External display not detected after upgrade

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Level 1

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External display not detected after upgrade

I have a Samsung SyncMaster P2450 connected via HDMI to my MacBook Pro (15 inch, Retina, mid 2015).

This second display functioned as intended until upgrading from Yosemite to El Capitan this afternoon.

I have opened the displays preferences panels and held the ALT key to expose the "Detect Displays" button, but clicking that button did not solve the problem.

I have tried all toggles on the monitor itself that I can think of, but to no avail.

Any ideas would be greatly appreciated.

Thanks in advance.

MacBook Pro with Retina display, OS X El Capitan (10.11)

Posted on Oct 1, 2015 12:48 PM

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Answer 1

Pmintz25

Level 4

2,058 points

Oct 1, 2015 12:58 PM in response to texcandss02

With the display connected, check for software updates. There may be an update related to externals that does not happen until an external is connected.

Does the display on your MBP flicker or change at all when the display is unplugged and then plugged back in? Or does it simply do nothing? Try restarting the computer without the display connected and then connect it once you've logged into your account. Look for any screen activity such as a resolution change. If literally nothing happens on your computer then the display isn't being detected at all.

Note that Samsung's website doesn't show any available drivers for Mac at all. Even though it's worked in the past, it may not be supported with the drivers they provide.

http://www.samsung.com/us/business/support/owners/product/P2450H

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Answer 2

texcandss02 Author

Level 1

0 points

Oct 1, 2015 1:12 PM in response to Pmintz25

Hi Pmintz25,

Thanks you kindly for the thoughts. I did try to check for updates - nothing.

Tried all suggestions - no luck. No screen change, flicker etc. on power on/off, cord plug/unplug etc.

When I click "detect displays" the screen on the macbook does flicker for a brief second but returns immediately to its regular state.

Thanks!

S.

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Answer 3

Oct 1, 2015 1:20 PM in response to texcandss02

With the external display connected and powered, try a PRAM reset as described here:

https://support.apple.com/kb/PH21876?viewlocale=en_US&locale=en_US

Reseting PRAM can often fix peripheral connection issues.

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Answer 4

Pmintz25

Level 4

2,058 points

Oct 1, 2015 1:26 PM in response to texcandss02

I did some forum browsing on some 3rd party sites and a lot of people are having issues with displays connected via HDMI. Try connecting them using a different method if possible and see if that works. Sounds like something works for some people and not for others. Hopefully Apple will get enough calls about it and will get it fixed.

When you download new OS software, Apple will grant you some free phone support if you call and ask. If you get time you can call them and see if they have some tricks they aren't telling us.

Now I'm going to go home and try connecting my TV to my rMBP and see what happens.

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Answer 5

wbtittle

Level 1

4 points

Oct 6, 2015 8:08 AM in response to texcandss02

https://www.youtube.com/watch?v=_QmXLk6PRxc

I followed these guys directions and it caused by external display to start working again. It also fixed my fail to wake from sleep problem.

The part I missed the first time around was removing all devices except keyboard. In zapping PRAM I had to use a USB keyboard. The Bluetooth wouldn't work...

Finally, after resetting SMC, I failed to plug my monitor back in.... I stared blankly at the HDCP connector sitting there unplugged.

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