HT201834: Use your Mac notebook computer in closed-display mode with an external display

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GrowingViolet

Q: External monitor loses signal when closing clamshell; can't wake except by opening back up

I am using a MacBook 5,1 (13" Aluminum Unibody, late 2008) under OS X Yosemite 10.10.3 with a Lenovo L200pwD external monitor hooked up through Mini DisplayPort to VGA (no other adapters are in use).  I am using a wired mouse and keyboard, each hooked up independently via USB.

 

When booting up the computer with these devices all attached, everything functions as expected... until I close the clamshell, at which point the external monitor loses a signal, and trying to use the keyboard or mouse provides no response.  Opening the clamshell back up returns me to the login screen, with the image appearing on both displays as before, and the mouse and keyboard working again.

 

I have used this exact setup previously with success, so I'm a bit baffled as to what could be causing this.  The only thing that I could think I have done differently is that, previously, I attached the keyboard, mouse, and monitor inputs after having already booted, rather than before.  I will try that and see if it makes a difference, and update this post accordingly.

 

Any assistance is greatly appreciated!

 

Edit1:  I tried turning off the computer, unplugging the inputs, and booting back to the desktop before plugging them in.  Upon closing the clamshell, it worked! I had a single-monitor desktop on the external display!  But then, inexplicably, it blacked out again.   I'm no less baffled than before...

 

Edit2:  I may have solved it...?  I realized there was indeed one other thing that was different -- I didn't have the MacBook plugged in to power.  After plugging it in and trying again... it's now working. This makes no sense to me... it's okay with running two displays at once without power, but one external display is just too much?  Bizarre!  I guess this is solved now, though if anyone has any further insight into what's happening here it is still appreciated.  Either way I will leave this post in case anyone else has a similar issue.

 

Message was edited by: GrowingViolet Additional troubleshooting steps taken.

MacBook, OS X Yosemite (10.10.3), Cassandra

Posted on Sep 3, 2015 6:53 AM

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Q: External monitor loses signal when closing clamshell; can't wake except by opening back up

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