somebody has to appreciate their hard work, might as well be us!

  6. Sadly this is so typical of Logitech.
    They pay a lot of attention to the “look and feel” of their products, but slack off on the reliability and durability aspects.

    1. To this day they can’t seem to put durable potentiometers in anything. I’ve had this problem with the original Wingman Rumblepad, the later cordless model, and the pedals on my G27 wheel.

  7. Who the heck thought it was a good idea to put a motorized anything in a mouse, let alone to drive a mechanism that could easily be operated manually by the user? I have an M500 (corded, 4 buttons) that I absolutely love that moves the mechanism with a push-on push-off direct linkage. I’ve used it for at least 5 hard years with no signs of giving up. As a manufacturing electrical engineer I am baffled why you would invest the extra cost per unit into a motor with a much shorter lifetime than a manual button to drive such a simple function. Is it because this is a luxury product?

    1. It is automatically adaptive, not something a manual button is good for. It goes from detent mode to free-wheel without the user doing anything but roll the wheel. There’s no reason this has a short life that can be related to the function; it’s an implementation problem – either design or manufacturing.

  8. I highly recommend these new mice with a weighted, free spinning middle mouse button. They are superb in every way. Other brands that also have these free spinning middle wheels are likely to also be very good for most users.

    While I dont doubt they break, I have two of these MX series mice, one of which has lasted 3+ years of extreme abuse, the other pushing a year, and neither has had any trouble.

    1. Aaaaand, it turns out n either of mine have this motorized version of the detent cam.

      Why TF would they put a friggin motor on it!?

      They must want it to fail…..

  9. I’ve been using a logitech M-BJ58 every day since it was purchased new in 2000 or so. The right mouse button recently started to miss some clicks, after moving house 9 times and out-lasting at least 5 workstations. I love this mouse.

  10. I’m still using a Logitech MX 518 that I bought back….. um, a good few years ago, and then only because it was more interesting cosmetically than the MX 510 that was still going strong.

    I’ve also snagged a few 518s at Goodwill for a buck or two and given them to friends who were looking for a decent mouse.

    As others said, the current quality may be lousy, but older Logitech gear is pretty solid.

  11. Odd, I have 3 of them all over 1 year old which have been dropped several times from about 3 feet and they’re all working fine. I did have to have a dongle replaced once but that has been the only problem for me.

  12. And that is why i prefer easy solution with turbo button. Normal scroll wheel but when you press button and scroll (1 click is enough) it will kee scrolling fast until you release button. If i remember corectly, that was solution on some Genius mouses.

  13. I had the same problem, returned the mouse to Logitech after 5 days. Replacement mouse is ok so far but probably won’t last long. At least it’s good to know it can be fixed.

  14. Thank you so much for this fix. It worked perfectly. I really like this mouse and did not want to give up on it. Regrettably, Logitech has remained silent about this defect despite many complaints on its user forum.

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