mini-ITX powered grape iMac

Discussion in 'Buying Tips and Advice' started by FerrisWorld, Oct 10, 2009.

  1. FerrisWorld macrumors newbie

    Joined:
    Aug 6, 2002
    Location:
    America
    #1
    How reliable are new analog/video boards or flyback transformers when you replace them on tray loading iMacs?

    Here's why I want to know:

    I've been wanting to try this project for a while, and finally started it. I have a Grape iMac 333Mhz, and I'm attempting to replace only the motherboard, hard drive and optical drive, while keeping the original crt screen, and power supply. Following some guides to install iMac motherboards in ATX cases, I was able to make a wiring harness that will adapt the iMac's power supply connector to a 24 pin ATX power supply connector, and it worked! Initially I tried with an Intel d945gclf2d, which is a dual core atom 330, with the 945gc chipset, but it wouldn't power on all the way. Using MacTracker, I discovered the the power supply in these is only 80 watts, so I tried the new Asus at3n7a-i, which is the same cpu, but with the nvidia ion chipset, which uses much less power than the 945gc. This board fires up just fine using the iMac's original power supply! Unfortunately, I wasn't able to get anything on the iMac's screen.

    Before even buying a motherboard, I had tested the iMac's screen by hooking up a hd15 to db15 adapter that had come with an old mac radeon that I bought, connected to the vga out on my Lime iMac DV. It worked the first time, but then in later tests, I noticed a lot of flickering, and large black areas. I thought (hoped) that it was just the db15 extension cable I was using, but now the iMac will not display any video at all. I even tried putting it back together with it's original motherboard. I'm almost certain it's the flyback transformer from reading all kinds of information online, but I don't know if it's worth fixing for a couple of reasons. I suspect that even though I could get video from the vga out on the iMac DV, I still won't be able to get it from the itx board or any other vga output except one from an iMac G3. I suspect this because I could still get output from the iMac DV, even after I got no video from the itx board (I know the itx board works because I connected it to another screen). My other concern is that if I fix it, and I AM able to get the vga out on the itx board to drive the iMac's screen, that it will somehow over stress the flyback transformer and cause it to fail again soon after the repair.

    Anyway, I was really excited and somewhat surprised that my wiring harness actually worked to power on the itx motherboard, but it was frustrating when the flyback transformer went out. Maybe something I did caused it. Probably.

    I may end up trying this on a slot loading model in the end. If I fabricate a frame that mounts the motherboard under the optical drive (it will fit), and the hard drive in the back, I think it will work. They also have more power (150w) and more reliable flyback transformers. The wiring will be a nightmare, but I think I can handle it. The pinouts are well documented.

    If anyone can advise me on whether it should be possible to drive the crt with the itx board, and on the flyback transformer repair, I would really appreciate it. I found an article on how to do it, including precautions regarding discharging the crt etc, so I don't need advice there, just on its reliability.

    Also, please refrain from comments about how stupid this might be etc, or why don't you just do this instead. I really want a flavored iMac with an intel itx board inside of it okay? And no lcd swaps, I don't like the way they look. I would be willing to spend money repairing the flyback transformer if I thought it was going to hold up and actually work with the motherboard. Am I going to run Windows? No, I'm going to use hackintosh patches and run Snow Leopard.
     
  2. goMac macrumors 603

    Joined:
    Apr 15, 2004
    #2
    This is stupid, why don't you do something else instead...

    :p

    Actually, this sounds really cool. I don't have any ideas, but I want to see how it turns out.
     
  3. Theclamshell macrumors 68030

    Joined:
    Mar 2, 2009
    #3
    ill be honest in saying i dident understand half of what you just said :D

    this sounds like a sick mod though and if you end up getting it working post pics and vids because i would want to see this

    good luck and just be careful with the crt
     
  4. FerrisWorld thread starter macrumors newbie

    Joined:
    Aug 6, 2002
    Location:
    America
    #4
    Is there another place I should post this where more knowledgeable people might see it? No offense.
     
  5. goMac macrumors 603

    Joined:
    Apr 15, 2004
    #5
    Actually, I kind of thought this would be the place, but most of the newbies who hang out here are probably mostly post-Intel people and never operated on the insides of a machine that old. :)

    As a Mac tech I used to work on the insides of those iMacs, but I wouldn't have any idea of where to start with what you're doing...
     
  6. FerrisWorld thread starter macrumors newbie

    Joined:
    Aug 6, 2002
    Location:
    America
    #6
    Did you have to replace a lot of analog boards?
     
  7. Dr.Pants macrumors 65816

    Dr.Pants

    Joined:
    Jan 8, 2009
    #7
    I would have posted something this complex in the eMac forum. [H]ardforum would be more geared towards this sort of thing, but their Apple forum is nowhere near as complex as anything I've seen here (might have to post in the Power Supply, Motherboard, or Display forums).
     
  8. Consultant macrumors G5

    Consultant

    Joined:
    Jun 27, 2007
    #8
  9. FerrisWorld thread starter macrumors newbie

    Joined:
    Aug 6, 2002
    Location:
    America
    #9
    I figured it out on the grape tray loader!!! I happened to find a post on applefritter.com in which someone was asking about doing it on a slot loader, and someone mentioned that the crts in all crt iMac's are of a fixed horizontal frequency design, which is why there is only one refresh rate per resolution. Well, I don't know if I already posted this, but I was trying this on my slot loader with a custom video adapter cable I made using from pinouts that I found, but it didn't work on there. So then I hooked up a PowerBook G4 to the grape's monitor, set it to 1024x768@75, and it worked! I thought it was broken! Just to be sure, I also hooked up a Toshiba Tecra with windows xp, and it also worked on that setting! So I guess as long as I feed it that resolution, or 640x480@117, and 800x600@95, I should be fine. It doesn't seem like OS X or windows will support those two without some third party apps since they don't detect them automatically, but I think I will only want to use 1024 anyway. This means that to see the bios post screen, I will have to connect another monitor, but once I'm done setting up the bios and stuff, I won't need that. It also means that you won't see the bios screen in normal opperation, you'll just see when the OS starts to load, which will make the iMac appear stock until you realize it's got Snow Leopard. Wooo!!
     
  10. megapixel86 macrumors newbie

    Joined:
    Jun 20, 2010
    #10
    Hey FerrisWorld,

    I hate to dredge up old topics, but how did this project turn out for you. I tried contacting you directly, but your profile doesn't have any contact info. I'm EXTREMELY interested in doing the very thing you are doing. I had a blueberry given to me last week and immediately the idea of putting an atom board in it starting swirling in my brain. The truth of the matter is, I lack a large bit of technical knowledge, and I'm not sure where to even start. I've built too many pc's to count, but I've never even opened up this blueberry. Is there anyway that you can help me get started on this project? You mentioned some tutorials, where did you find those?

    Thanks!
     
  11. ottomobille macrumors newbie

    Joined:
    Apr 18, 2010
    #11
    i used to work on those all the time back when i was 7 or 8 i still have a couple of them in my basement. i used to have a 266 with a 6 gb hdd and recently was using it for a moniter for my ibook. btw im 15 now.
     

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