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Old IMAC Screen Problem

2046 Views 13 Replies Latest reply: Apr 21, 2012 1:49 PM by u2canfreefall RSS
u2canfreefall Calculating status...
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Apr 15, 2012 11:03 AM

I bought an IMAC  (old snow ball desk top) years ago and never had any problems with the machine.  The other day I was working on it and left the room and came back hours later.  The machine had gone to sleep with the small white light in the lower right corner.  I tapped the keyboard and it would not wake up so I held the power button in and turned it off.  Today I turned it on and I thought the screen flickered and the machine sounded like it booted up, but the screen is black.  Any suggestions?

iBook / iMac, Mac OS X (10.3)
  • Kenichi Watanabe Level 7 Level 7 (30,005 points)
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    Apr 15, 2012 11:52 AM (in response to u2canfreefall)

    The first thing you can try it to unplug it from power for about 15 minutes (or longer), then connect it back and try to start it up.  When you connect it, if you have been using an old (or overcrowded) power strip (surge suppressor), try connecting it directly to the wall outlet.  Also, initially press the power button with only the power cable connected; disconnect all other peripherals.

  • Jeff Level 6 Level 6 (11,160 points)
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    Apr 15, 2012 8:26 PM (in response to u2canfreefall)

    It could be that the PAV (Power-Analog-Video) board has gone bad (a common failure in those old iMacs), which would leave you with a darkened screen.  If this is the case, I'd pull the hard drive and retire the computer.  It's a dangerous repair for someone to attempt who isn't experienced with CRT-type TV repair, because of the danger of severe electrical shock.  Because that part is now-discontinued, I wouldn't pay for professional installation of a used part with unknown mileage and equally unknown remaining service life.  In six months, you could be in the same situation.

  • Kenichi Watanabe Level 7 Level 7 (30,005 points)
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    Apr 15, 2012 10:21 PM (in response to u2canfreefall)

    You described it as "old snow ball desk top."  I was thinking it was a white slot-loader iMac G3 (with a CRT display).  But I just realized that could describe the dome-shaped iMac G4 that has its LCD display on an "arm."


    So, can you clarify which model iMac you have?  This list may help to identify the exact model.


  • Kenichi Watanabe Level 7 Level 7 (30,005 points)
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    Apr 16, 2012 6:02 AM (in response to u2canfreefall)

    You can try resetting the PMU (power management), following this procedure



    Other possibilities - The Mac performs a hardware test at startup.  A component, such as the power supply, may not be passing the test, so the startup does not proceed.


    A dead or weak PRAM battery can cause startup problems.  The procedure to replace the PRAM battery can be found here (select your particular iMac G4 model)



    The PRAM battery looks like this



    Does it sound like the iMac is starting up completely and running, with the display dark?  OR does it not start up beyond a certain point?  If it seems to startup and run, with a dark display, the iMac's backlighting for the LCD may have gone bad. 

  • Kenichi Watanabe Level 7 Level 7 (30,005 points)
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    Apr 16, 2012 2:22 PM (in response to u2canfreefall)

    Since the battery has never been changed, it is probably weak or dead.  But that may OR may not be the cause of your immediate problem. 

    Still the light siver gray screen.

    Does that mean the screen is lighting up?  In a darkened room, does the screen obviously light up from behind?  If it does, the problem may not be the screen.

  • Kenichi Watanabe Level 7 Level 7 (30,005 points)
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    Apr 20, 2012 8:09 PM (in response to u2canfreefall)

    It sounds like the iMac is working as a computer, but the screen is not working.  I asked about whether the screen was still being backlit previously.  I asked because, if the screen is not working only due to the backlighting not being ON, that might (?) be an easiler (less costly) fix.  At the place where you entered your user name and password "blind," shine a bright flashlight on the screen.  Do you see anything being displayed on the screen?


    If the backlighting is working, but nothing appears on the screen (except the "silver gray"), then it is more likely to be a problem that is not worth the cost of repair.  That would be unfortunate, because that 20" iMac G4 is cool looking.


    You don't have the "mini-VGA to VGA" adapter, do you?  If you did, plus an old VGA external display, you could connect it and confirm that it is still working (minus LCD).  That port is supposed to mirror the built-in display.


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