iMac G4 root problem

Discussion in 'PowerPC Macs' started by reddrag0n, Jul 27, 2011.

  1. macrumors 6502

    reddrag0n

    Joined:
    Oct 1, 2007
    Location:
    Canada
    #1
    I was wondering if anyone could tell me what my poor iMac is doing.

    I bought it off of Kijiji and when it was demo'd before i bought it, it was working fine. Once i got it home and turned it on, i got this on my screen...

    [​IMG]

    I turned it off, let it sit overnight, and then turned it on again. This time instead of those lines, it fades from black to green then to a bright white.

    I am able to turn up and down the brightness via the keyboard *F14 and F15 keys* but that's all i can do. I don't see anything on the screen other than bright white.

    Is this a problem with the onboard graphics, or is it something else?
     
  2. macrumors 6502a

    btbrossard

    Joined:
    Oct 25, 2008
    Location:
    Chicagoland
    #2
    Can you hook up an external monitor to the mini vga port?

    Most likely, the on board video is bad, but hooking up an external monitor will confirm that for you (and rule out just a bad lcd display/video cable/ect).
     
  3. macrumors 6502a

    Joined:
    Apr 2, 2007
    #3
    Is it possible to test it on an external monitor? That way if it displays fine on the external monitor it's most likely a loose connector or possibly the LCD itself.

    If it doesn't display ok then it's graphic card related.

    Edit - Beat by a minute..
     
  4. thread starter macrumors 6502

    reddrag0n

    Joined:
    Oct 1, 2007
    Location:
    Canada
    #4
    Sure, if you can loan me an adapter to test that theory. since all the stores here in Edmonton don't carry the mini-vga to vga adapter.
     
  5. macrumors 68000

    Nameci

    Joined:
    Oct 29, 2010
    Location:
    The Philippines...
    #5
    could be the lvds cable... imo.
     
  6. macrumors P6

    Intell

    Joined:
    Jan 24, 2010
    Location:
    Inside
    #6
    A test of this is to move the screen around when its on. Do the images change when the screen is moved?
     
  7. macrumors 68020

    Jethryn Freyman

    Joined:
    Aug 9, 2007
    Location:
    Australia
    #7
    Can't really say either way here...

    You'd really need to find a mini VGA adapter to hook up an external display.
     
  8. thread starter macrumors 6502

    reddrag0n

    Joined:
    Oct 1, 2007
    Location:
    Canada
    #8
    Intell: As for moving the screen, yes, tilted it, moved it up and down, almost broke the neck because i moved it around so much, and no, still the same issue

    Nameci: Would that be the cable labeled TMDS?
     
  9. macrumors P6

    Intell

    Joined:
    Jan 24, 2010
    Location:
    Inside
    #9
    Yes, the internal video cable on G4 iMacs is called the TMDS cable. If the on screen images didn't change, then that cable probably isn't to blame.
     
  10. thread starter macrumors 6502

    reddrag0n

    Joined:
    Oct 1, 2007
    Location:
    Canada
    #10
    I have read on some of the apple forums that the inverter board might be to blame, but it still has brightness control. I have ripped apart the lcd unit and found 4 cables that connect to the inner area.
    1 - TMDS cable, 2 - the mic cable, 3 - the power light cable, 4 - both inverter power cables. I double checked all of those and still no change. So far it's boiling down to one thing, the logicboard. If i replace this, can i also go a step up in cpu speed too? Am not sure if the 700 and 800 MHz models were identical for those years.
     
  11. macrumors P6

    Intell

    Joined:
    Jan 24, 2010
    Location:
    Inside
    #11
    The 700 and 800Mhz boards are the same, but are different from the 1 and 1.25Ghz boards.
     
  12. thread starter macrumors 6502

    reddrag0n

    Joined:
    Oct 1, 2007
    Location:
    Canada
    #12
    Ok, so i can easily get an 800 MHz iMac G4 board with the onboard Geforce 2 MX graphics. That's good to hear.

    I just restarted the iMac and the same thing with the display is happening again. The fading from black to green then to a bright white.

    I will post a few videos showing that it works, but not the screen.
     
  13. thread starter macrumors 6502

    reddrag0n

    Joined:
    Oct 1, 2007
    Location:
    Canada
  14. thread starter macrumors 6502

    reddrag0n

    Joined:
    Oct 1, 2007
    Location:
    Canada
    #14
    Well, the iMac is running, updated to the latest 10.4.11 via VNC and now this is what i am seeing on the screen. It looks like girl stripes!!!

    [​IMG]

    Yeah, i think the graphics chip has given up the ghost
     
  15. macrumors 6502a

    btbrossard

    Joined:
    Oct 25, 2008
    Location:
    Chicagoland
    #15
    It's pretty...
     
  16. macrumors P6

    Intell

    Joined:
    Jan 24, 2010
    Location:
    Inside
    #16
    Trippy. If you can get that to move, I can get you to groove...
     

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