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Old Feb 6, 2011, 04:02 PM   #1
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Unhappy iMac G5 - Black screen and loud fan noise upon boot

Right here it goes, my iMac's had this problem for a while now where if you were to turn it off for the night and you came back to turn it on it would stick to a blank screen, no disc noise and some loud fan whirring after a few minutes, but if I were to wait half an hour and reboot it, it would boot normally and go straight into Leopard. It never really bothered me before, but now this is getting beyond a joke since I'm selling it soon to get a MacBook and I want to solve this problem once and for all. Anyone mind helping me here?
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Old Feb 6, 2011, 05:01 PM   #2
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sounds like a soon failing harddrive if there are no other abnormalities , but on a g5 its always worth to check the capacitors anyway and to change the harddrive you have to open the iMac anyway , a good time to clean it inside too, but just another question i guess you did pram reset, permissions repair already or? and does it still remember the date and time?as of the age its due for a new pram battery too
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Last edited by MacHamster68; Feb 6, 2011 at 05:09 PM.
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Old Feb 7, 2011, 09:01 AM   #3
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Which G5 is causing the problems, the 1.8 GHz or the isight? The 1.8 is much more susceptible to the bad caps issue (and also a bad power supply issue), so it's worthing inspection the logic board.

MacHam's suggestions are all good ones. The only thing I'd advise is to check the RAM as well. I was having problems that were mis-diagnosed as a failing logic board (an Apple genius and a 3rd-party tech both got it wrong). Turned out it was bad 3rd party RAM. I put the original Apple RAM in the machine and the problems went away. Sent the RAM back to the manufacturer, got a new kit, and it's been running fine since. The symptoms I was having are similar to the ones you describe. Might be worth checking out if you have other RAM you can swap in.
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Old Feb 7, 2011, 07:00 PM   #4
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I think the failing to wake up from sleep with a black screen is PSU related or the infamous bad cap issue. If you are good at soldering, the cap kit can be purchased for less than $20.

Have you ever noticed any lines on the screen or weird artifacts showing up? The other known issue with the G5 iMacs are the graphics cards. This requires re-flowing the solder or buying a entire new logic board.
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