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Thread: Looking for someone who wants help to resurrect their video-less iMac DV...

  1. #1

    Member Since
    Jan 02, 2007
    Looking for someone who wants help to resurrect their video-less iMac DV...
    Hello! I am new here, but not so new to Macintosh computers. The reason for this post is that I am developing a CD and some associated documentation for people that have corrupted the Open Firmware in their iMac DVs by some means or another and I would like to help people that might need it, while they help me to test my findings.

    I know that this is probably an old, well-documented problem, and the affected machines are probably in landfills or in the hands of those more knowledgeable or with more time to "play," but I have bought one of these machines and thought that it would be a fun last-day-of-vacation project to make a bootable CD that would magically fix it in one easy, electrocution-free step.

    The machine has not arrived yet, but I am characteristically impatient and also would like to help anyone else who might be having this problem.

    Now for the details:

    The problem - iMac DVs that were upgraded to a version of OS X without having been upgraded with a 4.1.9 firmware lose their video. You would not think this would be a common occurrence, but for some reason (possibly a Jaguar bug?), it is.

    My solution - with a lot of help from some NetBSD/macppc documentation, I was able to create a bootable HFS CD which injects the forth code required for the OF upgrade. I had some knowledge of this from the past, because I have a bad habit of losing my Mac OS 9 CD *after* I format the hard drives of old iMacs... This solution takes the CD that I created for that problem a step further by (hopefully) not requiring any Open Firmware interaction.

    Anyway, if this situation applies to you, I'd be more than happy to help you to get up and running so that you don't have to sell your still-full-of-life iMac for parts. Let me know and I can send you the link to a small wiki page I've created with the files and details.

    And, if this topic has been addressed previously in better detail, I apologize for repeating it. I just wanted to provide a concise, reliable fix for myself and others.

  2. #2

    Member Since
    Jan 02, 2007
    Process for making the CD...
    My web server is having some disk failure issues, so I thought I would just post the actual information here.


    == How I made this CD ==

    * Download the [[|OpenFirmware Updater]]
    * Extract and rename the OpenFirmware FORTH script. It is the file called "iMac Firmware" in the root of the disk image above. Talk about over-complicating things, Apple! (I just called it slfw below...)
    * Create a CHRP startup script to point to the previous step's file. I called mine 'boot.b' and it looks like this:

    Matt's iMac DV repair CD
    boot cd:,\boot\slfw

    * Create a .list file for mkisofs. I called it 'boot.list' It is pretty simple and it looks like this:

    .b Raw 'UNIX' 'tbxi' 'bootstrap'

    * Create your CD file structure

    | -- ./boot.list
    | -- ./cd_contents/
    | -- | -- ./boot/
    | -- | -- | -- ./boot.b
    | -- | -- | -- ./slfw

    * Create an ISO. I used the following command:

    mkisofs -hfs -part -map ./boot.list -no-desktop \
    -hfs-volid "iMac DV Rescue CD" -hfs-bless ./cd_contents/boot \
    -r -o slfw.iso ./cd_contents

    That should do it! Of course, when I actually acquire a broken iMac DV, I will be able to say that with more confidence... :-)

  3. #3
    Welcome to Mac-Forums, camateg! A pretty cool idea you have!

  4. #4

    Member Since
    Jan 02, 2007
    I hope that someone will find it useful, including me!

    I won my eBay auction for the "broken" iMac DV last night ($5.50!!!) and it is being shipped today, so we will see! Also, I will make adjustments to my CD as needed.

    If this works, it will sure beat tearing the whole machine apart to bypass the video, in a worst case scenario!


  5. #5
    One thing that I would like to mention is this: those old gumdrop iMacs had a notorious weakness with the analog board. This weakness was carried over the first two generations of eMacs as well.

    The analog board frying prevents any start up from happening so there is a nuance here that I hope anyone searching for this understands. If it is the analog board going belly up, the only thing to do is changing it.

    This has happened to me with a grape iMac, btw. The replacement cost was quite prohibitive for me (the repair shop asked over $400CAN to replace the part) so I opted in buying a brand new iMac G4 at the time.

  6. #6

    Member Since
    Apr 25, 2006
    Yeah, but nowadays you can get that analog board on Ebay for next to nothing, just install it yourself.

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