# Yet another iMac G4 flat panel boot-to-black



## cleal (Dec 31, 2007)

I've been using Macs since '85 and this one has me stumped.

Machine in a 800Mhz G4 15" flat panel with 512/60, Airport card and Superdrive. OS 10.4.11

Symptom: Boot to black screen most of the time. Workarounds that sometimes work:
1. Zap PRAM then try Option key and choose HD to boot.
2. Zap PRAM then use C key to boot off install disk.

Most of the time it's just a black screen.

Superdrive acts as it it's flakey as it doesn't spin up as normal sometimes.
I did get the Apple diagnostic disk to test OK and I used the Disk utility in the Tiger install disk to check the hard drive. It also passed with flying colors.

The battery registered 3.5v so I replaced it and did the thermal paste replenish plus push the reset button next to the Airport card.

I also wiped the drive and reinstalled Tiger and the latest combined updates. It rebooted OK on the first round and then didn't boot with the latest security update.

My only suspect is the Superdrive as when it doesn't boot, all I get is silence  other than a few clunks from the DVD drive, a Pioneer 104.

When it does boot, the screen is bright with not even a dead pixel.

Any insights welcome. Thanks!!


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## Soulwar (Dec 31, 2007)

First thing that comes to mind, with what you describe, it could be the logic board. It would explain why zapping pram sometimes works and the screen. It's possible it could be affecting the SuperDrive as well. Are there any firmware updates you can try?


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## cleal (Dec 31, 2007)

Soulwar said:


> Are there any firmware updates you can try?



This model 15" flat panel does not require firmware updates. Also, the two times I've been able to load and run the Apple hardware diagnostics, everything checks out fine.

In the early phases of the problem, the Superdrive became unavailable and not seen by System Profiler. A PRAM zap brought it back.

I've just seen a firmware update for the DVD drive at http://www.apple.com/support/downloads/imacsuperdriveupdate.html and I don't know if it's been applied yet so I'll try it as well. I don't rate this a high probability of fixing the problem though.

Thanks for the suggestions.


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## cleal (Dec 31, 2007)

DVD firmware upgrade didn't help. But I was able to boot using the zap PRAM, hold down Option key and then select HD.

Did a fix permissions and checked HD. Some permissions fixed but only by removing execute bit. Nothing unusual.

Log does look interesting. Note the intentional gap as this is boundry for end of failed boot and start of normal one.


_Dec 31 13:29:16 cleals-imac kernel[0]: Creating HFS+ Attribute B-tree File (504 nodes) on Macintosh HD
Dec 31 13:32:33 cleals-imac shutdown: reboot by cleal: 
Dec 31 13:32:34 cleals-imac SystemStarter[369]: authentication service (384) did not complete successfully

HARD RESTART

Dec 31 13:35:37 localhost kernel[0]: standard timeslicing quantum is 10000 us
Dec 31 13:35:37 localhost mDNSResponder-108.6 (Jul 19 2007 11: 33:32)[30]: starting
Dec 31 13:35:37 localhost kernel[0]: vm_page_bootstrap: 125326 free pages
Dec 31 13:35:37 localhost memberd[38]: memberd starting up
Dec 31 13:35:37 local_host kernel[0]: mig_table_max_displ = 70
Dec 31 13:35:37 localhost lookupd[41]: lookupd (version 369.5) starting - Mon Dec 31 13:35:37 2007[/I]

I'm wondering is the hang-up at starting *authentication service* is causing this?

It has to get network services from an Airport card logging into an edge router using WEP.


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## Soulwar (Dec 31, 2007)

Just a quick thought, are you able to boot in safe mode at all? Check this link for trying...
http://docs.info.apple.com/article.html?artnum=107392
 Let me know of the results?  I have a 17" iMac PPC G4 1GHz, so I am curios myself of what's going on...


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## CharlieJ (Dec 31, 2007)

Have you tried opening it? The cable's must be tiny. try looking at the connection. maybe it has broken. If its the logic board. Use it as a cool little server .


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## cleal (Dec 31, 2007)

Soulwar said:


> Just a quick thought, are you able to boot in safe mode at all? Check this link for trying...
> http://docs.info.apple.com/article.html?artnum=107392
> Let me know of the results?  I have a 17" iMac PPC G4 1GHz, so I am curios myself of what's going on...



Boot in safe mode? Not consistently. If it boots at all, it'll boot in every mode except open firmware. I've gotten the OF screen accidently once.

I don't think it's an inverter/backlight issue as the hardware tests OK, no sign of booting as evidenced by it being absent when I try to ping it or login via terminal or RDC.


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## Soulwar (Dec 31, 2007)

You can also try verbose mode. 
 Check link before starting...
http://docs.info.apple.com/article.html?artnum=106388
 It will allow it to display information on screen while it boots up.


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## cleal (Jan 1, 2008)

Soulwar said:


> You can also try verbose mode.



It won't boot up in either verbose or safe mode. It looks like booting up by using the Option key and selecting the HD is the only way to boot.

I think there is a hang up in the boot sequence as no log is written prior to a normal boot. Evidence of this is no entries with old dates after a zapped PRAM. All log entries have a current date after the network is up and it gets nntp to set the correct time.

It looks so far that I can get it to boot reliably by using the Option key method. Luckily this is a machine I paid $100 for and I intended to use it only as a thin client.

BTW, there really is a bug (real one but dead) below the main board as I can see it in the transparent area below the 2nd memory stick location. I've chosen not to take the board off the base in order to get it out because I don't have the heat transfer pads I need to install when putting it back together. I'd hate to think this is the culprit.


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## Soulwar (Jan 1, 2008)

Do you still have to zap pram every time before the "option" boot? Also, is the OS selected for the startup disk?
 The bug definitely could have done some damage. I've had equipment before that got fried due to some bugs.
It seems like the board is still the problem. Does it stay on after the boot? If so, just don't turn it off...


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## cleal (Jan 1, 2008)

Soulwar said:


> Do you still have to zap pram every time before the "option" boot?


No. After it wouldn't boot to safe or verbose mode I tried the Option key and it's worked 3 times in a row. Leaving well enough alone for now.


> Also, is the OS selected for the startup disk?


 Yes.


> It seems like the board is still the problem. Does it stay on after the boot? If so, just don't turn it off...



It stays on, goes to sleep as required, etc. Pending getting the thermal pads to remove the bug I will just leave it on. I'll update this thread if I ever do find out what is going on.

Thanks.


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