Weird tale: Touchpad/Trackpad

[Bill]

I don't feel like testing the patience yet again of the UK homebuilt ng by serial OTness, so I'll inflict this here.

I've got a really nice Lenovo X201 laptop from ebay that I would like to make my main machine. It's not long out of warranty and looks almost new. It has a touchpad and the usual Lenovo Trackpoint.

The Trackpoint works fine at all times. The touchpad works fine for the first few minutes or more. Then I continue to use my 2nd finger right hand, but the cursor responds in a progressively more jerky and annoying way. I switch to my 3rd finger and the cursor response is fine for quite a while, but eventually it develops a similar trait. I then switch to the left hand and the touchpad is fine again.

After a bit I can revert to my right hand and that seems to have recovered for a short time.

I have applied the fingers to pads on other laptops and they all work fine.

Licking a finger seems to help a bit, but not a lot. Connections inside all look fine and when the pad works, it responds smoothly everywhere.

I believe that the touchpad is made by Synaptic and uses a matrix grid beneath the pad with a signal, perhaps of 200 to 300kHz to provide the capacitive sensing. I've used a medium wave radio to compare 2 pen-tablet laptop screen matrices, where the frequency is higher. I don't have a small LW radio, and it probably wouldn't show anything up.

I'm not sure whether it's likely to be the pad, the signals fed to it or some problem with my fingers. Is anyone here an expert on this?

[Tim+]

No idea. I'd plug a mouse in. ;-)

Just a thought though, you're not unconsciously touching the pad with another part of your hand after a while? An errant pinkie getting too close perhaps?

Tim

[Bill]

In message , Tim+ writes

These are small, like laptops used to be. A mouse isn't really small enough to be handy, especially for holding the machine and walking around.

I've just checked and there is no errant body part or item of clothing dangling in there. The pad, like the machine, is pretty small. Good question, though.

[Lee]

Are you using the correct driver, is the pad surface clean and free of residue and does this happen both plugged into the AC adapter and on battery?

[Bill]

In message , Lee writes

I'm using the one from the Lenovo support site for this machine (you select quite a detailed part number). The machine has the original recovery partition and had been reloaded from that. I will check again, but I have checked and reloaded a fresh copy of the driver. Device Manager says it is working correctly.

Yes. I haven't tried any alcohol yet, but I have scrubbed it with the sealed lens cleaner pads sold in supermarkets. These seem to clean screens OK and don't seem to leave any residue. The machine was very clean when I first got it. Now there's just the usual hair falling out and getting stuck under the keys.

Yes, I've tried that.

[GMM]

I've had erratic trackpad operation and found it coincides with using my right hand while my left hand is resting on the body of the laptop (not the trackpad, just the body). Doesn't happen all the time but I suspect the right combination of humidity (or summat) means my left hand is upsetting the way the pad works.

[Brian Gaff]

I had one of these on a Dell, and that one was affected by my breath, it just jumped about. I now end up turning off these blasted things in the control panel.

Of course, for me they are a menace, but I fully understand that sighted folk need them to work, so the only thoughts I have is to do more testing. IE don't swap fingers when it happens, get an inanimate object and poke it a few times and see if the original finger then makes it work. What you also need to perhaps look at is any kind of polish or cleaner around the place or flexing of the case near it. Hopefully you do not have the problem I read about some time ago, where the pet cat tended to go to sleep on the open laptop when nobody was around and it had gone into standby. Brian

[John Williamson]

I occasionally got the same, and it seemed to be caused by the finger drying out with the friction on the pad. "Huffing" on the finger worked for a few minutes, so I turned up the pad touch sensitivity in the driver. Problem solved. Don't go too far, though, as if you have "Tap to click" enabled, you'll start getting phantom clicks instead.

[polygonum]

Well, expert with ONE resolved issue under my belt. :-)

That was a MacBook (the old white one, something like seven years old?). The touchpad started to misbehave. Eventually realised that the battery lies immediately under the touchpad. That had become swollen and was applying pressure to the underside of the touchpad. Realised the if you took the battery out and ran mains only, all was well. Replace battery and it misbehaved. Others have reported similarly.

[Lee]

Must be you then! Are you by any chance acting as an antenna for a strong local RF source?

I did have one netbook that had an erratic pad whenever BT was enabled, but I always assumed that one was broken.

[Graham.]

The touch screen on my satnav is rendered unusable under certain conditions. seems to be when the sun heats it ununiformly, but I'm not

100% sure why it happens.

[John Rumm]

Perhaps you should try it with one of those soft ended styli designed for touch screen use. Failing that, try some moisturiser!

[Bill]

Thanks, John (and everyone else). I think it is sorted.

After the torrential rain yesterday, it was a lot better but then this morning, even though there was still rain, it seemed to be starting to happen again.

I had previously thought I had gone through all the touchpad settings, but none of them seemed to help. Adjusting the sensitivity (which has a note saying it might be necessary in humid conditions) on its own made no difference. There is a setting called "Palmcheck", which I had missed. Adjusting this in conjunction with the sensitivity seems to have cured the problem. I've now tested for most of the morning.

Because the touchpad is recessed, unlike most current machines, I can't see there being a problem from accidental grazes of the pad while typing, so, if it keeps working, it's a win-win situation.