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Old Jul 18, 2006, 01:52 PM   #1
Peel
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Continuous Reboot Loop

I went to wake my iMac G5 this morning, and soon after hitting the space bar it rebooted. The screen went gray, the apple came up, the process disk started spinning just as usual. Then when the screen was turning to my blue desktop I heard a slight *pop* or *click* sound and it robooted again. Then the process repeats itself - over and over. It happens at exactly the same place every time - it gets to the part where the desktop is about to come up (the blue starts to draw from the top, and gets about 3/4 of the way down the screen), and then *click* reboot.

I've tried starting in safe mode, and starting from the Tiger install disk. In both cases the same results.

Any thoughts? Is my computer fried?
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Old Jul 18, 2006, 02:29 PM   #2
funkychunkz
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Quote:
Originally Posted by Peel
I went to wake my iMac G5 this morning, and soon after hitting the space bar it rebooted. The screen went gray, the apple came up, the process disk started spinning just as usual. Then when the screen was turning to my blue desktop I heard a slight *pop* or *click* sound and it robooted again. Then the process repeats itself - over and over. It happens at exactly the same place every time - it gets to the part where the desktop is about to come up (the blue starts to draw from the top, and gets about 3/4 of the way down the screen), and then *click* reboot.

I've tried starting in safe mode, and starting from the Tiger install disk. In both cases the same results.

Any thoughts? Is my computer fried?
Do you have any peripherals attached? If so remove them, even keyboard and mouse. Is your RAM good?
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Old Jul 18, 2006, 02:48 PM   #3
OutThere
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Corrupted log-in item? If you're comfortable with single user mode you could see what is in your log in items folder from there, and delete it.
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Old Jul 18, 2006, 02:57 PM   #4
Peel
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Quote:
Originally Posted by funkychunkz
Do you have any peripherals attached? If so remove them, even keyboard and mouse. Is your RAM good?
No peripherals attached, and I've never had RAM problems before. Not sure how to go about checking that.

Quote:
Originally Posted by OutThere
Corrupted log-in item? If you're comfortable with single user mode you could see what is in your log in items folder from there, and delete it.
Actually no I can't. The point is that I can't boot in ANY mode: single user, safe, from CD...
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Old Jul 18, 2006, 03:02 PM   #5
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It wouldn't be a log-in item unless you have it set to auto log you in. Those can be bypassed by holding option, or shift (I forget) right before you log in.

In any case it's not that, because the problem persists in safe boot , and from a DVD. Does it actually start into those modes, or does it ignore you? Does verbose mode work?
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Old Jul 18, 2006, 03:06 PM   #6
OutThere
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Quote:
Originally Posted by Peel
Actually no I can't. The point is that I can't boot in ANY mode: single user, safe, from CD...
You didn't mention that you had tried to start in single user mode in your first post...


Anyway, because it doesn't boot from the CD (which I missed), it won't be a login item.

Have you tried zapping the PRAM?

http://guides.macrumors.com/Zapping_The_PRAM
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Old Jul 18, 2006, 03:15 PM   #7
Peel
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I'll give the PRAM reset a try when I get home. I'm wondering if this may be related to the Rev A video/power problem which is covered under repair extension. There is always a distinct *pop* whenever it get to the point when the screen is redrawing. This would be the point when any screen resolution changes would be taking place (going from splash screen to desktop) and I wonder if that's where the problem lies. I'll have to check with my Apple store, as this extension is good for 2 years from purchase.
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Old Jul 18, 2006, 08:11 PM   #8
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Quote:
Originally Posted by Peel
I'll give the PRAM reset a try when I get home.
Good luck with the computer responding to the keys
No seriously, good luck.
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Old Jul 19, 2006, 02:28 PM   #9
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Well reseting the PRAM didn't do it, nor did opening the cover and reseting the SMU. So I made an appointment and took it in to the Genius Bar at my local Apple Store. They diagnosed the problem as being a power supply failure.

The cure?
Replace the power supply AND the logic board.

Cost to do so?
$935.75

But since this is covered under the extended repair warranty, the cost to me was $0

The guy said it would take 5-7 business days to get it fixed, dependant on how many repairs were in line in front of me, and it looked like there were quite a few. So I went home, and less than an hour after my Genius Bar appointment, I received a phone call that the repairs were done, and ready to pick up.

Way to go Apple! I've never experienced this kind of turn around in service.

So everything's up and running like normal now.
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Old Dec 3, 2008, 08:08 PM   #10
AlecR
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I had the same problem as Peel, i.e., continuous reboot. However, when I started to follow the steps implied by the thread (reset the SMU, etc.) using the instructions at this link:

http://support.apple.com/kb/HT2173

my iMac started up fine when I had the back cover off and power reconnected. I didn't have to do anything past Step 7. The only other thing I'd done is blow a little dust out of the inside, after I'd opened it. The iMac is now up and running like a champ again.

So, knock on wood, no hardware failure.

Hope this helps someone ...
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