Macbook Pro *thinks* it's mirroring video to my tv via DVI but....

one234hone234h Downingtown, PA [USA]
edited April 2012 in Hardware's not.

The Players:
A) It's an older Macbook Pro running OSX 10.4.11. The screen is not backlit, but if I shine an LED flaslight obliquely at the display, I can just make it out, so it's still booting and everything's there.
B) TV is an LG plasma made in 2010. I've output video to my tv through vga using other laptops before.
C) The dvi cable & dvi-to-vga adapter are both spank'n new.

The Saga:
DVI & said adapter are plugged into to the Macbook and the tv respectively.
I go into OSX's Display Preferences and Arrange the displays, and click turn Mirroring On. OSX recognizes the tv as an LG, and everything. OSX thinks everything's A-OK.

My tv, however, asserts that there is NO SIGNAL coming in its RGB-PC input. TV conveniently "grey's out" the ports which have nothing connected to it in its Input menu, and this one is is not; it is able to be selected which tells me the tv knows on some level that something's there.

This isn't some deep-seeded PC/Apple/LG compatibility issue, is it?

Cables seem securely connected.

Initial web searches are unproductive.

What do you all think, Icrontic?

[Edited for increased clarity.]


  • lmorchardlmorchard {web,mad,computer} scientist Portland, OR Icrontian
    Problem with this stuff on MBPs is it tends to work... or not at all, and give no clue as to why.

    Have you tried it without mirroring, by chance?

    FWIW, I've gotten all the above working before with an MBP -> DVI-to-VGA dongle -> VGA cable -> Westinghouse HDTV, both MBP and HDTV circa 2009. So, it's possible with that combination anyway. Which, of course, says nothing about an LG HDTV
  • one234hone234h Downingtown, PA [USA]

    Had some family issues recently but all settled. Thank you very much for the response; I just haven't been home to try this way. I should be doing by this evening and I'll edit my post to update with the results. I just didn't want you to feel like you were posting into a black hole.

    Thanks for your time and effort!
  • one234hone234h Downingtown, PA [USA]

    Didn't see before you used a dongle. I've never used one before. You connected it the vga cable? I thought dongles were wireless? I've managed to get ftp access to the MbP from my other laptop so I yanked the necessary files, but it's still a better machine than paperweight.

    If you could elaborate more on the dongle...

    (Never thought I'd say that... :P )
  • TushonTushon I'm scared, Coach Alexandria, VA Icrontian
    edited May 2012
    He is talking about something like this

    which is presumably similar to what you already have.
  • one234hone234h Downingtown, PA [USA]
    edited May 2012


    No no.

    My hardware looks like this. They're not, ya know, not Jobs-inatd. They're just... cables.


    Also, crap on me. I meant SVGA. Wow. This could be part of the trouble.
  • TushonTushon I'm scared, Coach Alexandria, VA Icrontian
    edited May 2012
    Well, how would I know? :P

    Seems relevant below:
    I connect to the TV with a mini DVI to VGA using the TV PC input. Initially I had the same problem with the computer recognizing the TV, but the TV not showing the PC as an input. I fixed this by going into the TV menu and changing the PC input to "Always available." This worked to get the computer screen on the TV, but the picture wasn't full-screen. To get the picture-fullscreen, I took the computer our of mirror mode and turned the TV Display setting to "Full 1." I have a black macbook rather than a Pro, but thought this might still help. Good luck.
    I had the same problem with a 1080i Bravia Sony and a MacBook Pro connected with a DVI-HDMI lead - it turned out to be a very simple solution - you have to make sure you are looking at the right AV channel on the TV. The mapping of AV1-6 to the ports on the back is not obvious at all (in this case it was AV4 that was the correct AV port). The Bravia also has the option to skip AV channels if desired - so if in the preferences you have disabled ports then you need to make them available to skip through.
  • one234hone234h Downingtown, PA [USA]

    Thanks for checking the Apple forum for that; I never stopped to consider it an Apple issue since the computer seemed to be the only thing working!

    I am going to have to take a trip back to Radio Shack to return my larger sized DVI and get the mini-one, (maybe online if RS doesn't carry it).
  • TushonTushon I'm scared, Coach Alexandria, VA Icrontian
    Well, I would try the "Always available" thing first, but that's just me.
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