[hart]

So, I've been trying everything I could think of with this machine and no results. I have a late 2008 24" iMac which won't get past the grey startup screen with dark grey apple. From there it goes to kernel panic message.

Just as a note I have put back in the original memory from Apple and am using a wired Apple keyboard for troubleshooting.

When I attempt start up from the install disk using C I still get kernel panic. I actually didn't realize this was possible.

When I start up using Option and choose the install disk as boot disk I still get kernel panic.

I can start up in target disk mode from another computer and access all my files and folders. I also used Disk Utility to run a repair while in target disk mode. And it's annoying as hell getting the install disk to pop up all nice and usable on the other computer in target disk mode but not being able to access it in the intended way.

I can start up using D and ran hardware tests and no trouble was found. Wouldn't any problems with the memory be reported in this test?

I have a full Timemachine backup just waiting to be used but I can't get to a junction where I can use it.

Is there any way to utilize the Timemachine backup while in target disk mode? Any other suggestions for work-arounds that might enable me to either start up from the install disk or get the backup onto the machine?


This is making me crazy having all the tools and not getting them to work together.

[hart]

Oh, follow-up thought: what about using Disk Utility in target disk mode and erasing the drive and starting fresh? Are there any pitfalls in this approach? I now actually have three copies of my data outside the malfunctioning machine as I used Timemachine to transfer everything to a new imac, kept the original Timemachine data and started up a NEW Timemachine backup for that second computer.

[chefpastry]

In my opinion, it definitely sounds like a hardware issue (think logic board, CPU, GPU, or RAM). I suggest bringing it to an Apple Store to let them have a look at it.

[hart]

I just do not have the $$ for that.

So stuff could be missed by the hardware test? That's disappointing.

[kido331]

a couple of things you could try.

1). shutdown the machine and leave it off for about 20 minutes and then see if it gets any further in the boot up process. if it does then you have a heat issue so you would then make sure the inside of the machine is not dusty and that it has good ventilation.

2). try removing all peripherals. use just a keyboard and try plugging it in to a different usb port. see if that helps.

3). try re-installing the ram modules. if that doesn't help, try removing the ram modules or replacing them.

if all these fail, then you are probably dealing with a bad motherboard and are out of luck.

[seanc]

Just to expand on point 2 of kido331s post, remove one or the other RAM module, then test.
You could have a bad slot.

[hart]

Can I make the angry face now?

Going to retry doing all possible combinations of memory and slots to make sure I've covered it but I think I've reached the end of the line. Guess I should look on this as a learning experience.

Grrr. Argh.

So question: are there things that the hardware test would miss? Seems kind of inefficient.

[AKcrab]

The hardware test can miss all kinds of stuff.

The hardware test that Apple provides is not the same hardware test they would use in an Apple Store.

[Spheric Harlot]

The Apple Service diagnostic also doesn't catch everything. RAM, it's fairly good at. But with the interface chipsets, it usually only checks that they're ready and available.

If your S-ATA port is defective, ASD probably won't catch it.

[AKcrab]

Originally Posted by Spheric Harlot 

The Apple Service diagnostic also doesn't catch everything.

So true.

(Apple's latest blanket diagnostic is the biggest waste of time ever.)

[Waragainstsleep]

Apple higher tier support is always requesting engineers use AHT over ASD when they have a problem they can't diagnose. I think the difference is that ASD covers multiple machines and AHT sometimes has extra model-specific tests (but not many of them).

That said, the thing about diagnosing a computer is that if it fails a test, you probably just found the fault (Not always but usually). If it doesn't fail the test, it could still have a fault.

Neither ASD or AHT will test the power supply and beyond a surface scan they aren't great at diagnosing hard drive faults either.

RAM, CPU and GPU are still the most likely I'm afraid. Outside chance of a weird PSU issue.

[P]

Originally Posted by Waragainstsleep 

Neither ASD or AHT will test the power supply and beyond a surface scan they aren't great at diagnosing hard drive faults either.

Correct, and I never understood why. Checking the PSU should be easy (every PC motherboard ever can report the voltages delivered to it from the PSU - if they're out of spec, bam) and given that it's a frequently failing part, adding such a test should be top priority.

[hart]

I guess I'm due for a hardware issue. The last hardware problem I had was a CD tray malfunctioning on a lime green ibook so suppose I shouldn't complain too much. It's just aggravating. Not to mention the $$.

Thanks guys for the insight into the next level up of computer troubleshooting.

[hart]

So, I made my very first visit to talk to a Mac Genius which was entertaining in it's own right. His conclusion is it's either the video card or logic board. Estimated cost of repair $600-1000. Even if we estimate a hundred or so reduction from going to a local guy it's still nothing to sneeze at.

A machine from the same era on the refurb page is $999 so it makes the repair look a little unreasonable. I suppose if I put in a lower quality video card it could be less, if it IS the video card.

I think I'll make the angry face a few times as this means I have to continue to share my computer with my son DestructoBoy.