Any advice on reviving an iMac that stalls on bootup?

June 14, 2006 1:14 PM

Any advice on reviving an iMac that stalls on bootup? I hit the knowledge base, chatted with a tech, ran various tests and tried the basic tricks, but still, no go.

I'm not a Mac/OSX expert, but knew well enough to tap the Apple knowledge base (I reset the SMU, zapped PRAM, attempted a safe mode boot), chatted live with an Apple tech named Farida with a moderate grasp of English (we used the install disk to verify the disk, then run the extended hardware test, which took an hour, during which the tech abandoned me!), and I ultimately left my iMac "booting" overnight in the hopes that it'd eventually come through... but still, no go.

I have a 17" iMac G5 (Ambient Light Sensor). Basically, I get the startup chord, the Apple logo, then the spinning pinwheel... and that's it. The pinwheel spins and spins and spins, and nothing else. Nothing immediately preceded this problem... the iMac worked fine in the morning, I shut down, went to work, but when I came home, nothing.

Again, the basic tests/tools on the install disk seem to have found nothing. It's not a "forbidden symbol" or question mark or sad Mac... it just hangs at the Apple logo and pinwheel. (Hence the inability to boot in "safe mode," since I'd have to get past that step to see any indication that it took.) The tech suspected memory, since I upgraded from 1GB/512MB to 1GB/1GB a few weeks ago, but the iMac worked fine every day since then, until yesterday. I even went back to the original memory chips as part of my troubleshooting, with no change. And ultimately the memory passed the hardware test.

Any likely culprits? Corrupted OS, disk, or some unidentified hardware issue? Any advice? I'm guessing that my next step is pestering someone at the Genius Bar, but in case there are slightly more advanced tricks ("Hold down the command and 'V' key while reciting Vogon poetry!") I should try, I thought I'd tap the hive mind.

posted by pzarquon to computers & internet (11 comments total)

Actually, you SHOULD hold down command-V while booting, to go into verbose boot mode. This will show you more details about what's going on, instead of the spinner. You may see something suggestive in there...
posted by xil at 1:23 PM on June 14, 2006

the 17" iMacs had a problem with bulging capacitors and bad power supplies. Google iMac G5 and capacitor to find out more. You should be able to make a case for this to be repaired for free if the unit is out of warranty.
posted by Gungho at 1:36 PM on June 14, 2006

Actually, I got the unit in July of last year (so it's still under the original warranty) and I also got the extended support plan... so according to Apple's website, I've got about 720 days left. If other geek tricks don't work, I'm figuring I might as well make use of a service I've paid for.

Knock on wood, I've almost never had to tap Apple for support... so I'm curious, if a little hesitant. Too many bad experiences with other PC repairs that my instinct is to fix it myself!

Thanks for the 'verbose mode' tip, Xil. I remember coming across that (along with 'single user mode') in my KB scans, but don't think I actually tried it.
posted by pzarquon at 1:40 PM on June 14, 2006

It's possible (if your Mac had the power plug pulled or other sudden power loss) that your directory data got fried, as it may have been writing that data at the time. This has happened to me a couple of times in the past, in the midsts of some over-zealous dusting of the power strip and the inadvertent flipping of a switch. My solution, after the same amount of fiddling as you seem to have done, was to purchase DiskWarrior, boot from that disk and rebuild the iMac Hard Drive's directory. The only difference in my situation is that I have an 20" iMac, but it was purchased around the same time as yours.

It has worked for me on more than a couple of occassions, and besides, DiskWarrior is worth its weight in gold as an indispensable Mac troubleshooting tool.
posted by DannyUKNYC at 2:07 PM on June 14, 2006

Have you tried booting from a CD/DVD? If so, can you see your hard drive?
I second DiskWarrior, it's the only Mac drive utility that's worth a shit.
posted by doctor_negative at 2:14 PM on June 14, 2006

One word, and the folks above have already said it:

DiskWarrior.

Having worked as an Apple Authorised Service Provider in the past, I swear by it.

Get DiskWarrior by hook or by crook, boot from the CD, run it, then your Mac will almost certainly boot again.
posted by armoured-ant at 4:20 PM on June 14, 2006

Open up the iMac (as you have upgraded the ram, this should be old hat).

With the top of system facing away from you, look down towards the bottom at the capacitors. If they are laying flush, you are ok, but if they are bulging or oozing brown fluids, bring your mac in for service. Also look around the power supply, it is on the very bottom of the unit, where the wires come out and go up to the motherboard, look for grey / brown smoke damage, and see if you can smell if something has burnt. Again, bring it in to be serviced.

The big issue is that the failing capacitors in the iMac G5's can cause a myriad of problems, so my standard operating procedure for supporting them (and i've had 4 go bad this last month from various clients) is to check the capacitors before doing anything else.

Apple has an REA out on these units, so even if it is out of warranty, it will be fixed, if it is the capacitors causing the problem.
posted by mrzarquon at 4:38 PM on June 14, 2006

Thanks, everyone. DiskWarrior is the first thing I'll download when I get home. The second thing I'll do is get back in the habit of doing full backups (though I always backup critical stuff daily). I have four working Dell PCs doing nothing, they might as well be 'network storage'! May even use this as an excuse to play with Ubuntu...

The good news is, a Genius at the Ala Moana Apple Store got my iMac working. The bad news is, his shift ended before I returned, so I don't know what was wrong. The solution was an 'archive/install,' I guess an upgrade to OSX from a FireWire drive, but the problem? Who knows. Probably something DiskWarrior would have fixed though, I gather!

By the by, the first thing he did was pop the case open. "Looking for bad capacitors?" I asked. "You know it," he said. I guess for iMacs of a certain vintage, that's problem number one.

He did say he doubted my RAM upgrade was to blame... it could have been just about anything else. I'll put it back tonight -- after the backups.

By the by... "mrzarquon"? Pleased to meet you!
posted by pzarquon at 6:01 PM on June 14, 2006

Since the machine booted on the Tools disk, I would have made the bet that it was directory damage. A boot with cmd-s (single user) and FSCK might have repaired it.
posted by filmgeek at 6:24 PM on June 14, 2006

eh, archive & install is the first thing they always make you do at the genius bar. it means to run the installer disc, but use the option that just archives your old system files and installs the OS again. usually you also give the option to preserve all the user accounts as well, or you end up with the equivalent of a factory-fresh mac...

if you want to know if your memory is good, download memtestosx, boot into single user mode (apple-S during boot) and run the memtest program (if you installed it in /Applications, then type "/Applications/memtest/memtest" (no quotes) at the prompt) and let it run for a while. it will exhaustively test your memory and you'll know for sure if you have a bad dimm.
posted by joeblough at 11:46 PM on June 14, 2006

I suspect that the boot sector on the drive is corrupt. That doesn't happen often, but may not be easy/possible to fix.

So, take another mac, a laptop, perhaps, connect both computers with a firewire cable, and boot your iMac holding down the "T" key - into target disc mode. Then, copy over your important files.

After you're done, reformat the HD, reinstall the OS, and you should be fine.
posted by cptnrandy at 5:51 AM on June 15, 2006