UD-3900PDZ docking station, HDMI-1 Alt mode not working


I just received my UD-3900 PDZ, all plugged and powered. HDMI-2 &3 are working fine but HDMI-1 will not work. I have updated the displaylink drivers but this has had no effect. can you assist ?


Hi Jamie,

Thank you for contacting us, I am sorry this is not working as expected and I am happy to help!

The UD-3900PDZ USB-C Triple HDMI Docking Station’s HDMI 1 output port relies on USB-C DisplayPort Alternate Mode, or “Alt-Mode” for short, this is an optional USB-C feature that is not supported on all computers or by all USB-C cables.

Our first step is to make sure the docking station is connected to the computer using a compatible USB-C data cable that supports Alt-Mode video. Please connect the docking station directly to the computer’s USB-C port using the USB-C cable provided with the UD-3900PDZ docking station. USB-C “charging” cables or cables from other devices may not support Alt-Mode video, additionally adapters, hubs, and cable extensions may not support Alt-Mode video. Please let me know if this enables the HDMI 1 output port.

If not our next step is to check to verify that the computer supports USB-C DisplayPort Alternate Mode, for computers running Windows:

  1. Open the Start Menu and search for “msinfo32” and launch the first search result
  2. Please let me know the values from the following entries ( on the right column ):
  3. “System Model”
  4. “System SKU”
  5. Please feel free to attach a screenshot of this window to your reply if you prefer by using the Windows Snipping Tool ( from the Start Menu search for “Snipping” ) and I can get the details from there

If this is an Apple computer:

  1. Open the Apple Menu > About this Mac
  2. Let me know the model name and year ( for example: MacBook Pro 13-inch 2017 )
  3. Please also let me know if this a new Apple M1 system, or if it uses an Intel processor
  4. Please feel free to attach a screenshot of this window to your reply, using the Apple shortcut keys: “Command” + “Shift” + “4” + “Space bar” then clicking on the window to take a screenshot that will be saved to the desktop.

Thank you for these additional details, I look forward to your reply.

Plugable Technologies

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