How to force a MacBook Pro to re-detect video?

December 11, 2007 3:36 PM

How to force a MacBook Pro to re-detect video?

When moving my Macbook Pro between my Dell 24" and my LCD TV, I've been having some detection problems. If I unplug the monitor while the computer is still on and plug into my LCDTV (VGA), the screen is blank on both the TV and the and MacBook Pro built-in screen.

The only way I can get it to work is:

* Completely shut down the computer
* Unplug DVI
* Connect to LCD TV (DVI/VGA)
* Boot computer

Is there a keyboard command to redetect video sources (such as the PC FN+F8).... or.... is there a way that I can change my MacBooks video source without rebooting? The old Powerbooks seemed to do this seamlessly.

posted by colecovizion to Computers & Internet (10 answers total)

Have you tried simply putting the Powerbook to sleep and then waking it up? Try either selecting Sleep in the Apple menu, or shutting and reopening the laptop.
posted by phaedon at 3:45 PM on December 11, 2007

Best answer: Try hitting F7 or (depending on your F-key settings) hold function and hit F7. This should switch between "mirroring" and "spanning" modes and might trip the projector on.

Failing that, this support thread might have some ideas for you.

Good luck!
posted by churl at 3:55 PM on December 11, 2007

Er, by "projector" i meant "external display/tv". Whoops.
posted by churl at 3:56 PM on December 11, 2007

Control Panel -> Displays -> Detect Displays doesn't work?
posted by procrastination at 4:12 PM on December 11, 2007

Response by poster: Thanks for the replies so far. I'll wait until I get home to try some of them. For clarification, I get in this rut where I can't get any screen to show anything, so I really need to find a solution that doesn't involve an already working screen. A lot of the time, I can't even get it to sleep because it thinks there is an external display with the lid shut.
posted by colecovizion at 4:38 PM on December 11, 2007

Oops, "Control Panel" should of course be "System Preferences". Too much time on a PC today.
posted by procrastination at 4:42 PM on December 11, 2007

When you unplug it from your Dell monitor, does the main macbook screen remain on? You should see a small flash a couple seconds after you unplug the monitor as it "releases" the display.
posted by pmbuko at 5:25 PM on December 11, 2007

Seconding procrastination's Displays->Detect Displays suggestion, even if the screen is blank.

Before you unplug your monitor go to your MacBook's System Preferences->Displays and hover the mouse cursor directly over the Detect Displays button. Then, once you've made the switch to your LCDTV, click the unseen Detect Displays button and hopefully you'll be back in business.
posted by Izner Myletze at 5:31 PM on December 11, 2007

You can also add displays to the menu bar and quickly be able to change the resolution or detect displays.
posted by ooklala at 7:03 PM on December 11, 2007

Response by poster: Wow, I didn't realize how bad this problem was until I read some of the discussions about it, especially here.

It looks like this issue is unresolved and Apple isn't admitting it.
posted by colecovizion at 10:13 AM on December 12, 2007