Sense Check on hardware problem

[jpadie]

I have an iMac early 2008 intel 24in.
I moved office over the weekend and now I find that after two years' service the iMac is playing up.
It will only sporadically boot from the hard drive. and when it does boot the OS is very non-responsive. In the background I can hear the drive constantly spinning up and down.
On its own I would ordinarily swap out the hard drive and see whether that makes a difference. It _feels_ like a drive problem and it is possible that a knock whilst travelling from one office to another has hurt the drive head.
HOWEVER I want to be a bit more certain as taking an iMac to bits is non-trivial. and there is a second symptom that is also present which makes me wonder:
the iMac will equally only sporadically boot from the installation DVD.
I thought that it might be that the installation media was scratched or otherwise compromised, so I tried a freshly purchased Snow Leopard disk to the same result. It's just not booting. Sometimes stuck on the cog wheel and sometimes stuck on just a grey screen - no apple logo.
i have reset the pRom. I have tried safe booting and get the useless kernel panic message telling me that it cannot find the ACPI kext. I say useless because that does not tell me what is wrong, since the symptom appears in DVD boot and hard drive boot.
sporadically I do succeed in booting from the DVD. and when I do I have tried to repair the hard drive. this runs successfully and no errors are reported. So I try to reinstall the OS but the drive does not appear in the installable locations.

By sporadically, by the way, I mean once in every 50 or 60 attempts. There is no discernible pattern to successful boots.

As said, it sounds like the hard drive is constantly powering up and down and _some_ reads are clearly successful. I suspect a damaged SATA controller on the drive but, as said, I would very much like corroboration before I give up a day to rebuilding the machine.

thanks
Justin

 

[jmgalvin]

Since you're having problems booting from both the hard drive and the dvd, it would appear to be something other than a hard drive problem.

If you have 2 ram modules, you might try taking out one and see what happens. Then put it back in and take out the other. That's one way of seeing if you have a bad ram module.

Also, did you move the machine yourself? If not, it's possible that the thing got dropped or otherwise damaged in handling.

Using OSX 10.3.9 & 10.4.11 on a G4, G5 & Intel Macbook

 

[SYQUEST]

Have you used Disk Utility?

You might open Console and read some of the log messages. OS 10 talks to itself all the time, and I am sure there will be lots of clues there...

....JIM....

 

[jpadie]

SYQUEST
yes. when i have been able to boot to the installation DVD i have used disk utility to fix the drive. no faults are reported.

I have been unsuccessful at booting to either the HD or the DVD since posting.

When I am in the DVD install boot, I have not been able to get to the logs as the HDD was not mountable.

@jmgalvin
It was me that moved it. Although I did so late at night I am certain that I gave it no hard knocks. the road is a little bumpy in places but nothing untoward.

I will try the RAM swap out but I suspect I would be getting different behaviours.

I am very much hoping you are wrong about it not being the hard drive as that would lead either to a power controller failure or to a fault in the SATA controller. which I cannot face doing myself.

 

[fisheromacse]

I would tend to agree with Syquest, it sounds like it could be either loose RAM or bad RAM.

I had one stick go bad in an eMac with nearly identical symptoms as yours. I removed the RAM 1 at a time and it booted fine with just 1 of the 2 in, but when swapped around it failed to boot...a good excuse for me to upgrade my RAM to the max for that old machine, which BTW is still getting daily use.

 

[jpadie]

I'm pleased to report that it was just the hard drive that was fubar. the RAM is fine.

replacing that was, in fact easier than I anticipated although, of course, despite taking every care in the world, a screen screw went missing during the rebuild.

the imac now sports a 1TB western digital caviar green drive and is whisper quiet (even quieter than before) and now sports a clean install of snow leopard.

i can only assume that the constant spin up/down of the hard drive was confusing the imac and therefore not allowing a boot from cd.