Macbook Air

Hi,
I have been using my late 2011 Macbook Air with OS X Lion to view movies on my LCD TV. With an adapter, I plug an HDMI cable into the Thunderbolt port and run that to the TV. The Air automatically detects the external display, and I have it set to use that as the main display when it is connected. WHen I disconnect the TV the main display automatically returns to 11" Air screen. It has worked quite well.

Today I hooked up the TV, the Air 11" display turned blue, as it normally does when the TV is detected and the main display is changing over to the TV, but then the display came back on the 11" screen. When I unplugged the TV it did the reverse, turning blue like it was resetting the display again, but the whole time it never goes to the TV. And the TV does not show up under "Displays" when plugged in, even if I run "Detect Displays".

Any suggestions?
westoneAsked:
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Owen RubinConnect With a Mentor PrincipalCommented:
Damn, I was sure this was an HDCP problem.  Do you have an Apple Store nearby? Maybe you could make a Genius appointment and let them use THEIR cable. At least you could narrow it down to the cable.  I am wondering if there is a bad pin in the cable or in the connector and the computer just does not see the TV.

You might also take your MacBook Air to a store that sells TVs, and ask if you can hook it up to see what it looks like. That way you can see if it is the TV that is causing the problem.

Good luck.
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Owen RubinPrincipalCommented:
I will suggest the obvious first. Restart the machine and reset the PRAM (Command-Shift-P-R while booting, and wait for it to reboot!) Sounds like something in the monitor parameters may have got messed up.

Also, remember the HDCP, the HDMI security protocol may fail if you connect and then disconnect and then reconnect the display without powering down the display.

A few things to be sure to try:

1): be sure everything is wired up, connected and turned on BEFORE attaching it to the Mac. When it turns blue and returns, the security handshake to the monitor failed.

2). Try turning off fully the HDTV, let it sit for a minute of so, and then, while off, reconnect it. Then turn on the HDTV. Now  connect it to your Mac.  

I have seen cases where the handshake for the security gets screwed up, and as a result, the computer does not see a display since the digital connection, which is encrypted, cannot be decrypted. It is forcing that to do a new handshake that is necessary.
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westoneAuthor Commented:
Thank you. What I am reading on the net is that display settings for Mac OS X are no longer stored in PRAM as in previous versions, so it seems resetting PRAM would not effect the issue.

I will try your other suggestion, but I am confused. You say,"Try turning off fully the HDTV, let it sit for a minute of so, and then, while off, reconnect it. Then turn on the HDTV. Now  connect it to your Mac."

After letting the TV sit turned off for a few minutes, what are you suggesting it be reconnected to before turning it on? It would seem you mean connect it to the Mac, but then in the next step you say to turn it on and connect it to the Mac. Please clarify.
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Owen RubinPrincipalCommented:
So HDCP, the (damned) security protocol for HDMI will force a disconnect if the monitor or the computer thinks the connection has been interrupted while live.

Sorry, I see that what I wrote was not clear. Yes, I mean turn everything off, reconnect the system, turn on the monitor, and then turn on the Mac.  It seems that this should never be necessary, but I have seen that interface get into some strange handshake problems.

HOWEVER, My best guess is that once you disconnect the monitor, the Mac will reset it self. After that has happened, the TV also needs to be reset, and simply powering it down disconnected, then powering it up, and then reconnecting should be good enough. If that does not work, then a full power down on both ends would have to clear both sides.

That would truly such if you had to keep doing this. I use my machine on my HDTV all the time (a Mac Mini and a MacBook Pro) but I do power down both sides between uses, so maybe why I have never seen this.

And you are right, I forgot that monitor settings are no longer in PRAM. Thanks for reminding me.
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westoneAuthor Commented:
Well I was hopeful but that didn't do it. Tried it several times, even left the TV unplugged for 3 days while I was out of town. Also tried the TV on my iMac with a different HDMI cable with same result. The only two constants are the TV itself and the HDMI Thunderbolt adapter. I hate to go buy another adapter just to had it do the same thing and turn out to be something with the TV. This sucks!
Thanks for the suggestions though.
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westoneAuthor Commented:
Those are good ideas. There is an Apple store just a few minutes from here. I'm new to Apple & didn't know that was an option. Thanks.
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Owen RubinPrincipalCommented:
Do not forget to make an appointment. Getting a spot at the Genius Bar without one can take a lot of time.

You can go to the Apple website for the Genius Bar (http://www.apple.com/retail/geniusbar/) and enter your location on the right by selecting your state and store, and then press "reserve". Then select the product you want to talk about (Mac in this case) and press next.  You will be shown the time slots available over the next few days. Pick one that works for you.

By doing this, your wait time in the store will be shorter. If you do not do this, then they fit you in IF they have a slot open up, and you could wait a long time.

Post here if you discover something new.
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westoneAuthor Commented:
Thanks for the tip, I have appointment tomorrow morning. There were several slots open this afternoon and evening but I am booked up all day.
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westoneAuthor Commented:
FYI: The problem was the Belkin Thunderbolt to HDMI adapter had gone bad. Apple gave me a new one at no charge. Thanks for the help.
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Owen RubinPrincipalCommented:
Excellent. Glad this all worked out. Thanks for the points.
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