Thinkpad cursor drift

April 23, 2007 6:18 AM

The cursor of an IBM Thinkpad A20 is continuously "drifting". Do I need to get a new keyboard, or is there another way to fix this?

A few weeks ago the cursor on a Thinkpad A20 started "drifting", meaning the curser slowly moves toward the lower left of the screen without anyone touching the trackpoint "stick". In a given session, at first it drifts very slowly (a pixel every few seconds), then increasingly quickly, until after 10 minutes to half an hour it is drifting fast enough that it always hits the bottom of the screen with a couple of seconds of releasing the trackpoint. I upgraded to the latest trackpoint driver, but it's still happening, although it seems to me that the drift's accelleration is slower now.

Does anyone know if this might be fixable, either with software or by doing anything other than outright replacement to the hardware?

posted by jbotz to computers & internet (11 comments total)

The trackpoint is supposed to drift some -- always in the same direction. Let it drift to the edge of the screen and stick there, and it should stop. It is going to the edge of the screen to calibrate. The behavior you're describing often happens if you don't let it hit the edge of the screen, or if you're leaning on the trackpoint all the time.
posted by fake at 6:29 AM on April 23, 2007

The cover of your trackpoint may have moved and may be pushing the little stick underneath it. Try removing the red plastic nubbin and replacing it.
posted by GuyZero at 6:36 AM on April 23, 2007

I've seen this before, although it was on a Dell laptop, not IBM/Lenovo. I "fixed" it by reinstalling the pointing device drivers. Not sure why this worked exactly -- I assume it must have re-calibrated somehow.
posted by blue mustard at 6:37 AM on April 23, 2007

i have one Thinkpad 390 (win2k) that does the same thing. replaced the keyboard with no effect. Tried several OS's, with no effect. Sounds like a legit hardware error.

what OS? anything recently added?
posted by FauxScot at 7:11 AM on April 23, 2007

I once had an IBM service rep tell me that drifting was normal and this behaviour was within design spec.
posted by Nelson at 7:13 AM on April 23, 2007

My understanding of the anti-drift correction on Thinkpad trackpoints (and others, I guess -- my Dell D600's works the same way as my previous Thinkpad 570E and T23) is that it detects drift by looking for a constant reading from the trackpoint.

In fact, I can trigger the drift correction by holding the stick in one position very carefully -- the mouse eventually stops moving even though I'm still holding the stick, and releasing the stick makes the mouse move back the other way until it corrects the other way. And it never makes it near the edge of the screen -- it autocorrects in a few inches of mouse travel.

So "center" doesn't really matter -- what matters is "not moving". And it's at the hardware level, not driver, since it behaved the same way in Linux when the only driver I was using was "generic PS/2 mouse".

If your mouse is drifting and it's making it all the way to the edge of the screen, my guess is that the stick is still sending "moving" values rather than a constant value when your finger is off of it, so I'd replace the keyboard first.
posted by mendel at 7:35 AM on April 23, 2007 [1 favorite]

They all do that, sorry.
posted by caddis at 8:42 AM on April 23, 2007

Since you buy Thinkpads, I imagine that you use the trackpoint as your pointing device? Because if you don't, most mouse/trackpad/trackpoint drivers have the option to disable the trackpad/trackpoint (for people that only use the other input device)
posted by misterbrandt at 8:43 AM on April 23, 2007

I had a similar drifting issue with a Dell Inspiron 8000, though the drifting was more intense and I had to push the trackpoint very hard in order to gain control. In addition, the touchpad became pretty much useless. The issue was erratic and came and went per my laptop's desires.

That said, I fixed the problem by opening up the laptop, taking out the keyboard, and reconnecting the ribbon cabling that joins the tracking device to the motherboard. The plug had been jostled loose over time and was just sort of hanging. Attaching the cabling correctly cured the drifting.

May or may not be your issue.
posted by superfem at 10:11 AM on April 23, 2007

The trackpad driver will detect drift if you leave it alone for a few seconds. This is a known deal with Thinkpad nubbins going back to at least the mid-90s, and is inherent in the design of the hardware.
posted by zippy at 3:10 PM on April 23, 2007

My Dell Inspiron 8200 trackpoint's behaved that way almost from the beginning. Sometimes I can stop it by moving the cursor around using the touchpad, but that doesn't work every time, and I don't know if it'll help in your case.
posted by estherbester at 8:18 PM on April 23, 2007