I solved the problem. Your computer is detecting the display, but it's outputting the wrong ratio so the screen is not able to display the information it is sent. For some reason, when you open the display preferences for the external screen and turn off mirroring, lion places the preferences for your external display in the middle of your external display - meaning that if the settings are wrong, you can't see it!
The solution is to press the "gather windows" button, which will bring the display settings back onto your main monitor. The. You can find the aspect ratio that works for your display.
So i found a way today of getting my monitor to work with my macbook pro 13"... hope this helps someone else!!
1. Plug in mini diaply port adapter with no dvi/vga conected
2. Make sure dvi/vga is conected to monitor and monitor is on or at least ready to turn on with signal
3. Turn on macbook wait for it to boot up
4. Change the resolution of your macbook screen to the resolution your screen wants (mine was 1024x768 fairly standard and should work for most people)
5. Plug in dvi cable to the display port adapter
6. My screen would then refresh showing on both screen (extended desktop)
7. Change macbook resolution back to origional and all is good!!
Let me know if it works for you...
External Display (Any: Projector, TV, LCD Monitor) don't show any image from Mac Book Pro with BootCamp Windows 7 or OSX 10.6, even if external harware is detected. Erratic behavior.
Change Vertical Refresh Rate manually.
On Mac I can't find a video but maybe in System Preferences: Displays.
Important: Check valid values for refresh rate on your Display user manual, this parameter should be automatic but for some reason you have to update manually.
Hope it helps.
MacBook Pro 2011
OSX 10.6/ BootCamp Windows 7
TV LCD LG 42"
Sony 3LCD Proyector
Acer LCD 15"
This worked for me! I TRIED EVERYTHING!@!! pram, settings, deleting files, osx wipes, etc different resolutions.... for me I just have to UNPLUG the monitor power cable, then plug in my cable...(get the little blue screen) then when it comes back, plug the power cable back in. Detects it everytime... so crazy, apple needs to fix this tho...
Much the same problem as everyone else. Bought a new 13" MBP in March would'nt connect to external monitor. Managed to get working with help from Apple Support as it was new machine. They said the Thunderbolt port had not been enabled. Lots of rebooting etc. Now following upgrade to 10.7 no longer works, just get the flashing blue screen and no cable on the external monitor.
Have got presentation to do on this in about 3 mins and not working. This sort of thing used to just work on Macs and was what made us feel good about the brand at a time when getting windows to do external displays was tricky, the tide seems to have turned. Need this resolving please Apple.
One more for the growing list...
Macbook pro 13" 2010, worked fine with a number of displays using HDMI connection through the Apple approved adaptor.
Then a week or so ago it just stopped working. Tried all of the fixes described in this thread (and a number of others) to no avail. Thought the latest software update might fix it but that's come and gone with no improvement. What the hel* are Apple doing not even posting an acknowledgement and a comment along the lines of 'We know it's a problem and we're working on it, stay with us...'? There are a number of threads all talking about the same issue so it doesn't seem to be a rare problem.
Very poor show.
I'm posting a solution in which I was initially very dubious.
I have a 13" MacBook Pro 5,5.
Was working fine with an external ViewSonic monitor using an Apple branded mini-Display port to DVI converter. This adapter was purchased new and only plugged in about 15 times total.
Then I upgraded to Lion and the external display quit working. I posted my issue to a variety of help forums. It seemed many folks had the same "after upgrading to Lion my external display quit working" issue.
I tried all of the suggested fixes.
Since my expensive Apple mini-display port adapter was so new, I never figured it could be the problem, however, my options were running out for troubleshooting.
I purchased a new mini-display port to DVI Apple video adapter.
Voila! It worked. My monitor recognized the video signal right away.
I have a brand new Apple Mini Display Port to DVI and it failed to work right out of the box. I can't believe there are that many DVI-MDPs that are buggy.
Some times the monitor will show up right at startup, but more times than not, I have to use the unplug power+unplug DVI-MDP and replug routine to get it up and running.
Still think it is a software problem, but not sure. Still not sure why the unplug and replug procedure works, but it seems to be a recognition problem between monitor and computer.
Same issue here. I just had some success shutting down Automatic Graphics Switching in System Preferences > Energy Saver. I shut that off, and then the Mac discovered the monitor it has happily been working with for months now. It might just be a fluke, but that did the trick this time.
Now, for the day that you could switch to just an external monitor without having to suspend the whole system... that will be a glorious day.