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redblack
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Posts: 9
Registered: ‎03-26-2016
Location: RO
Views: 2,764
Message 1 of 15

T460 touchpad unresponsive when Ethernet cable plugged in

Hello,

 

I've bought a brand new T460 ThinkPad about 10 days ago, and I'm noticing that when I plug in an Ethernet cable, the touchpad becomes unresponsive: some clicks and taps are missed, movement is slow and and occasionally temporarily stuck. The touchpad comes to life again immediately once the Ethernet cable is unplugged. The trackpoint and trackpoint buttons above the touchpad are unaffected, only the touchpad starts to misbehave.

 

This happens both on Windows and Linux, so it's not an OS-specific issue. Moreover, I've checked to see if I'm running the latest BIOS version, and I am. And there are no issues when using the wireless adapter, but one of the reasons I've bought a ThinkPad was that it has an Ethernet port, so not being able to use it would be extremely dissapointing.

 

I've checked to see if there are IRQ conflicts for the touchpad, but could find none. The problem happens both when the computer is plugged in and when it's running on battery only. I've also tried two different cables in the same router, each in a different router port, and the problem persisted.

 

I am using the latest Windows 7 drivers directly from the Lenovo website, and Arch Linux with kernel 4.4.5 - the Ethernet adapter is seen as:

 

[ 2.751703] e1000e: Intel(R) PRO/1000 Network Driver - 3.2.6-k
[ 2.751705] e1000e: Copyright(c) 1999 - 2015 Intel Corporation.

 

Should I expect this to be fixed with a BIOS update or should I contact warranty? Living with it is unacceptable.

redblack
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Message 2 of 15

Re: T460 touchpad unresponsive when Ethernet cable plugged in

Tried an external USB mouse, it had no issues with Ethernet plugged in. So, the trackpoint works, an external USB mouse works, but the touchpad loses sensitivity and becomes choppy and occasionally unresponsive.

redblack
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Message 3 of 15

Re: T460 touchpad unresponsive when Ethernet cable plugged in

It would appear to be a grounding issue, because the touchpad begins to behave when I touch a metallic part of the laptop (the metallic part of an USB port, for example). I'm very dissapointed, I have cheap Inspirons that have never done this.

 

The charger, which does appear to be ground-capable, makes absolutely no difference - whether the charger is plugged in or not, the same thing happens.

dtscaps
Token Ring
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Registered: ‎10-28-2008
Location: Norway
Views: 2,711
Message 4 of 15

Re: T460 touchpad unresponsive when Ethernet cable plugged in

I'm not sure I can provide any answers here but this made me a bit curious. What switch do you have? Is it POE? Any HF transmitters in your vicinity? Have you tried a ferrite core on your ethernet cable / power cable?


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redblack
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Location: RO
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Message 5 of 15

Re: T460 touchpad unresponsive when Ethernet cable plugged in

I don't know what the switch is. My router is a classic WRT54GL. No, I didn't try shielding the cables with any device. No HF transmitters.

 

I do have two Dell Inspirons in the house that work perfectly. I've also used a Sony Vaio and a Dell Latitude laptop here with no issues whatsoever in the past. Later today I'll try this again in a different house (in another city, for that matter).

 

I am sure it's not an environment issue, there's a problem with the laptop. The only question for me now is whether to return the laptop altogether (not a great first impression for a T-series ThinkPad, and I'm still in the return window) or to have it repaired.

 

EDIT: If the switch before my router would have been POE, it shouldn't have made a difference anyway. This article states that "a PD indicates that it is standards-compliant by placing a 25 kΩ resistor between the powered pairs. If the PSE detects a resistance that is too high or too low (including a short circuit), no power is applied."

 

As much as I'd like to post-rationalize this and avoid a possibly frustrating experience in trying to fix or replace a laptop that I really wanted to like and waited for, this just should not happen in this price range, even if something in the environment wouldn't have been perfect.

dtscaps
Token Ring
Posts: 124
Registered: ‎10-28-2008
Location: Norway
Views: 2,677
Message 6 of 15

Re: T460 touchpad unresponsive when Ethernet cable plugged in

Like you said, it should'nt make a difference. I'm just curious. I also happen to work with radio stuff. I have seen the strangest things happen with RFI. Most likely you have a bad touchpad. I have a t460s here that does not have the symptoms you are describing.

redblack
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Message 7 of 15

Re: T460 touchpad unresponsive when Ethernet cable plugged in

Right, but this is a T460 (no 's'). Is that the same touchpad?

Skoop
Bit Torrent
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Message 8 of 15

Re: T460 touchpad unresponsive when Ethernet cable plugged in

"As much as I'd like to post-rationalize this and avoid a possibly frustrating experience in trying to fix or replace a laptop that I really wanted to like and waited for, this just should not happen in this price range, even if something in the environment wouldn't have been perfect."

 

You've answered your own question.  The onus isn't on you to fix what certainly appears to be a defect, from your description. 

 

Send it back.

redblack
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Message 9 of 15

Re: T460 touchpad unresponsive when Ethernet cable plugged in

Tried it in another house as promised, and the touchpad works fine with the Ethernet cable plugged in. Also, before leaving the house with the problem, I discovered that the problem occurs only when the cable coming from my ISP's switch is plugged into my router.

 

I do stand by my opinion that this machine deserves a more resilient touchpad, but apparently this is not the computer's fault - under normal circumstances there's no problem with the touchpad.

 

I'm stumped about how to proceed. I can use a multimeter on the cable coming from the ISP switch, but I'm not sure what to check (voltage? how much should it be and between what wires?). I'll also look into the ferrite core suggestion, I don't know where they are available - this thread is the first time of heard of them.

 

Anyway, just wanted to clear Lenovo's name on this one.

dtscaps
Token Ring
Posts: 124
Registered: ‎10-28-2008
Location: Norway
Views: 2,631
Message 10 of 15

Re: T460 touchpad unresponsive when Ethernet cable plugged in

I wouldnt care about plain voltages AC or DC. If your WRT54 is in a normal setup with nat/firewall I guess the only thing that may penetrate trafficwise is some kind of multicast traffic. So a wireshark trace to see if your ethernet adapter gets hit with a lot of traffic. You should also try to rule out RFI. Try looking at power cables on appliances in your house. you might find a ferrite core you can borrow.

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