Intermittent Symptoms, faulty powersupply?

[notquitefob]

Hi,

I've been experiencing the following symptoms intermittently over the past several months. I am out of apple care since early 2009 and could use some help narrowing down the root of the problem. I've already ran the Apple Hardware Diagnostics Extended Test with no problems reported.

Mac Pro 1,1 early 2006, 2x3.0Ghz(Woodcrest dual-core), 8gb ram, 8800gt, 2x750gb seagate and 2x320gseagate running 10.6.2


1. (Energy Saver configured to NOT turn off hard drives when not in use) Sometimes the computer will hang with the spinning mouse cursor while the hard drive appears to power off and back on. I have 4 drives in the computer in 2 raid(1) arrays, one OS, one Time Machine. Both arrays are healthy and have passed Drive Fitness tests. If I pull 2 of the 4 drives out, the symptom goes away.

EDIT: if problem persists, kernel panic comes shortly after. if the hard drive spins back up, everything goes back to normal until the next time the hard drives power off again. These are drives that past Seagate's own diagnostics utilities.

2. From a cold start, the computer sometimes will not start pushing the power button. Nothing spins up, but you get a single click as if it's working, but no fan and no hdd spool up and no video. If I wait a while and try again, it will work.

Probable causes: power supply and/or motherboard. Question is, how do I determine which before I buy a replacement part for the swap?

Any ideas?

 

[666sheep]

Tried PRAM and (or) SMC reset?

 

[notquitefob]

Tried PRAM and (or) SMC reset?

Tried PRAM, haven't tried SMC reset. I can't imagine this to be soft/firmware since it's so random and the symptoms range from not being able to power-on at all, to hard drives losing power while using the OS.

 

[666sheep]

Try SMC reset then. It's easiest what you can do, besides Apple recommends it in case of "power on" problems: http://support.apple.com/kb/HT3964 If it will not help = problem is hardware related and will be difficult to diagnose without spare parts.

 

[Spacedust]

Run this and post results: http://www.versiontracker.com/dyn/moreinfo/macosx/32454

 

[notquitefob]

Run this and post results: http://www.versiontracker.com/dyn/moreinfo/macosx/32454

I'm currently running just 2x750gb seagate drives in RAID1 configuration, which is also what my OS is running on. Both drives, and the combined RAID1 array reported no errors. Please let me know if there's anything specific I should run with the software.


UPDATE:


I recently replaced the PSU. I've also made sure disk sleep is completely disabled per the following command:

sudo pmset -a disksleep 0

I haven't had problems waking the machine from sleep, but unfortunately I'm still getting intermittent hdd spin down, which lasts ~ 15-30 seconds with the spinning wheel of death. DISK UTILITY claims my RAID1 array is in good shape and "ONLINE."

any ideas?