I meet the same problem with the connecting to my TV.
Until Mac OS X 10.10.2 it was possible to connect my iMac Mid 2007 to my TV Philipps UVSH. For that, I used the Mini-DVI to Video Adapter. It worked very good. The quality of the image was perfect.
But, since the last update to Mac OS X 10.10.3 the TV doesn't show anymore the screen of the Mac. The Mac itself doesn't react, as it done before when the screen changed a little bit.
I called the Apple Support. Their Answer: because I use a beta version, they aren't able to help.
I went to an Apple Store, they have advice to buy a new Mini-DVI to Video Adapter. But even the new adapter brings no change.
I have not seen in the informations about Mac OS X 10.10.4 that Apple have solve this problem.
Does someone have an advise to give me?
Sincerely yours.