Imac g3 from CRT to LCD

Discussion in 'PowerPC Macs' started by coquito_x, Sep 10, 2015.

  1. coquito_x macrumors newbie

    coquito_x

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    #1
    printf ("Hello world! \n");

    This is my very first thread at all, please contact me if there is any rule I infringe or if this is not the place for this kind of question.

    I'm sure this is not the first and will not be the last time that somebody asks this:

    How can I replace the CRT monitor of an old Imac G3 (M5521) with an LCD one?? without several modifications specifically, replacing the power supply as shown here:

    http://www.mactech.com/2005/09/01/eyemac-g3-lcd

    I got here by looking at this previous thread:

    http://forums.macrumors.com/threads/imac-g3-lcd-conversion.450143/

    The last post (#10) leads to a "blank" link so I haven't found how to do what this member explains.

    A complete and detailed "cookbook" procedure is most appreciated if there exists. Any other guide is also welcome.

    Thank you all for your attention.

    P. D. Please, I would really appreciate you to keep comments such as "why would you want to do that?" or "vintage macs remain classic with OEM hardware" or any other similar sentences that won't give me a solution. Thanks again.
     
  2. MacCubed macrumors 68000

    MacCubed

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    #2
    I don't think you can, the only way would be to find a monitor that uses the same pin layout
     
  3. happyfrappy macrumors 6502

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    Location eh?
    #3
    It depends upon the model iMac, 233-333Mhz tray-loader models would need an Apple monitor to VGA converter adapter which is a simple mod via using any VESA mount friendly 15" monitor with its own power supply--removing the CRT won't disable the iMac.

    Slot-Loaders were much more tricky as certain models(DV/DV+) had VGA mirroring which is a do-able modification looping a VGA cable out the bottom while wiring up a dummy monitor dongle inside from the former built-in monitor wiring(aka headless dongle/resistor to fake a working signal so the mirroring VGA port works at boot). Now if the slot-loader lacks the VGA mirror port, you'll have to research the pin layout or experiment with a spare monitor... chances are that thread/post 10 likely had that info. Tearing apart CRT AIO Macs are a safety hazard which likely scared most users from modding them.
     
  4. coquito_x thread starter macrumors newbie

    coquito_x

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    #4



    Thank you very much for being so specific happyfrappy.

    Yes, it (the imac g3) is a slot-loader and it does have a VGA port under a plastic cover beneath the far end of the case. That dongle/resistor you mention how does it work?? I think I require to make a patch to make the main board work along with the new monitor (LCD) and without the old CRT and without changing the power supply, am I right?? So where do you recommend me to start looking for it??

    Thank you in advance, your reply was really insightful.
     
  5. bunnspecial macrumors 603

    bunnspecial

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    Kentucky
    #5
    Granted it's on a totally different scale, but I replaced the CRT in a Classic II a couple of days ago. Unlike iMacs, the CRT is right there when you open up the computer, and it's also a significantly smaller(and easier to handle) CRT.

    With that said, you can minimize the safety hazards of dealing with CRTs by discharging them before you mess with them. To do this, you locate the anode-which looks like a big suction on the side of tube-and stick a grounded screwdriver under it. Letting the computer sit a week or two is also a good idea.

    I've actually used external monitors on tray loaders for diagnostic purposes. I've always plugged a multi-scan DB-15 Apple CRT directly into the port, but using a DB-15 to VGA dongle should be possible.

    All of that said, I'd encourage you to leave the CRT. Even though it's shadow mask, it's still a nice quality tube and looks great at its max resolution(1024x768 off the top of my head). iMac G3s are some of my preferred systems for playing old OS 9 games, and the CRT has a big advantage in this department since you can gracefully run 640x480 full screen games at a reasonable size. LCDs tend to look pretty crummy if you down-res them, especially this much.
     
  6. coquito_x thread starter macrumors newbie

    coquito_x

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    #6


    Hello bunnspecial, thank you for your advise, I appreciate it.

    Yes, you are absolutely right by highlighting the smooth change in the resolution of CRTs compared with LCDs that will only look fine if they display at native resolution. However, I have to confess this machine is not for me but for my daughter. For that reason I don't want her to receive that radiation from old CRTs, not to mention the waste of energy and the heavy weight.

    Do you know where can I find a schematic or something that gives me some light in this personal goal?? The challenge is to keep everything (speakers, main board, DVD/HD and power supplies) inside but the CRT, neck, flyback, etc, etc... and replace them with the LCD. The machine is an Imac G3@600 MHz (I think), slot, and has a VGA port beneath it. Above, happyfrappy wrote that I require a wiring up a dummy monitor dongle inside from the former built-in monitor wiring(aka headless dongle/resistor to fake a working signal so the mirroring VGA port works at boot)... Do you know where to look for it??

    Thank you for your reply.

     
  7. happyfrappy macrumors 6502

    Joined:
    Oct 14, 2007
    Location:
    Location eh?
    #7
    As much as the iMacs keep the CRT safely out of the way, display repair/replacement/LCD conversion opens up the risk of electrical shock.

    I only own a tray-loader, afterwards I was mainly using PowerBook G4s.

    As far as dongle/resistor you'll want to research "headless" PC server/displayless laptop, its simple way to trick the graphics chipset into thinking there is a monitor that isn't there if you unplug the built-in CRT/display connection--slotloaders won't boot via external VGA unless the internal monitor is working.
    I found this site which explains the internal display pinout of the iMac Slot-Loader, looks like you can make a VGA breakout board/cable patch: http://www.cryogenius.com/hardware/imac/
    Just incase that website ever goes offline, I'll repost the pin out:
    VGA to iMac
    1 red video --- 17
    2 green video --- 15
    3 blue video --- 13
    5 gnd --- 3
    6 red rtn --- 18
    7 green rtn --- 16
    8 blue rtn --- 14
    10 gnd --- 3
    12 S data --- 1
    13 hsync --- 9
    14 vsync --- 11
    15 S clock --- 2

    From http://pascal.monte.free.fr/imac/video.html, pins from little white
    14-pin connector on video board end of salvaged video cable to VGA connector:
    1 black SCL to VGA pin 15
    3 yellow SDA to VGA pin 12
    4 white vsync to VGA pin 14
    6 blk/wt hsync to VGA pin 13
    2 org ground to VGA pins 5 and 10
    11 grn Power On to power board's signal inverter

    This is the only Apple iMac Slot-Loader service PDF I could find online: http://www.scribd.com/doc/103447/iMac-G3-Disassembly-Guide

    This forum may have been the ATX conversion idea, while some links are "dead/broken" the idea of a conversion patch/bridgeboard or iServer conversion discussion: http://www.applefritter.com/node/9274
     
  8. weckart macrumors 68040

    Joined:
    Nov 7, 2004
    #8
    I would have thought the eMac might be a better candidate for a flat screen LCD replacement purely on the basis of fit. The bowed bezel of the iMac G3 to accommodate the very curved CRT is going to make any LCD look a bit odd.
     
  9. coquito_x thread starter macrumors newbie

    coquito_x

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    #9
    I'm sorry I didn't thank you the other day, but thank you, this gives me more light.
     

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