I have a mid-2010 iMac and have been using a Sony LCD-TV as an external display ever since I bought the aforementioned computer. It has been connected to the iMac via HDMI-cable and Mini Display to HDMI adapter (both brand-name quality products). After the 10.10.3 update and it's supplemental update concerning a video driver problem my iMac stopped detecting the Sony. I don't think this happened instantly after the update but very soon after. I tried everything including checking the connections and cables, checking the Sony and the HDMI slot in question, running Onyx Automation, doing PRAM and SMC resets, booting to safe mode to see if it was a resolution problem etc. Nothing worked. Then I came across a few threads on the Apple support forums and it became clear that the problem was with the 10.10.3 update. Apparently there are loads of Apple users who are either unable to get their Macs to detect their external displays or who experience problems in their external display such as screen flickering. It has been suggested that Apple might be dropping support concerning older Macs and their video drivers or at least heavily prioritizing newer computers. Currently I'm faced with either accepting the situation (at least I can use my AirParrot/Chromecast combo but it's not same by a mile in terms of functionality and performance) and hoping for Apple's next update to solve this issue or rolling back to 10.10.2 (this would mean using the Yosemite installer to do a clean install and then running the 10.10.2 combo update) which would be time-consuming. Of course I'm hoping that someone would come up with a temporary fix. One forum member suggested that I should try to cover pin number 19 (hot plug detect) on the HDMI male that goes to my Sony with a piece of tape. I tried it and it didn't work. However, I accidentally covered up pin number 2 (TMDS Channel 2 -) on my first try (I had the HDMI male upside down in my hand) and the iMac did detect the Sony although I still got no picture. Please discuss this issue! Suggestions for a fix are more than welcome. I posted this thread to this sub-forum as this isn't an iMac issue but a OS X issue that concerns iMacs, Mac Minis and Macbooks alike.