Capturing cause of sporadic iMac restarts

Question

One of our iMacs began auto restarting at random (?) times yesterday. It looks like it might be a loss of power but none of the other 4 Macs on the same circuit are restarting so if it is power it must (?) be internal.
Is there a log I can look at to see if it shows any system crashes or other indications of what is going on ?
I've run "repair permissions" and am about to also run "repair disk"
Hardware Overview:
Machine Model: PowerMac8,2
CPU Type: PowerPC G5 (3.0)
Number Of CPUs: 1
CPU Speed: 2 GHz
L2 Cache (per CPU): 512 KB
Memory: 2 GB
Bus Speed: 667 MHz
Boot ROM Version: 5.2.5f1
Serial Number: W8532*T9U
System Software Overview:
System Version: Mac OS X 10.4.11 (8S165)
Kernel Version: Darwin 8.11.0
Thanks,
-Sven
<edited by host>

Answer 1

Hi
Launch Console which you will find in /Applications/Utilities. Clicking on the Logs icon will show you two logs: console.log and system.log. The sysem.log logs everything that is going on. Below these two logs you will see references to other logs. Clicking on the disclosure triangle for ~/Library/Logs will reveal the CrashReporter log. In there you should find logs for anything that may have caused your imac to crash, be it an application, a driver, or an obscure hardware fault. Below ~/Library/Logs you should see /Library/Logs. Clicking on the disclosure triangle for this should reveal archived logs.
Random crashes can sometimes be caused by drive/directory issues or even simply reinstalling a clean OS can occasionally cure problems.
Hope this helps, Tony