Problem waking iMac from sleep

[HarmanyHank]

Hello:

My wife has a 20" iMac running Leopard which is now out of extended warranty. For the past few months, she has had problems waking the machine from sleep mode - on a intermittent basis. 

When the situation occurs, nothing she touches on the keyboard (or the mouse) will wake the computer from sleep mode. She has to hold the main power button for about 10 seconds and then push it again to get the machine to start up and boot up as if it had been completely shut down.

This occurs, as I said, intermittently - perhaps once or twice a week. It often, but not always, seems to occur after the computer has been on for a long time, such as 4-6 hours of continuous livestreaming of a radio station.

I have done some searching on the Internet about this problem but have found nothing satisfactory. I was told at one point by someone to occasionally shut down the computer and physically unplug the power cord and leave it for about 10 minutes before booting back up.  When I do this, it does seem to work (ie it will wake from sleep consistently) for a few days but then goes back to its intermittent habit.

There are peripherals attached to the machine (external hard drive, low power FM transmitter, printer, etc) but these have all been attached long before this problem stated to surface a few months ago.

If anyone has any ideas as to what I might try to alleviate this, I'd be happy to hear it.

Thanks,
Hank

[ben schmidt]

Couple of free things to try:

1) PRAM reset (unlikely to be related)

Resetting your Mac's PRAM and NVRAM
http://support.apple.com/kb/HT1379


2) If it's running Leopard (OS X 10.5), then download the last OS X 10.5 combo (not delta!) updater and apply:

Mac OS X 10.5.8 Combo Update, Aug 2009
http://support.apple.com/downloads/Mac_OS_X_10_5_8_Combo_Update

[HarmanyHank]

Thank you, Ben.  My wife is already running Leopard 10.5.8 on her machine so your second suggestion would not apply.

I've read a number of posts on line where people have tried the PRAM reset with no success, so I'm not inclined to try that.

She tells me that usually (but not always) when the computer has been on for more than about 2 hours, it won't wake from sleep the next time she tries to use it.

Thanks for your suggestions, nevertheless.

[ben schmidt]

A couple of clarifications:

My wife is already running Leopard 10.5.8 on her machine so your second suggestion would not apply.

The suggestion was not about ensuring your OS X 10.5 is at the latest revision level, although that is always good advice, and I can understand how it might have come across that way.

Rather the essence of the suggestion was about re-applying all of the OS X 10.5 revisions as a single update. Hence the emphasis on ensuring you downloaded the OS X 10.5 combo updater. Sometimes re-applying all the updates at once (which is what the combo updater does) can correct rare abnormal situations which develop over time as the individual OS X updates are applied incrementally, one-by-one as they are released by Apple.

I've read a number of posts on line where people have tried the PRAM reset with no success, so I'm not inclined to try that.

I share your skepticism in this case. But resetting the PRAM is something which only takes a moment, and will not harm your computer.  http://support.apple.com/kb/HT1379

[Dan Millar]

First of all, WHICH 20" iMac is it - G4, G5, or Intel?

For G4s and G5s PMU is the Power Management Unit, for intel iMacs (early 2006 and up), it is the SMC - System Management Controller - and resetting it is exactly the first thing you should do whenever there are concerns with the power system. The method depends on which model you have.

For earlier G4 and G5-based iMacs, resetting the PRAM(Parameter RAM) may also help. This is done by holding option+command+P+R immediately after starting up the iMac and holding them down until you hear a second set of "chimes" - the machine restarts and the PRAM is reset. Some techs will let this cycle repeat three times before being satisfied that it has taken effect - it can't hurt.

If you have an older 20-inch, pre 2006, then some disassembly is required to reset the PMU. Let us know if that is the case and we can point you in the right direction for instructions. Otherwise, resetting the PMU/SMC is pretty straightforward, but does depend on the model - so let us know which model you have and we can give you exact directions.

One other question - when the iMac refuses to wake up - is it in fact still powered up or has it shut down? One way to tell is to press the caps lock key - if it lights up - the mac is still on, otherwise it has no power and thats a different problem...

Happy Mac'ing!

Dan

[HarmanyHank]

Dan:

The computer is a 3-year-old Intel iMac.  I will try your suggestion to hit the caps lock key to determine the computer's status when it refuses to wake from sleep mode - the next time it happens, whenever that is - and let you know.

I will also try Ben's two suggestions.

Thanks to both of you for offering some ideas and clarifications. Stay tuned...

[Smashedbanana]

Check the circular vent hole at the rear under the aluminum stand. It gets clogged sometimes...

Ed

[HarmanyHank]

Dan:

This morning the Mac refused to wake up for the first time since my last post on March 6.  That was consistent with previous patterns because my wife had the computer running yesterday for a long stretch of time in one session (about 4 hours) - and it is usually after these long sessions that it refuses to wake from sleep.

So, I tried your suggestion and hit the caps lock key. It did not light up.

I don't know if that tells you anything, but there it is.

Hank

[Dan Millar]

Hey Hank,

That means the power is off, which could be one of two things.

• The computers Energy Saver preferences contains a "Schedule" setting for sleeping and powering on or off the computer at set times, and this has been set to power the computer off at a specific time - sometime overnight from the sound of it.
  
• The computer is overheating and shutting down on its own.
  

The first is easily fixed, just un-set the scheduled power-down.

The second is not so easy to fix, but as someone suggested, may be just a clogged vent causing the computer to slowly overheat and shut down. Left untreated, this will eventually kill the computer. It's highly unusual for a computer to overheat unless its airflow is severely impeded, so check and clear all vents, and that the fans are operating as expected. If your fans are dead, that may also cause this problem.

Although I don't recommend temperature monitoring for most users, you may find it useful to pick up iStat, a system monitoring widget, just to see if a) your temps are going out of control because b) your fans aren't spinning. Here's the URL:

http://www.islayer.com/apps/istatpro/

It would help us narrow down the problem/solution if we knew exactly which "three-year-old" imac you have - check the label for a product number, like the iMac 20-inch mid-2007 has an order number of MA878LL - every model is slightly different and has their own issues so narrowing it down will help us answer your questions.

Another thing that may help is to check your Console messages (/Apllications/Utilities/Console) at or around the time the Mac shut down. From the list on the left in the console window, chosse All Messages and scroll back to the time period before you rebooted the computer. The messages are somewhat cryptic, but you may see hints as to what is going on, i.e. "shutting down on SIGTERM from...".

Good luck and...

Happy Mac'ing!

Dan

[HarmanyHank]

Hi, Dan:

Thanks for continuing to take an interest in this strange tale of the sleeping iMac.

First:
The computer is scheduled to go to sleep every evening at a set time; often my wife is on the computer at that time and just overrides the sleep notice. I don't think this is the problem, otherwise it would be refusing to wake from sleep all the time. As you can see from my previous posts, the problem only happens very intermittently.

I could disable the sleep schedule and see what happens.  But this sleep schedule has been set ever since we've owned the computer, long before this waking problem surfaced.

Second:
It is very unlikely that the vents are blocked; I checked them as best I could. Besides the computer is completely free-standing with lots of air space around it.
The fan is working as it always has.

Third:
I'm not sure sure which product number you are referring to.  The BUILD # is 9L31a, the serial number is W88020UEX86 and the computer was purchased on February 6, 2008 from the Mac Group.  It's specs are: 2.4 GHz, 1 GB memory, 320 GB disk space, ATI Radeon HD 2600 PRO-256MB.

Now, for the interesting part.  I have never checked Console Messages before so I wasn't sure what to expect. I did what you said regarding displaying "All Messages" and all I see are messages from 27/08/09 thru 10/08/09.  Those are the only messages showing, nothing before that date and nothing after.  To me, that is totally bizarre.  (On my own iMac, these console messages go right up to the present, of course).  What do you make of this?

I can't remember when this waking problem first surfaced but I think it was some time early last year (in 2010).

That's my report for today.  And thanks again.

Hank

[Smashedbanana]

This fits the symptoms:

http://support.apple.com/kb/HT2166

However it you would have be applied it if you are doing all your software updates. Does this come up when you run software update?

Ed

[HarmanyHank]

Hello, Smashedbanana:

I just tried to install the graphics firmware update you suggested and I get a message saying that the computer does not need this update.

The waking problem is not related to running any specific program or file as far as I can tell.  The most common thread running through (almost) all the occasions when it has happened is that the computer has been put to sleep after a long session on-line.

Thanks for the thought.

Hank

[MacMoore]

How has "the computer been put to sleep" ?

Is it through Energy Saver-->Computer sleep slider setting?
Or by using the power button once the "Allow power button to put the computer to sleep" line has been checked in Energy Saver?
Or by a "Schedule..." sleep setting?
In Energy Saver, are the "Power" and "UPS" settings set to the same values?
In Energy Saver, have you tried to "Restore Defaults" ?

[HarmanyHank]

MacMoore:

The "Energy Saver" settings in Leopard are set as follows:

Under "Sleep":
"Put the computer to sleep when it is inactive..." for 1 hour
"Put the displays to sleep when the computer is inactive for ..." 40 minutes
(nothing else is checked)

Under "Options":

"Wake for Ehernet network administrator access" is checked
"Allow power button to sleep the computer" is checked
"Automatically reduce brightness of the display before display sleep" is checked
(nothing else is checked)

The scheduler is set up to put the computer to sleep every evening at 10:35 PM but often this is overridden because my wife is on the computer. She always actively puts the computer to sleep by clicking on the Apple icon and then clicking on"Sleep"

No, I have not tried to "Restore Defaults" since this problem surfaced, thinking it was not related in any way.  But I certainly could try that if there is a chance it might work.

Thanks,
Hank

[MacMoore]

I suspect the scheduler doesn't like being overridden by your wife, so it throws a tantrum.