Comments on: How to force a MacBook Pro to re-detect video?

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

colecovizion — Tue, 11 Dec 2007 15:36:04 -0800

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.

By: phaedon

phaedon — Tue, 11 Dec 2007 15:45:43 -0800

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.

By: churl

churl — Tue, 11 Dec 2007 15:55:37 -0800

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!

By: churl

churl — Tue, 11 Dec 2007 15:56:53 -0800

Er, by "projector" i meant "external display/tv". Whoops.

By: procrastination

procrastination — Tue, 11 Dec 2007 16:12:18 -0800

Control Panel -> Displays -> Detect Displays doesn't work?

By: colecovizion

colecovizion — Tue, 11 Dec 2007 16:38:46 -0800

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.

By: procrastination

procrastination — Tue, 11 Dec 2007 16:42:07 -0800

Oops, "Control Panel" should of course be "System Preferences". Too much time on a PC today.

By: pmbuko

pmbuko — Tue, 11 Dec 2007 17:25:36 -0800

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.

By: Izner Myletze

Izner Myletze — Tue, 11 Dec 2007 17:31:22 -0800

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.

By: ooklala

ooklala — Tue, 11 Dec 2007 19:03:12 -0800

You can also add displays to the menu bar and quickly be able to change the resolution or detect displays.

By: colecovizion

colecovizion — Wed, 12 Dec 2007 10:13:40 -0800

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.