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    T420 LCD screen flickering when external monitor connected

    Discussion in 'Lenovo' started by kansei, Oct 9, 2011.

  1. kansei

    kansei Notebook Enthusiast

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    Hey everyone,

    I'm having a weird issue here with my T420 - I'm running it in discrete graphics only mode (Optimus disabled - just the NVS 4200m alone).

    Whenever I have an external monitor connected via the DisplayPort connection, the laptop's onboard LCD briefly flickers from time to time (especially when something changes the state of the graphics card, such as opening up the NVIDIA control panel and selecting the 3D graphics settings preview tab). It's actually not just a flicker - I see a set of vertical lines appear on the left half of the screen for a split-second.

    This only occurs on the onboard LCD - the external monitor looks just fine.

    Anyone else experiencing this? I've been trying all sorts of things - different external monitors, different DisplayPort-DVI adapters, different versions of the NVIDIA drivers, with no luck.

    My specs are:
    Windows 7 Professional x64
    Core i7-2620M
    NVIDIA Quadro NVS4200M
    8 GB RAM
    Intel 510 120GB SSD
    14.0" HD+ LED backlight Anti-Glare (1600 x 900)
     
    kansei, Oct 9, 2011
    #1
  2. lead_org

    lead_org Purveyor of Truth

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    what is the refresh rate of the internal LCD?
     
    lead_org, Oct 9, 2011
    #2
  3. kansei

    kansei Notebook Enthusiast

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    60 Hz - same configuration as when the external monitor is disconnected.
     
    kansei, Oct 9, 2011
    #3