iMac stuck at grey screen after logo scn

J

jewcher

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iMac running 10.6.8 Snow Leopard that is stuck on the grey screen AFTER the logo screen. It will not go past that point unless you start it up in Target mode, and then select it as the startup disk from the connected computer.

I started by reseting the PRAM and NVRAM, then checked for hardware errors (with system disk and holding down the "D" at startup) with no results. I then started it up in Single User Mode and ran emergency disk repair mode, still with no results. I then started it up in Target mode, and it came up as an external hard drive on the working computer just fine. So I tried to start it up in target mode as the boot drive, and that was ok as well. I then restarted in target mode and from the working computer formatted the drive and reinstalled Snow Leopard, and nothing has changed. It still only boots through the Apple logo screen and then gets stuck on a grey screen (except for in target mode, where it seems to have no problems at all).

I was told that the computer was knocked and the power cable was yanked out while it was starting up, but never fell over. I assumed that it was a broken chain in the startup process, but it is still the same even after wipe and fresh install.

Any advice or diagnostic you can suggest would be helpful!
 
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Ok so this question is only a fraction of the whole conversation that I guess was turned into a thread.

So a real update is that my mini is back from repairs (DVD drive stopped working) and I am finally able to try and reinstall the system software into the iMac from the disk. Here is what happened:

So I started the (working) mini in Target mode and inserted the Snow Leopard disk. I then started the iMac (hold down option key) and selected the disk as the boot drive. Nothing happened except it got stuck on the Apple Logo screen.

Then I tried it again with the grey disk (that came with the iMac). It tried to boot into the disk, however during the Apple Logo screen, screen went dark and told me to restart.

So I was thinking motherboard? or RAM?

Thanks for the suggestion on trying one RAM module at a time, I hadn't thought of that...

As for reseating the ram... tried that tonight but same thing just happened....
 
So I tried both RAM individually in each slot, always ending in the same result, a kernel panic telling me I need to restart the computer during the apple logo screen. So I figure, either both RAM are bad, or the RAM isn't the problem....

Is there any way to test the logic board? I ran the Hardware test from the disk, but came back with an all clear.
 
I'd suspect the drive is the problem. Obviously the kernel panics happen when trying to boot from the drive. Could also just need a system reinstall?
 
I was thinking that all it needed was a fresh system reinstall, but I can't seem to figure out how to accomplish that.

So I get the same kernel panic when I try to start the iMac from the system disk in both the iMac's drive, or putting the mac mini in target mode, insert the disk, then try to boot the iMac from the disk from the mini drive (does that make sense??).

I can put the iMac in target mode to run through the mac mini, and have used this to reformate the HD and reinstall the OS, however, nothing changed. I was told that that will not load all of the drivers for the iMac and needed to do it the other way around, with the mini in target mode to get a proper install.....
 
(copied from a serial number decoding website)
Processor Memory Storage and Media
Processor speed: - 2.16 GHz
Processor Type: - Intel, Core 2 Duo (Merom)
Number of Cores: - 2
Bus Speed: - 667 MHz
Cache: - 4 MB L2 cache
64-bit Support: - Yes

Installed RAM: - 1 GB
Max. Amount: - 3.0 GB
Amount of Slots: - 2
RAM Speed: - 667 Mhz
RAM Type: - PC2-5300, DDR2, SO-DIMM.

Hard Drive: - 250 GB, 7200rpm.
Drive Bus: - Serial-ATA.
Optical Drive: - This unit has an 8x SuperDrive built in.
Optical Bus: - Ultra-ATA/100
Other Media: - None

Graphics Networking Ports and Expansion
Display Size: - 24-inch
Graphics Card: - NVIDIA GeForce 7300 GT
Card Memory: - 128 MB
 
I've been through these steps with fsck and nothing seemed to do much of anything. One strange thing was that sometimes it would come back with errors, and sometimes it wouldn't, even though I didn't change anything between runs.

I would start up in single user mode (which works for some reason), run it, and if it came up with an error, I would run it until it didn't (usually it came back clean on the second run). Then restart, but it still never made it past the grey screen after the Apple Logo screen.

I will try it again today just in case, but I don't think anything will change.
 
If the problem is just the hard drive then that would be great news! Sounds much cheaper to replace than the logic board lol...

But (maybe I am wrong in thinking this), if the problem is the hard drive, then how am I able to run Single User Mode? Or is that using data stored in some other part of the computer? For that matter, if the problem is the logic board how am I able to start up in single user mode? I would think the computer wouldnt do much of anything....
 
Hard drive can fail partially, so it's possible that the small size of the single-user boot is avoiding the bad sectors of the HD (not an expert on the single user mode bootup sequence, just my experience). Did you say you were still getting kernel panics booting from the install media?
 
So this should be everything:

When I try and boot like normal, it boots through the Apple Logo screen and then does nothing, perpetually stuck in a grey screen.

When I try to insert the install media into the computer and boot from the DVD (hold down C), I get a kernel panic telling me to restart.

When I put the iMac in target mode, then run it through my Mini (working), then I can access all of the data from the iMac through my mini. (I guess this is why I did not think it was the HD) (btw there is no data on the iMac except for system software)

So in order to install the system software onto the iMac properly (since I reformatted trying to fix it), I was told I needed to put my Mini in target mode, insert the installation disk, then boot from the iMac (option key) and select the disk. This also came up with a kernel panic. I had originally done this the other way around (iMac in target mode, then installed the system software through the Mini) but was told this would not work to get all the drivers needed to run independently.

I hope that all makes sense....
 
jewcher said:
So this should be everything:

When I try and boot like normal, it boots through the Apple Logo screen and then does nothing, perpetually stuck in a grey screen.

When I try to insert the install media into the computer and boot from the DVD (hold down C), I get a kernel panic telling me to restart.

When I put the iMac in target mode, then run it through my Mini (working), then I can access all of the data from the iMac through my mini. (I guess this is why I did not think it was the HD) (btw there is no data on the iMac except for system software)

So in order to install the system software onto the iMac properly (since I reformatted trying to fix it), I was told I needed to put my Mini in target mode, insert the installation disk, then boot from the iMac (option key) and select the disk. This also came up with a kernel panic. I had originally done this the other way around (iMac in target mode, then installed the system software through the Mini) but was told this would not work to get all the drivers needed to run independently.

I hope that all makes sense....
Click to expand...

In that case the HD is likely fine, as the install media should not require a working HD. Probably a RAM or logic board issue. It's a little strange that that booting from the HD is not causing a panic, though.

I would try resetting the SMU, PRAM, etc.
http://support.apple.com/kb/HT3964?viewlocale=en_US
PRAM: hold command - option - P - R on boot up.
(though there's not a lot of information to conclude that the PRAM or SMU is acting up, it's worth a shot as there's not a whole lot else you can try without replacing the HD)
 
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Yea I thought it was strange that it just does nothing and doesent go into kernel panic mode when you do a normal boot up myself... Why I originally thought it was just a bad command in the startup sequence.

I reset the PRAM, but nothing changed.... I also reseated the ram, and tried each ram chip individually (tho only 512MB each, so I wasent sure if one chip had enough power to start up the computer....) in each of the slots but that didn't get me anywhere either. What I did not do was try each RAM chip individually, and try to access the DVD install disk. Maybe one chip is bad and there is a bad startup sequence that wont let it start up even with the bad chip removed (assuming there is one.....)

Otherwise, I think I am giving up and calling it a logic board problem....
 
Hi,

Had a very similar problem when my mac stopped booting at grey screen and spinning wheel stopped.

After the initial boot the mac will try and switch the graphic card to graphics mode. If the graphics card is damaged then the mac will lock on the grey screen. Got a new graphics card and this solved the problem, if your graphics card is integrated onto motherboard (logic board) then you will need a new logic board.

Sometimes the graphics card will work in a low windows xp resolution mode, try installing windows xp and see how far you get.

Good luck.
 
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