iMac G5 works in Safe Boot mode, freezes otherwise

[bytowne]

Hello! My 5-year old iMac G5 (2 GHZ Power PC, 1.5 GB Ram, non-iSight 20" model) started freezing on Thursday. First freeze was upon waking up from sleep. Re-boots freeze on startup, but at different points in the process, but almost always after successfully getting at least as far as showing my wallpaper image.

Sometimes, the spinning beach ball of death prevents anything at all from loading. Other times, everything looks like a successful start-up, mouse moves around screen, but no application will respond.

Have run disk utility. Hard drive seems fine; disk permissions had lots of troubles but have been fixed, apparently successfully. SMART status has been verified.

I've re-installed the OS, which means 10.5.8 that was running has now been replaced with 10.5.1 from the original disks. Same symptoms.

Some programs were set to start up on Login, and several freezes seemed to happen just as Suitcase Fusion 2 or Skype or Safari were 'dancing' to indicate that they were starting up. Turned off that feature for each program involved and iMac still freezes, either before or during any attempt to launch a program. It even will freeze when opening something very simple like Address Book.

Through all this, I can reliably get the iMac working with a Safe Boot, and programs work fine in this mode. But every attempt to boot up 'normally' meets with failure at some point in the process.

Any ideas? Thanks for your help.

[hughvane]

Freezing can be caused by faulty RAM, or boot sectors of the hard drive. Both can only be evaluated with Disk Utility from the Install disk.

Seeing you have the original Leopard disk, boot from that and run Disk Utility > First Aid > Verify Disk, and then repair if necessary.

Don't rely too much on permissions repair from the installed Disk Utility. A better job is done by OnyX Titanium's Software • Download.

If you should get the iMac booting 'normally', then there is a little utility that will check the status of installed RAM, Memtest Memtest OS X.

[bytowne]

Thanks. I had run Disk Utility, but not from original disks. Meanwhile, I took it in to an authorized Mac shop and they are stumped. They have switched out the RAM and have eliminated that as the culprit. The only other theory they have is that the new (well, not new, actually refurbished) logic board that they installed in Jan. 2010 has some suspicious looking capacitors. Can the logic board be at fault if everything is working okay in Safe mode?

[hughvane]

The only other theory they have is ... the logic board that they installed in Jan. 2010 has some suspicious looking capacitors. Can the logic board be at fault if everything is working okay in Safe mode?

Absolutely!!! If the capacitors are bulging, or worse still, leaking, then the logic board needs replacing - pronto! Hopefully the replacement job done earlier is covered by warranty.

[bytowne]

Sadly, the logic board was covered by a 90 day warranty and is now about 6 months old. I never would have agreed to the new logic board had I known it was refurbished rather than factory new, but the Mac dealer in question says that he told me. I think I'm out of luck here. Thanks for your help with this.

[hughvane]

Don't despair. Because of the outrageous cost of a new logic board (and refurbished ones aren't too cheap either I gather), seek out your nearest electronic repair shop to find someone who's prepared to solder in new capacitors. They cost about US$1 each I believe. A number of M-F members have had logic boards repaired this way.

If you're prepared and feel confident to remove and replace the logic board yourself, you'll save considerable labour costs. There are manuals and online video instructions on opening up an iMac.