Intel iMac Powering Down after Startup

[Mal]

I have an 24" Intel iMac (White) that is powering down about 10-15 seconds after turning it on. It chimes, the screen comes on and displays the Apple logo, then the whole thing shuts off. I checked the LEDs under the bezel, and the trickle power LED stays on the whole time, and all the other 3 come on until the point where it shuts down, then they go off as well. I'm guessing that the power supply or the logic board is bad, but anyone know how to check which it is without simply getting a replacement power supply? Is there a pin check I can do to see if the power supply is working?

jW

 

[rolex54]

the power supply would seem like the most logical choice
i think all you can do is buy one, try it out and if it doesnt work return it

 

[techie4life]

I have a 20" 2.4 that did this exact same thing. I took it to the store, where the genius diagnosed the problem, saying that it was most likely the logic board. A few days later, the store calls me and says that all they had to do was repair the disk permissions by booting up from an external disk. Hopefully that's your problem too....

 

[ArtTechFreak]

We had a white iMac do the exact same thing. I opened it up , and found that it had the bulging capacitor problem. It turns out that the machine was indeed in the group of machines that had bad logic board caps. We called tech support and they contacted Customer Relations since our machine was a few months outside of the extended repair period that was set up by Apple. Customer Relations referred us to the local Apple store. The logic board and power supply were replaced for free!

You may want to inspect your machine for the bulging cap issue. If it has the bulging cap problem, go to the Apple website and find if your machine falls into the affected serial number group. If it does, call tech support and get them to contact/escalate the issue to Customer Relations. CR is the group that gets the repair done for free.

 

[UncleRichard]

Same problem?

I am running 10.5.2 on an early 2006 1.86GHz Intel Core Duo 17" iMac (white), 160GB HD, 8x Superdrive, 2x1GB RAM.
1MB L2 Cache (from memory), bus speed 667 MHz (also from memory).
Latest BootROM (forget which one), checked for updates about a week ago.

Am, or rather was. It died this afternoon. I came back to it after lunch and the hard disk was making a distinctive pattern of clicks - a slow 1 - 2 - 3, which sounded like regular clicks and releases of a button, and then a short burst, followed by the 1 - 2 - 3 etc. The noises themselves weren't unusual, sounding just like ordinary disk access sounds, it was just the regular pattern that was distinctive, and the fact that none of my open apps were responding. I had been copying some files to the computer over the network and the copy had errored out with only a few files left to copy. Over the next 30-45 minutes I managed to force quit all the apps (about 7mins per program), but still couldn't shut down or restart, and ended up holding down the power button to switch the machine off.

I gave it half and hour's rest and powered it up, but it got stuck after the apple logo and the circle of spinning bars appeared (they were both still there). The hard disk made the distinctive pattern of sounds again.

The next time I started it, I tried zapping the PRAM, but the machine got to the same stage before powering itself down. Trying to boot into Safe mode or from my Leopard install DVD or in Target Disk Mode also failed. Every time, the Apple logo and the spinning circle of bars appeared, then the machine shut off, I presume before it can do any of those tasks.

I have tried taking each of the RAM modules out - same result.

I am not sure whether the problem is the hard disk, or the logic board or power supply, or something else entirely. I can't find the page on Apple's web site where you check your serial number to find if your machine has faulty caps (search terms were intel imac logic board faulty capacitors power supply serial number, and variations thereof).

Recently I have installed several freeware and shareware apps from magazine DVDs, and had particular problems with Intego Fileguard. It creates 'safes' to encrypt folders you specify, though when I asked it to put my emails, pictures, movies and music in four separate safes they all became corrupted immediately. In the case of the pictures and music I lost most of the files (nearly all recoverable from backups/original CDs, thankfully!).

Also, just yesterday the machine had crashed after a restart, reaching the same point as it does now, but this time it didn't power off. When I powered it down and gave it a rest, it started up normally.