G4 cube woes

Discussion in 'PowerPC Macs' started by HunterZ, Dec 11, 2018.

  1. HunterZ macrumors newbie

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    #1
    Found my wife's G4 cube in the garage the other day and booted it up. It worked fine, except that the PRAM battery must have been dead because it had forgotten the time.

    I then rebooted it and the screen wouldn't come back on. The screen's power light is solid amber, and I can hear the HDD when I turn it on, indicating that it is probably booting. I tried connecting a monitor to the VGA port, but that didn't work either.

    I replaced the PRAM battery with a fresh one and hit the PMU reset button under the GPU, but it didn't help. The power supply status LED inside the G4 cube is green. There is another LED next to the RAM that is red.

    Any ideas? Thanks.
     
  2. captainfamicom macrumors member

    captainfamicom

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    #2
    Test the GPU in another PowerMac. Maybe it failed or some caps blew?
     
  3. HunterZ thread starter macrumors newbie

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    #3
    The only other Apple computers around are laptops, so that's not an option.

    I tried re-seating the GPU (including disconnecting and reconnecting the AGP riser from the GPU) and the RAM, along with another PMU reset, but no change.
     
  4. captainfamicom macrumors member

    captainfamicom

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    #4
    Turn it on with the top off and feel the heatsink of the GPU. After about 30 seconds does it start to warm up? I did this in an old HP computer with a failing GPU. If it doesn't get warm, the GPU may have failed, or something on the AGP bus is messed up.
     
  5. HunterZ thread starter macrumors newbie

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    #5
    The GPU heatsink does get warm.

    However, now that I have it open it looks like the DC-to-DC board status LED may actually be yellow instead of green.
     
  6. captainfamicom macrumors member

    captainfamicom

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    #6
    You might want to look on the DC board and see if anything has blown or corroded. If it hasn't, then it COULD be the CPU (don't quote me on that, I haven't worked on a Cube in a while).
     
  7. HunterZ thread starter macrumors newbie

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    #7
    I'm actually more concerned about the DS2 light being red (is that normal?)

    After looking at the service manual, I measured J3 on the video riser with a multimeter and am getting 27.5V. This is within the 27-28.5V tolerance specified by the manual. I think this means that power is OK.
     
  8. captainfamicom macrumors member

    captainfamicom

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    #8
    If you have any spare RAM, try slotting it in. (PC-100/133) It could mean a bad stick of RAM.
     
  9. HunterZ thread starter macrumors newbie

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    #9
    Does standard PC RAM work in the G4 cube, or does it require something special? I'm sure I have some Pentium II/III era PC100/PC133 RAM lying around somewhere.

    Edit: I'm not sure if it's the RAM, though. I think the service manual said that it tests RAM on boot and will flash the power light if there's a problem.
     
  10. AphoticD macrumors 68000

    AphoticD

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    #10
    Just to eliminate the GPU, can you hear it booting off the hard drive if you remove the graphics card? Does it chime at all?

    I don’t own a Cube, but my understanding is that most non-registered PC133 DIMMs will work.
     
  11. HunterZ thread starter macrumors newbie

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    #11
    I can hear the HDD going for a minute or two after power on, even with the GPU installed, so I think it's booting.

    I don't think it has built-in sound. It flashes the power LED if there are problems, and I'm not seeing flashes. I could try plugging the USB speakers in, but I'm not sure that they'd be active at boot time.
     
  12. AphoticD macrumors 68000

    AphoticD

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    #12
    Ok, I would recommend you try a different graphics card.

    Not to totally steer you away from buying another similar card, but to perhaps shed some light on things - from my experience (and this might be mine alone), the ADC power draw on these old cards appears to put added stress on the aging GPU components. Of my half a dozen or so AGP Mac graphics cards, only the two which I ran using the ADC port have failed on me.

    Perhaps someone like @bunnspecial could chime in on this - any recommendations for the OP?
     
  13. HunterZ thread starter macrumors newbie

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    #13
    I guess the thing to do then would be to find my old PC Geforce 2MX and flash it to a Mac-compatible firmware, then swap it for the Rage 128 Pro.

    We mostly just want to get some files off of it, though, so we're going to try putting it in target drive mode first in case that works without the GPU.
     
  14. AphoticD macrumors 68000

    AphoticD

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    #14
    Firewire TDM should work fine without a working GPU.
     

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13 December 11, 2018