External display not working post Yosemite

Hey dmoncur,

Sorry, I didn't quite understand the solution for this - so is there a specific HDMI cable I have to buy? Or a specific one sold with Apple TV (I don't have Apple tv)

(2OO9 Macbook Pro stopped working with Samsung TV since Yosemite)

Have same problem on MacBook Pro (Retina, Mid 2012) no HDMI connection to Sony TV after Yosemite upgrade

Same problem, macbook air 2013. every Saturday I've used my display for gatherings and today, there was much disappointment.😟

i have the same problem, the external monitor only shows noise, flickers.

disappointed

I have the same problem. MBP (Mid 2012) was working perfectly with Thunderbolt Display (27-in). Was able to keep MBP shut and use display. After Yosemite update, closing the mac means shutting display off....

I've same problem.

MBA 13" mid 2011. Samsung 8000 series tv. With mavericks everything was running smoothly.

Andrea

Have spent some time trying to solve, spoke to apple support. In the end I swapped the HDMI lead I have been using under mavericks and plugged it into my Apple TV and it worked fine? (will not work on my Macbook Pro). I Even tried installing a second boot disk with Mavericks to see if the lead still worked on Mavericks to no avail.

Plugged in the HDMI lead that was on my Apple TV into my Macbook Pro and all work fine? on both Mavericks and Yosemite. very frustrating Can only assume there is an HDMI protocol version update in Yosemite?

Same here

I also run a mid 2010 MacBook Pro with a Samsung SA550 external display. It worked fine with Mavericks but since the Yosemite upgrade I can not solve why it no longer works.

I'm having the same problem. Worked fine with mavericks. Screen acts like its getting signal but all thats displayed is black.

I'm using a mid 2012 MBP rocketfish mini display to VGA adapter and Samsung Monitor.

Anybody having this trouble with first party (apple brand) adapters? I'm thinking it maybe something with 3rd party adapters.

I also run a mid 2010 MacBook Pro with a Samsung SA550 external display. It worked fine with Mavericks but since the Yosemite upgrade I can not solve why it no longer works. i did speak with someone that is a developer and certified Apple technician and it appears there may be some missing resource packs from the OS release so I would expect an update will resolve this problem for many users.

Verifying and and repairing disk permissions fixes the problem with the display policy group but only temporarily. Once the computer is rebooted the user group is returned to 244.

MBA used to mirror on Samsung TV thru generic thunderbolt to HDMI adaptor now not recognizing tv after Yosemite update. Tried resetting NVRAM and power on/off etc nothing works. Disappointing.

I have same problem. MacBook Pro (new, 2014) upgraded to Yosemite. Had been running with ViewPoint high-resolution, 27" monitor, HDMI. I tried Thunderbolt connection -- it connected, but it would not allow the external monitor to run at its native resolution (2560x1440). It would only display properly using HDMI. Just 3 days ago after I installed the latest OSx software update, and my external monitor problems started. On startup, my MacBook screen flickers non-stop. I can fix problem eventually (after several tries) by disconnecting the HDMI cable, turning OFF the external monitor power, turning external monitor back ON and then plugging in the HDMI to my MacBook Pro. This is very inconvenient.

I will try using the Thunderbolt cable. When I tried it in the past, it connected, but it wouldn't display the native resolution of my external monitor (which is 2560x1440). Can only get this resolution now with HDMI.

I went from mavericks to yosemite and my external display would not be recognized. I was using display to VGA adapter (apple brand) Apple support were stumped and sent me in to Genius bar. As soon as we used a display port to HDMI adapter it worked. I have 2011 Macbook Pro. I tried everything, rolling back to Mavericks from Time Machine etc. It was only when we used a belkin display port to HDMI that Yosemite recognized my display and gave me all the resolution options. Back in business. By the way I am using a Philips 244e external display. Hope this helps.