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dpetk5
Beginner
121 Views

HDMI connected external 3rd monitor not detected when USB-C connected 1st monitor turned on

please see details in attached template. 3 external Dell P2419HC monitors. Monitors 1 and 2 work on USB-C. Monitor 3 is connected via HDMI due to bandwith limitations of USB-C. Monitor 3 will not be detected when USB-C monitors 1 and 2 are on; but will be if I turn off Monitor 1. This was working fine for a week. I disconnected my lap top to work remote. when I returned and plugged it back in, it stopped working as described. Please see attachment for more details.

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n_scott_pearson
Super User Retired Employee
97 Views

The Intel HD Graphics engines will only support 3 monitors simultaneously. From everything that I can see, you have 4 connected. Only 3 can work at any point in time. This is exactly what I expect and what you are seeing.

 

If you want the three external monitors to work, you must disable the laptop's built-in monitor. You need to make sure that this is happening (automatically) when you close the lid. I have seen cases there this did not always happen (and this was also with a Lenovo laptop).

 

I will also point out that if you are sticking to three standard 1080p@60Hz monitors, there is plenty of bandwidth in the DisplayPort channel that is embedded in the USB-C connector to support three daisy-chained (or MST Hub-based) monitors.

 

...S

dpetk5
Beginner
97 Views

The problem was the USB cable was in the wrong USB port. Once it was moved to the thunderbolt USB port it worked fine with the 3rd monitor on htmi
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