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  1. #1


    Member Since
    Mar 08, 2008
    Posts
    14
    Mac Pro Sudden Power Down
    Hey all!

    I need a bit of help identifying (and hopefully fixing) a problem with my Mac Pro (early 2008 model - pre Nehalem).

    I have run into a problem with my Mac Pro recently where it would just suddenly powers down, no kernal panics or warnings whatsoever, just as if someone unexpectedly disconnected the power completely at the mains. The strange thing is that the problem only occurs about 15-20 mins in when I run a 2 pass encoding session using Avidemux (version 2.5.4 - its been installed for a long while before the problem started). I use my computer for equally as intensive tasks including web/graphic design and flash animation (Creative Suite), sequencing with Logic running plenty of CPU intensive soft synths, and have not managed to replicate the problem (as of yet). I never encode a video if I have other processes running and leave only the Mac turned on when doing this (monitors etc are switched off).

    First thing I assumed is that the machine was overheating. Ruling out cleaning the inside of the case, which I do on a regular basis anyway, I set to acquire some fan/temperature monitoring software so I could actually see what was happening on the fly (iStat menus for checking temperature of components, and SMC Fan Control for altering fan speeds).

    With these installed, I first checked my system temperature. I assume its the overall temperature that is displayed in the menu bar at the top right of the screen, which is roughly between 30 - 35 degrees depending on room and general temp. I altered the fans to about half way dragging the little bar (for the CPU fan alone, this is like two thirds faster than default) and this got the system down to roughly 27 degrees give or take. Confident that the system was definitely cooler, I ran my test again and started to perform another 2 pass encoded video. Using the stats on the menu bar, I could see activity in the CPU log, which seemed normal (dont have the info to hand, but it appeared no more than 1/5 of total processing power - two quad cores on board).

    So far so good, nothing out of the ordinary. Then all of a sudden, bam! Power cut after about the 25 minute mark. The temperature was around 33 degrees when it happened.

    I have run the Apple hardware test on boot (both short and long tests - passed both) and sequentially had the machine on for an entire day over the weekend just gone (and it was quite a hot one here in the UK) with no sudden power outages whatsoever. The Mac is plugged into the same power strip as my two monitors, preamp for recording, and my speakers (2.1 each powered separately). When the power cuts on my Mac, the other devices remain on so I don't think it is a power overload (I've used this setup for a long while now with no problems).

    In fact, I can power up my Mac straight after this power cut and use it as normal until I run the process through Avidemux again.

    Does anyone have any ideas or suggestions what I can try next? Obviously iStat provides looooads of info on individual component temperatures and I guess any one of these MAY be the culprit, however I'm not too sure what I'm looking for - assuming it is an overheating issue. Maybe the power supply is on its way out? Would that account for this particular problem though, as I've only ever had the scenario in the past with PC power supplies outright dying and not "playing dead" so to speak.

    I will appreciate any advice anyone can give me on this.

    Thanks in advance!

    Matt

  2. #2

    harryb2448's Avatar
    Member Since
    Nov 28, 2007
    Location
    Nambucca Heads Australia
    Posts
    22,109
    Specs:
    Imac 27" Retina 5K, 512GB flash memory, 3.3GHz, 16GB memory, macOS Sierra beta.
    Are you running the Mac Pro through an UPS or surge protector? If so try without. and if not try another mains connection. If no joy perhaps the Power Supply is on the way out.
    Hang on to those original install discs like grim death! Using OS X.7 or later make a bootable USB thumb drive before running Installer!

  3. #3


    Member Since
    Mar 08, 2008
    Posts
    14
    Hi there,

    I'm running the Mac into a surge protector usually, however I have tried it plugged into different wall sockets directly and with different power cables to no avail.

    The situation changed the other day when I came home from work. I turned on the Mac and it got as far as the login screen. After about two minutes of being on the login screen (I didn't actually enter my details or touch anything at this stage) it just turned itself off randomly. Therefore, I don't think what I'm trying to do in Avidemux is totally to blame for the problem in this respect.

    After the Mac turned itself off this time, it wouldn't let me turn it back on for about 30 seconds of pressing the power button. When it finally started up again, it seemed to run fine for the rest of the evening.

    Does this sound like the power supply is on its way out or could it be something else? If I need a new power supply, will I need a specific type of power supply and not just a standard PC one?

    Any further help appreciated.

    Kind regards,

    Matt

  4. #4

    harryb2448's Avatar
    Member Since
    Nov 28, 2007
    Location
    Nambucca Heads Australia
    Posts
    22,109
    Specs:
    Imac 27" Retina 5K, 512GB flash memory, 3.3GHz, 16GB memory, macOS Sierra beta.
    Sounds like a failing power supply for sure. Usually about the $400 at an Apple repairer.
    Hang on to those original install discs like grim death! Using OS X.7 or later make a bootable USB thumb drive before running Installer!

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