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Can't connect external display to MacBook Pro

Hello Community and Support,


Hello,


I have a MacBook Pro (15-inch, 2017). I bought a NEC EA271U monitor. The MacBook is connected to the monitor using a USB-C - USB-C cable (USB standard 3.1 Gen 2).


Unfortunately, I have a problem with the correct connection of the above set. The monitor does not see the signal on USB-C input and macOS Catalina (10.15.6) does not recognize the monitor. Only Power Delivery from the monitor is available.


The monitor on the same cable works correctly with a Lenovo notebook with Windows 10 OS (both image and Power Delivery is available). A MacBook Pro on the same cable works correctly with another monitor that supports USB-C (both image and Power Delivery is available).


I have already reset PRAM, NVRAM and SMC - that does not help.


Any suggestions why NEC EA271U monitor and MacBook Pro could not work together, and how to fix that?

MacBook Pro 15″, macOS 10.15

Posted on Aug 20, 2020 10:44 AM

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Question marked as Top-ranking reply

Posted on Aug 21, 2020 1:20 PM

Look at:


 menu > about this Mac > (system report) > Graphics & Displays


When your display is recognized (i.e., answers back over EDID), it will show up there with its name and capabilities, even if somehow it got set to a resolution out-if-range.

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11 replies

Aug 20, 2020 12:18 PM in response to a brody

HDMI was invented for HD TV sets. It is comparatively difficult to get the appropriate HDMI cabling for displays over HD (1920 by 1080), and it often involves quite a bit of black magic to get 4K displays to work over HDMI.


DisplayPort (or its cousins ThunderBolt and USB-C display) are superior in almost every way, including generating far less waste heat.

Aug 20, 2020 12:19 PM in response to mateusz_d

to get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, the display will not be shown as present, and no data will be sent to the display.

 

This query is only sent at certain times:

• at startup

• at wake from sleep

• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go

on invoking Option-(Detect Display) button in Displays preferences (from another display)

 

so try doing some of those things and see if the display comes alive.


Modern Displays with multiple ports are sometimes busy scanning the other ports, looking for an input, and miss the query from the Mac. They need to pay attention to the port you are actually using, or they will miss the query.


Some displays have On-Screen Display settings that can be used to tell the display a computer is attached on a certain port, or a certain port should be highest priority. Changing those may make your display more responsive.


Some displays include their own private "sleep" settings for the display alone. This can allow the display to enter its own sleep mode, on top of the Mac's not sending it data. A display that is sleeping on its own cannot respond to the Mac's query, and will stay dark.

Aug 21, 2020 8:33 AM in response to mateusz_d

I have thought that maybe the problem is EDID, so I've also tried steps to help macOS handle EDID from monitor by adding Display Overrides in macOS as described here: https://apple.stackexchange.com/questions/221239/my-external-monitor-doesnt-work-at-full-resolution-with-my-macbook/221498#221498


Without change - monitor can't still negotiate connection with macOS.

Aug 21, 2020 9:46 AM in response to a brody

Some USB-C cables are power only. If it is the cable that shipped with your power brick, be sure to get an appropriate USB cable that can manage video. Also Some USB-C hubs only get sufficient power from the computer for data. SIIG and OWC both offer excellent hubs that offer 100W throughput and Displayport and HDMI options.

Can't connect external display to MacBook Pro

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