Macbook pros to TV not working

Question

I've been connecting my two Macbook pros (2008 & 2011 both on OSX) to a Sony Bravia TV for ages using a HDMI cable connected to a HDMI adaptor to Minidisplay.  For some reason now the connection doesn't work.  I've tried both computers, different HDMI cables, different adaptors, different ports on the TV (and entertainment center), and nothing works.  When connected directly to the TV the screen remains blank, the laptop will flicker when the cable is first connected but then nothing.  The laptops don't recognize the second screen at all.  I've tried resetting the PRAM, unplugging and plugging, turning everything off and on, and restarting the laptop.  Nothing has worked so far.

Answer 1

If your Mac is capable, look in System Preferences > Sound > ouput tab and select the TV or hold the Option key down and click on the Volume icon on the menubar to accomplish the same.
Here are the models that pass sound over HDMI and those that don't.
These Apple computers supply multichannel audio (up to 8 channels) and video signals over Mini DisplayPort:
iMac (Late 2009) and later
Mac mini (Mid 2010) and later1
Mac Pro (Mid 2010)
MacBook (Mid  2010) and later
MacBook Pro (Mid 2010) and later
MacBook Pro (Retina, Mid 2012)1
MacBook Air (Late 2010) and later
1No additional adapter is necessary if you are connecting directly to the HDMI port on your Mac mini (Mid 2010) and later or your MacBook Pro (Retina, Mid 2012).
These Apple computers supply only video signals over Mini DisplayPort:
iMac (Early 2009) and (Mid 2009)
Mac Mini (Early 2009) and (Late 2009)
Mac Pro (Early 2009)
MacBook (Late 2009)
MacBook (13-inch Aluminum Late 2008)
MacBook Pro (late 2008), (Mid 2009), and (Early 2009)
In addition you need a MiniDisplay Port to HDMI adapter that passes audio like this:
http://store.apple.com/us/product/H1824ZM/A/Moshi_Mini_DisplayPort_to_HDMI_Adapt er