External monitor not working under Mountain Lion

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equinox1979 Author

Level 1

25 points

External monitor not working under Mountain Lion

My external display (Samsung 23") is not working since I updgraded to Mountain Lion, even though the same setup worked when my MacBook Pro and Air were running Lion.

I already have resetted the PRAM as suggested in other threads with no change. Interesting enough, this behaviour seems to be depending on the cable length.

With a 1m Mini Display Port to DVI Cable I could use my external monitor, unfortunately this cable is far to short for my desk. A 3m Mini Display Port to DVI Cable failed in 100% (up to now) of all tries to detect the external display properly. My original setup with a Mini Display Port to DVI connector and a DVI cable seemed to work only in 20% of all cases.

Both Macs detec that an external display has been connected and also react to switching the external display on and off when it is connected, the laptop screen changes to the typical blue, but then it returns to its normal state.

MacBook Pro is a mid-2010 15" device, the Air a 2011 11" device, both running 10.8.1.

Any ideas would be greatly appreciated.

MacBook Pro, OS X Mountain Lion (10.8.1), Mid-2010

Posted on Aug 23, 2012 9:56 PM

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Answer 1

xa4SCE

Level 1

0 points

Aug 24, 2012 3:34 AM in response to equinox1979

Hi equinox1979,

not sure whether this is related to the same issue I am experiencing since applyting the 10.8.1 software update.

When I reboot my MacBook Air 13" model 2011 (MacBookAir4,2) with the Samsung SMS23A350 connected through a thunderbold/HDMI cable, the system hangs on the light gray screen with apple logo (after entering my password to unlock the laptop).

Booting with the HDMI cable disconnected works fine. I can connect the monitor again once the MBA is rebooted.

Seems that 10.8.1 has broken something...

kidn regards,

Xavier

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Answer 2

equinox1979 Author

Level 1

25 points

Aug 26, 2012 1:17 AM in response to xa4SCE

Yeah,

it indeed looks like something got messed up given that everything worked fine under Lion and SL.

I waited for 10.8.1 and hoped it would resolve my issues, unfortunately that was a bummer. Let's wait for 10.8.2; as I indicated above PRAM reset or other techniques already suggested in the forums did not help.

Now I need to look after my Time Capsule. Apple seems to have had fun with Mountain Lion ;-)

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Answer 3

equinox1979 Author

Level 1

25 points

Sep 16, 2012 9:43 AM in response to equinox1979

Another piece of information; I checked my system logs and found this entry repeating once I tried to connect my external display:

16.09.12 18:26:45,972 System Preferences[14205]: CGSGetNumberOfDisplayModes: Invalid display 0x41dc9d00

16.09.12 18:26:45,973 System Preferences[14205]: CGSGetCurrentDisplayMode: Invalid display 0x41dc9d00

16.09.12 18:26:45,973 System Preferences[14205]: CGSGetNumberOfDisplayModes: Invalid display 0x41dc9d00

16.09.12 18:26:45,973 System Preferences[14205]: CGSGetCurrentDisplayMode: Invalid display 0x41dc9d00

16.09.12 18:26:45,979 System Preferences[14205]: CGSGetNumberOfDisplayModes: Invalid display 0x41dc9d00

16.09.12 18:26:45,980 System Preferences[14205]: CGSGetCurrentDisplayMode: Invalid display 0x41dc9d00

16.09.12 18:26:46,003 System Preferences[14205]: CGSServiceForDisplayNumber: Invalid display 0x41dc9d00

16.09.12 18:26:46,009 System Preferences[14205]: CGSServiceForDisplayNumber: Invalid display 0x41dc9d00

I really do hope that 10.8.2 is going to adress this issue. Up to that point Mountain Lion has rendered my external display completely useless...

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