06-03-2008, 08:54 AM

We have 24 iMacs in a computer lab. We came in one day after a thunderstorm and found 8 or so of the computers would not start up. They are all on power strips.

What I found to work is to unplug the power, click the power button repeatedly, replug in the computer, press and hold the power button. It takes about ten seconds. Then I hear the fan power up, hear a loud beep, and then the computer starts up normally.

Does anyone know why this happened? Any help would be great!

06-03-2008, 01:02 PM

Not sure what happened to the 8 machines but consider your computer lab to be extremely lucky not to have had any of the machines destroyed by lightning.

With that many iMacs it would pay for your lab to either use a three leg
combined lightning arrestor for incoming power or put the entire lab on a commercial UPS.

I have witnessed incidents here in Texas where nearby lightning strikes destroyed valuable electronic equipment during one of our fierce thunderstorms. Power strips, even those with built in surge protection will NOT protect equipment against lightning strikes that produce power spikes and surges.

Regards.

06-03-2008, 01:07 PM

Well when I mentioned that there was a thunder storm, I ment to get out that we lost power, not that there was a power spike. There have been one or two other times that we had the same non bootablitiy after just being shut down. We have looked into the UPS route but it is all more expensive than what we can currently purchase (the school district bought the computers for us, but we manage the rest).

06-03-2008, 06:14 PM

Have you tried resetting the PMU on the iMacs?

Here is a link to apple docs. on this:-

http://docs.info.apple.com/article.html?artnum=95165

01-16-2009, 11:48 AM

I work at at high school and our 20 inch, 2.8 GHz iMacs are having the same issue. Every few weeks approx. 1/3 to 1/4 of our iMacs, which are all hooked up to surge protectors, will not boot properly. Apple has been working on the case for almost 4 months now and unfortunately hasn't been able to come up with anything concrete.

The only way to get the macs to boot is to reset the PMU, which is done by unplugging the cord from the back of the computer, but it seems that the time required for the cord to be unplugged until the PMU resets is getting longer and longer Whereas inn the beginning of the school year a few seconds would do the trick, now often times we have to leave the cord unplugged for a few minutes for the Mac to reset itself.

We are in Florida, where it storms quite frequently,and never had issues of this sort with the Dell computers we had prior to Apple. This is definitely an Apple issue!!! It's about time they get this figured out!!