Kensington Expert Mouse Trackball: Scroll Ring Troubles

Trackball Scroll Ring
Trackball Scroll Ring

The oddly named Kensington “Expert Mouse” (it’s a trackball) sits to the left of my keyboard, where it serves as my main pointer controller; I’m right-handed, but have used a left-hand mouse / trackball for years.

[Edit: a comment from the future compares it with a different trackball that may work on the right.

Also, search for Kensington scroll to find other posts. There may be no good fix for scroll ring problems.]

Recently the scroll ring has become balky, stuttering upward & downward rather than actually scrolling. It’s an optical device, so I suspected it had ingested a wad of fuzz that blocked the beam path.

The top photo shows the infra-red emitter adjacent to the scroll ring’s slotted rim. The silver bar to the right of the emitter is the magnet that provides those soft detents. There’s no obvious fuzz.

Disassembly is straightforward.

  • Tip the ball out into your hand and put it where it can’t possibly roll off the desk.
  • Peel the four rubber feet off the bottom, remove four screws, and the top half of the body pops off.
  • Remove three screws from each of the two button cap assemblies and pry the button caps off the case bottom.
  • Remove two screws from the ball socket, pull it off, and clean any fuzz from the openings.

Surprisingly, I didn’t find much crud at all.

Scroll Ring Emitter and Detector
Scroll Ring Emitter and Detector

This photo shows the IR emitter and detector, peering at each other across the electrical isolation gap in the circuit board. Nothing obviously wrong here, either…

They both seem to be dual elements, which makes sense for a quadrature position encoder. Unfortunately, replacing them seems to be really difficult; they don’t look like stock items.

So I put it back together, plugged the USB cable in, restarted the X server (this being Xubuntu 8.10), and it pretty much works again.

Kensington replaced a previous Expert Mouse under warranty when one of the three minuscule red bearing balls that support the trackball went walkaround, but that gadget had been getting erratic, too.

I’m not sure what’s going on, but I have a bad feeling about this.

[Update: More troubles lead to some interesting pix and an insight. Maybe even a fix!]

Further Update: Ten years in the future, a real fix appears!

59 thoughts on “Kensington Expert Mouse Trackball: Scroll Ring Troubles

  1. Thank you!!! My scroll wheel was not working due to fuzz. Very helpful

    1. Thanks for the take apart guide. I also didn’t have any visible fuzz/lint. Turned out that the IR transmitter was bent just slightly back from where it should have been. Works great now.

      1. bent just slightly back from where it should have been

        I wonder if what we’ve been seeing is a slight decrease in the LED’s IR output coupled with a slight misalignment: the output decrease is more-or-less normal, but the failures occur only in units with the most misalignment.

        Thanks for the victory report!

  2. I just purchased one of these and found the scroll ring doesn’t rotate very smoothly. Would you think it’s possible to apply some sort of lube in there without mucking up the electronics?

    1. It’s supposed to have smooth detents created by the magnet (the silver bar) against the perforations in the ring’s skirt.

      If it’s grinding or grating or rubbing, then open it up and extract the scroll ring. I added a touch of silicone lube with a toothpick to my older trackball, but it wasn’t obvious it did any good; the actual bearing surfaces are tucked away.

      Be really careful about slobbering lube in there, because it’ll attract fuzz like crazy!

  3. My scroll wheel has been grinding a lot, so I decided to pull it apart and in the process stumbled on this web site. Thanks for providing a clue about the tear-down. I pulled a bunch of gunk out, and attacked the innards with compressed air and isopropyl. As a bonus, I removed the little magnet that locks the scroll wheel into notches. Now it’s quiet and smoother. I’m not a fan of the ratcheting. Just pry away the plastic detent holding the magnet in via a hole in the center of the magnet and push it aside. Cheers!

    1. Glad I could help!

      Whenever I vacuum the floor under the desk, I pop the trackball out, hold the vacuum nozzle over the cavity, and run my finger around inside. That dislodges a remarkable amount of fuzz, so maybe the ring won’t accumulate a hairball.

      I learned the hard way not to stick the vacuum nozzle down into the cavity: those little red bearing balls are really hard to find in a bag full of floor fuzz!

  4. I had a problem with the scroll wheel working intermittently.
    The mouse has been dropped on the floor and I guess this may have moved the IR transmitter and/or receiver out of position.

    I cleaned them first but the problem remained so I moved them closer together and I works much better now.


    1. moved them closer together

      Given the low mass of the IR emitter & detector, I would not have believed they’d move, even under a shock load, but your experience certainly counts for more than my opinion!

      For what it’s worth, after switching to Arch Linux, the thing has worked perfectly. No stutter, no mysterious hangs, no peculiar behavior at all. Whatever was wrong came from the software stack, not from the hardware…

    2. I had much the same issue, I disassembled it, and after cleaning found that the black IR transmitter was “leaning” a little. I straightened it out, and now my “favoritest” mouse in the whole world works once again!!

      1. It seems those IR gizmos are woefully sensitive to alignment and prone to all manner of odd failures. Glad to hear you got it working!

  5. I bought a used Expert Mouse that had hardly been used but sat around for a couple of years. The scroll ring on it stuttered badly when I tried to scroll. I tried cleaning with compressed air first and that helped a bit. The IR emitter looked a bit bent so I straightened that and then the scroll wheel wouldn’t scroll at all (only stutter in place)! I moved the emitter very slightly closer together than it had originally been and now the scroll wheel works perfectly. Thanks for the help from the previous comments.

    1. I moved the emitter very slightly closer together

      That’s scary: the emitter should have enough mojo to bridge any gap. The fact that a millimeter or two makes the slightest difference must mean either the emitter or the detector is fading out.

      But it’s certainly easier than replacing the things and better than scrapping out the whole thing.

      Good work!

  6. Biggest issue I have is trying to align the piece of clear plastic covering the red sensor while attempting to reassemble the ball socket. Any tips or pictures to help place this bugger of a piece of plastic?

    1. I didn’t take the trackball cup off the base, so the lens remained in place.

      If the lens fits securely into the bottom of the trackball cup, perhaps you can squish some masking tape into the opening from the top to hold the lens in place. Flip the cup over, screw it down, then pull off the tape to reveal the lens.

      I’ve used modeling clay for that sort of thing. Clay would most likely leave an oily film on the lens, which couldn’t possibly be a Good Thing.

      Good luck… and report back on what worked!

  7. Thanks! My scroll ring was getting very unreliable. I followed your instruction (though I did not remove the button caps) and found lots of hairs in the scroll ring assembly. Cleaned it out and now the scroll ring works great.

    1. found lots of hairs

      Amazing what gets in there, isn’t it?

      Although my trackball was fairly clean that time, on other occasions I’ve opened a mouse or keyboard or some such and, if I hadn’t seen it with my own eyes, I wouldn’t believe I shed all that much hair & skin flakes & general crud… yick & similar remarks.

      Glad to hear you got it working!

  8. This helped me. I cleaned out the scroll ring and it works a lot better. Saved me from having to get another Expert Mouse or to try my luck with the Kensington SlimBlade, which has gotten mixed reviews – thanks.

    1. cleaned out the scroll ring and it works a lot better

      Some folks have observed that pushing the emitter and detector closer together helps, but I’d avoid doing that until all else fails: as long as it works, leave well enough alone.

      Good work!

      1. Well, the scroll ring has stopped working again.

        I have resorted to using MouseWorks to scroll up when the two upper buttons are pressed at the same time, and to scroll down when the two lower buttons are pressed at the same time.

        1. There’s definitely something wrong with that scroll ring’s design… I have a dead one just like yours.

          Thanks for the data point!

          1. For dead scroll rings, a useful alternative may be the “Scroll With Mouse” option that you can assign to one of the buttons using MouseWorks. Then if you click. the button, you can scroll by rolling the trackball. I am trying it out -seems ok.

  9. AWESOME! My mouse (er…trackball) purrs like the kitten of the cat hairs that were so deeply embedded inside it (for any of you considering this and saying ‘Naw, I clean out under the ball lots – it’s fine’ – Um, it’s probably not – especially if you own pets. The only thing I didn’t find in there was a small child…. Also, the tip about removing the magnet – this helps alot. I suppose it’s there to get “feedback” to the wheel but when the wheel stutters it’s just annoying – this keeps the feedback to the receptor moving smoothly too – and I think it helps. Also, quick tips: A pair of tweezers, each tong arm under the magnet (you’ll see the little slots where the magnet sits) is just the right lever to move the magnet up and past the little holder notch – use a small screwdriver to push this piece back a bit and then lever up with the tweezers and the magnet comes free without wrecking anything (in case you want to put it back). Also, when screwing the button holders back in place: Put each of the three screws in the holes in the housing and lower the holder into place then put about a 1/4 turn on each screw to hold them in place. This saves trying to get one screw into place, dropping it inside, fishing out, repeat, repeat, repeat… (banghead). Thanks again all!

    1. The only thing I didn’t find in there was a small child….

      But, if you had to, you could knit up a life-size doll from the fuzz!

      Thanks for the tips; I devoutly hope I never need them… [grin]

  10. Howdy again… one last bit – I put the child to bed, btw – since they’re small they don’t take up much room, lol… I find most of my scrolling is done on webpages and this is THE most frustrating then when the scroll wheel stutters – but check out this little plugin/extension developed by “Slice Factory” (I get nothing for this endorsement btw) – the “Magic Scroll for Safari” extension has two settings that work in tandem with one another – amplitude (how **much** of the page should scroll per a turn of the wheel) and duration – for how **long** will the page scroll after you spin your scroll wheel. What you get is a natural feeling FLOWING page that you can adjust – a tiny ‘flick’ and it slides up/down SMOOTHLY… a bigger ‘flick’ and it slides SMOOTHLY for LONGER. Basically it reduces the amount of finger work you have to do then because you adjust how much “english” to apply to the scroll wheel – same finger motion but different amounts lead you different distances up or down – this versus the ANNOYING creep, creep, creep, creep down the page of the current software from Kensington. I have a mac but Safari is available for windows too.


    1. Sounds like the right hammer for that job… for those of you with a Mac or Windows machine, of course. [grin]

  11. Sorry I have a question that I really appreciate if you can help. I just bought one of these Kensington Expert Trackballs (second handed) from eBay. Under the ball there is TWO red let’s say eyes! or something (sorry I don’t know the technical term) which are I guess for recognizing the movements. BUT I see actually THREE points for such red things. My question is that am I right about one of these red things missing or there is basically only two of them not three. Please kindly let me know about it.

    1. Those three tiny red balls are the bearings supporting the main trackball: with one missing, the ball won’t turn smoothly. You can use the trackball anyway, but you probably won’t like the feel as it gradually wears the missing support away.

      If you can’t buy a set of replacement balls from Kensington, you can pick up something similar on eBay. IIRC, the ones in my trackball are 2 mm diameter; measure the ones in yours to be sure. I think the originals are (artificial) sapphire, but ceramic balls will work just as well. I’m certain Kensington would have used cheap steel bearings if they could, so I’d avoid them.

      Good luck in the hunt… and let me know how it works out!

  12. Hello Ed,
    I really appreciate your quick response. I have two more questions:
    1- If you have Kensington Expert Mouse too then I guess they are all of the same size so my balls should be 2mm as well. I said this because measuring the exact size is kind of difficult for me since they are very tiny and actually glued in their place.

    2-So they are just to facilitate the movements. Right? I mean they have no responsibility to recognize the movements or in other words they are not connected to any other electrical pieces. Am I right?

    3- And the most important one, what is IIRC? I searched it in eBay but it didn’t give me any results. But when I search “ceramic balls” yea some results show up. So do you mean something like this:

    Thanks again

    1. On my trackballs those tiny bearing balls snap-fit into their holders, which are basically two ears with recesses. Perhaps the previous owner slobbered glue over them, but that’s not the way they started.

      The motion-sensing part is that glowing red cavity on the bottom, which is the lens for an optical chip much like the ones in optical mice. It peers at the flecks on the trackball, applies some magic, and reports position changes.

      IIRC = “If I recall correctly”

      I did pretty much the same eBay search you did and came up with much the same results. This gets more specific results: 2mm ceramic balls. I didn’t find anything interesting with 2mm sapphire balls, but perhaps that’s just because nobody’s selling them today.

      I don’t know that ceramic balls will be a suitable replacement, so I’d try getting original balls from Kensington first.

      1. Hi Ed, I have a Kensington Expert Mouse, the original cream colored one circa 1995 (ball and 4 buttons only). When I open it up, the encoder wheels that the ball sits on are only soldered to the board in 2 places at points CR4 and CR13. If I clip the wires that stick up from the board and remove the wheels (for an arcade project), and then solder wire to the board (3′ of telephone wire) and sensor in encoder, the encoder does not work. However, if I move the encoder wheel back into the board slot, it works. This is with my wires soldered to it and the original connections not touching (I am positive they are not touching). Is there some reason why the encoder wheels have to be on or very close to the board to work? Are they magnetic or is there some other principle in play? The voltage at the board and at the sensor after my length of wires is still 1.22V. I’m at a loss, and tremedously curious at this point, even if there is no solution to using the encoders without touching the board. Thanks in advance for any replies, even ones that point me to other places to do additional research.

        1. Is there some reason why the encoder wheels have to be on or very close to the board to work?

          They’ve gone to an optical encoder since then, so I don’t have any direct experience with the wheel encoders. The 1.2 V suggests a forward-biased IR LED, so perhaps they’re shining an LED through a grid wheel onto detectors on the board. Or the other way around?

          I’d use an oscilloscope to discover which wire carries the signal, then trace it from there. That ought to be good for at least an evening of Quality Shop Time!

          Good hunting…

    2. Just a quick update, I contacted them and they said those bearings can not be sold separately but in my case they were kind enough to send me a new trackball (I guess because the defective one has got like 5 years guarantee or something? I don’t know) but anyways I’m still using that defective trackball too and I need to admire that the sense is not good especially in some directions because of being short that one red ball….but the new one is awesome except sometimes that the left click is not very sharp! I’m using it in windows 7. Sometimes like I need to press it hard or a couple of times for the left click to affect (for me it’s not a big deal though because I have my keyboard mouse enabled at the same time…)
      I’m still looking for a tiny ball to fix it though…

      1. they said those bearings can not be sold separately

        Huh. It’s an easily lost and absolutely vital part without which the whole thing won’t work. Wonder why they wouldn’t want to make that available?

        I’m still looking for a tiny ball to fix it though…

        A while ago I was looking for something else and found 2 mm ceramic balls on eBay. They’re not sapphire (or whatever), but they ought to be just about right for the job. Who knows? Maybe you can get sapphire balls every now and again?

        You should measure the balls, just to make sure those haven’t changed over the years… like everything else!

  13. Thanks for the article and comments. I did a compressed air cleaning first, but that didn’t work – then I moved the outer (white) sensor in towards the wheel. I went too far the first time and it stopped working completely, but then I went back about halfway and it was as good as new again. Thanks!

    1. went back about halfway and it was as good as new

      Those things must have a beam about a micron wide: the slightest misalignment kills the scroll ring stone cold dead.

      Thanks for the update!

  14. Yes, I’d say so – in the end, it probably only moved the width of a staple or paperclip – but that has made all the difference!

  15. I cleaned the crud out first, which didn’t solve it. However, after bending both emitter and detector, and it all works wonderfully again. Thank you for the effort of putting the page together.

    1. If I didn’t know better, I’d say gremlins were flitting around the world, putting crud in all our trackballs and bending the IR machinery, just enough to drive us mad!

      Glad to hear it’s running again…

  16. I have just used the Task Manager to check the amount of CPU required to run the scroll wheel.
    It was between 30% and 60% !! (Set the update speed to High in the Task Manager “View” menu)

    If it needs this much attention it may be stopped from working for a while by other background processes that have higher Interrupt priority.

    Can the interrupt priority be changed?

    1. It was between 30% and 60% !!

      If that’s while you’re scrolling, most likely it’s due to the video driver shuffling all those bits across the screen. I’m sure that depends on the video hardware and how well the driver manages the operation; if the CPU must render those new bits appearing on the screen, then there’s no way around high CPU usage.

  17. thanks for this post!! I had an old one of these laying around that was at one point dowsed in water a couple of years ago, the scroll wheel had not worked since. I cracked this sucker open and fiddled with the black IR receiver like many others have, and got it to work. So happy to have the mouse of my dreams back!

    1. the mouse of my dreams

      We are rather enthusiastic, aren’t we? [grin]

      Glad to hear it’s working again… may it continue to behave for you!

  18. I turned off smooth scrolling and the scroll ring stopped giving any problems.
    I had always suspected a software problem but was looking for conflicts and not thinking of a “settings” problem.


    1. Ah! Software seems even less tractable than fuzzballiness in the optical path…

  19. This is fantastic info – thank you for posting the detailed trackball disassembly instructions! I just finished cleaning my Expert Mouse (yeah, goofy name for a trackball) a few minutes ago with GREAT success. I did indeed have a hairball that was fouling my scroll ring’s function. Cleaned out the clog & other miscellaneous hairs/dirt, took the suggestion to remove the magnet because I never cared for the ratcheting either (thank you, Tom Levesque), and while the ring assembly was out, added a small amount of dry gun lube (Tuf Glide) to the 5 points on the underside where the plastic ring meets the metal – now it’s smooth, quiet, and again completely functional!

    1. And, with any luck, it’ll last another few years before that IR pair goes crazy…

      Good work!

    1. The small magnet inside produces the soft detents as you turn the scroll ring; removing the magnet will eliminate the detents.

      Unfortunately, the ring doesn’t rotate on actual mechanical bearings, so the metal-on-plastic motion will always feel gritty. I don’t know of any way to fix that, alas.

      If you mean smooth scrolling inside a Mac application, you’re on your own… [grin]

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