LCD Faded to Green!!!

in Genius Bar edited January 2014
Hey there,

I have an iMac G4, 1GHz, 1GB, 80 GB. I took it into an Apple Retail Store last week to have the neck replaced. I've had the computer back up since sunday and now every once in a while the whole screen will fade to this hazy green color. It wasn't doing this before I took it in and it has me kind of worried.

I've run the Apple Hardware test and TTPro 4.0.3 - both tell my my VRAM is functioning properly and that my logic board is okay. I've zapped the PRAM and tried playing with the ColorSync. It's definitely got to be on the hardware side, but I don't know whether this is a cable not set right or my logic board.

In any case, does anyone know what the cause might be and what course of action I can take? The repair was warrantied by Apple for 90 days, but the computer itself is out of warranty and I have no Apple Care for it.

Also, thse seem like the same things that caused Apple to replace the PowerBook Logic boards ... is there anyway for me to let them know about the problem?

Thanks for the help...


  • Reply 1 of 5
    It sounds like the cable that connects to the monitor is off somehow. This could either be that one side is not properly plugged in, or that the cable has become pinched. There is a good chance that this happened while in service, I would guess that they had to replace the whole case, and while re-assembling the cable got giggled.
  • Reply 2 of 5
    neutrino23neutrino23 Posts: 1,560member
    Definitely a cable issue. Call them back immediately.
  • Reply 3 of 5
    Thanks for the suggestion. I'm taking it to an Apple Service Center today to have them crack it open and fix it.

    However, is there a sure-fire way to know that it's not my graphics card overheating or doing something weird? \

    Oh, and just curious, but what make you certain it's a cable? Graphics cards aren't really my area of expertise on a Mac, so I really have no idea what's going on...

    Thanks again!
  • Reply 4 of 5
    The reason i am heavily leaning towards the cable is that you are shifting into a single color. The only place where the colors are physically isolated like that are in the RAMDAC (a chip that connects to the cable in question if things are done in analog... I don't think there is one involved, but there is a congrut), the cable, and the actual LCD panel.

    If the traces on the panel are going, then you are hosed. But that is usually an either/or thing... it either works or it doesn't. You don't usually get changing behavior.

    The RAMDAC... well that is all silicon with some capacitors. Theoretically you could get some fluctuations from the capacitors... but this is a low probability for failure. Chances that you would have problems like this in the digital parts of the video card are really low. Overheating is the one issue, but there you tend to get really wild behavior or outright failure.

    The cable... well... it is a cable, the most common source of fluctuating problems. And the fact that it happens to carry the three different signals (one for each color) separately (different wires) tends to make this failure mode easily explainable. The fact that said cable is going through a fairly tight space that moves (the neck) that just got replaced and has a few joints (read: placed where it could get pinched) just makes the whole thing a near lock.
  • Reply 5 of 5
    Thanks for all of your insight. It's always nice to learn something new about my Mac. I did take it to a service rep today that confirmed it was more than likely a cable problem.

    I feel much better now ... other than the fact I'm out of comission with my iMac until Tuesday and stuck using my roommates Averatec Laptop

    Thanks again for the insight!
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