Hi all,
I am having an issue where, usually after I wake up my mid-2012 MacBook Pro, I get display interference on the external display. If I undock my MacBook and open it, there is no interference or distortion on the built-in display. I am not sure where to start. It is intermittent and not really replicable, but has happened a few times now.
Thanks!
MacBook Pro, OS X El Capitan (10.11.1)
Hey stimm32,
Sorry that you are having issues with your MacBook pro and an external display. To get it sorted out, I would look at the troubleshooting I have outlined below. It will have you check the cables and settings as well as the SMC and NVRAM.
Get help with video issues on external displays connected to your Mac
https://support.apple.com/en-us/HT201177
If the display image is blank or unusable
Try these steps if you don't see an image on your display. These steps can also help if the image on your screen repeatedly turns on and off (flickers), if horizontal lines appear (snow), or if the image is distorted (torn or scrambled).
These steps likely won't help if the issue is only happening in one app. If you see similar issues in only one window or app, check with the app's developer for updates or more help.
Check connections
Check the connections to your Mac and external displays:
- If you're using an Apple notebook, try connecting its power adapter.
- Make sure the external display's power cable is securely connected and that your display is turned on.
- If you're using a Mac Pro (Late 2013) make sure your displays are connected to the right ports.
- If you're using a display hub, switchbox, or "KVM," try connecting your display's video cable directly to your Mac instead.
- Disconnect the video cable where it plugs into your Mac, then plug it back in to reseat the connection.
- If you're using a video adapter, unplug the video adapter from your Mac, then plug it back in to reseat the connection.
- If you're using more than one video adapter to connect your display (the adapters are "chained" together), try connecting the display using only one adapter if possible. Some video adapters can't be connected together. For example, a mini DisplayPort to DVI adapter can't be connected to a DVI to HDMI adapter.
- If your display has more than one video connection, see if using another connection on the display works. If possible, check to see if using a different display or a different adapter works.
- Try using a different cable that you know is in working order. Check with the display's manufacturer to make sure you're using the cable they recommend.
Adjust video settings
If there's no image on your display, try adjusting your display's brightness or contrast. If there's still no image, or the image appears torn or scrambled, try selecting a different video resolution in System Preferences.
Adjust brightness
- If you're using an Apple Display, press the increase brightness key
on your Apple keyboard. To adjust the brightness of a secondary display, press Control-F2.
- If you're using a display that's not made by Apple, check the documentation that came with your display to see if it includes built-in controls for adjusting its brightness or contrast.
Change your display resolution
- From the Apple menu, choose System Preferences.
- Click the Displays icon.
- Click Default for display. If you see more than one resolution listed, choose a resolution and refresh rate. If the display turns off when you change resolutions, press the escape key to undo the change.
If you can't change the resolution of your display because you can't see an image, restart your Mac in safe mode to reset the display resolution to defaults.
If starting in safe mode doesn't resolve the issue, reset your Mac's NVRAM and SMC to reset the video ports on your Mac to their defaults.
If that does not work, then you might want to contact Apple Support for further assistance.
Take it easy
Display interference/distortion when connected using Henge Dock
