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MacBook Pro 8,1 (13", i5 2.3Ghz) - when I connect an external screen through a MiniDP -> DVI adapter the Mac detects it (knows it's a Samsung SyncMaster and lets me change its resolution) but doesn't show anything on screen. Even though the Mac thinks that the screen works properly (I can move the cursor out of the Mac's screen), the external monitor's led blinks as there was no signal at all. Changing screen resolution doesn't help.

I've browsed many similar questions on the internet, unfortunately most of them suggest upgrading the OS. I'm using Mac OSX 10.6.8 Snow Leopard. What should I do?

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Have you had this display working with another system? Have you had the Mac and display adapter working with another display? When you reboot the mac, during the boot process does the external display show anything? –  macaco Sep 14 '11 at 12:01
    
Works with my another computer, doesn't show anything during the boot. –  Paul Sep 14 '11 at 12:56
    
Did you try the MiniDP->VGA? Another thread is, I have later 2008 MBP 15", with two display chips (one is built in with shared memory). If I connect it to an external monitor, but using the built-in display chip, the external monitor doesn't have any signal. If I switch to the stand-alone display chip, it then works fine. –  kukoo Sep 14 '11 at 15:06
    
Thanks for this thread folks. Very close to what I am experiencing with my 17" MBP. Just started today. I plug in my external monitor (a company issue NEC) and the MPB monitor disappears. I cannot move the cursor to the MBP monitor. I unplug the external monitor and it switches back to internal. I tried detecting displays with both plugged in but it won't pick up the internal screen, only the external NEC (an accusync LCD223WXM). Thanks in advance. –  Greg Feb 9 '12 at 14:06

3 Answers 3

up vote 9 down vote accepted

I had the same problem, and I think I found what causes the problem. My macbook air was detecting the display, but only thing I saw was black screen.

Either your monitor is using VGA signal even if you are using DVI cable or you are using DVI to VGA adapter in between. MiniDP to DVI only produces digital signal.

For more information check a blog post of mine.

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I should give credit where credit is due. Your answer is right - I was using a MiniDP to DVI adapter, and then another one, DVI to VGA. That caused the problem. Connecting a DVI monitor to my MBP resolved the issue. –  Paul Nov 8 '11 at 16:31
    
an upvote is fine too :) I am glad it helped –  nimcap Nov 8 '11 at 17:37
    
Would upvote the answer, unfortunately I'm not allowed to as I'm not a registered user. –  Paul Nov 9 '11 at 9:31

This most likely means the Mac is outputting a video mode that the screen can't display. Try reducing the resolution and Refresh Rate (in System Preferences -> Display) until you get something on the screen, then work your way up the list again. A good starting point would be 1024x768 or even 640x480.

The other possibility would be that the signal isn't arriving intact, either due to a cable/plug fault or that the screen or Mac have a hardware fault (which you can rule out by connecting the Mac to another DVI screen with the same adapter and by connecting the monitor to another computer).

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Even at 640x480 the external monitor receives no signal. I've just tried rebooting my mac with no luck - no signal during the boot process. The screen works just fine with my old Mac Mini. Tomorrow I'll try the adapter with another monitor. –  Paul Sep 14 '11 at 12:55
    
When testing, make sure you test the same input, in case it's a monitor with multiple inputs (just because the VGA input works doesn't mean the DVI input also does). –  Ingmar Hupp Sep 14 '11 at 13:33

I've had the problem as well and only by resetting my monitor am I able to get it to work.

Other posts suggesting it is something to do with the PRAM, but I've not seen the problem being on the Mac end of things. As this problem is persistent, so it seems I will have to reset the monitor each time so it recovers from the failure, but doesn't seem to address the root cause so I have yet to find a more permanent fix.

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It never occurred to me that I need to reset my Samsung SyncMaster 2494LW monitor. I been trying to read various posts & solutions of the last hour. I was ready to give up when I read that you recovered from this failure (at least temporarily) by resetting. I tried & now I am able to enjoy my old external monitor with my MBP 13". Thanks! –  user52357 Jun 30 '13 at 5:41

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