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Thread: iMac weird colour screen & freezes on startup

  1. #1
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    Default iMac weird colour screen & freezes on startup

    Hi all!!

    I've encountered a problem with my 5 month old iMac 17" 1.25ghz, running Panther.

    I was using it fine, surfing away, doing nothing exciting, not installed anything recently, all of a sudden the screen colours changed (went pale magenta and cyan) and the cursor went all 'blocky'. It hadnt locked up completely, as i could still open the CD drive from the keyboard, and it would beep when I clicked in certain places.

    I held the power button for 5 or 6 seconds to restart it, and the familiar startup screen came up (i.e. Apple logo and the spinning 'pips') but the colour was still wishy washy (greyer, flickering, cyan and magenta). Then it would freeze up until restarted again.

    A few times it came up with a dialogue box in multiple languages saying the computer needed to be restarted by holding down the power button (which I was doing).

    A couple of times I managed to open the CD drive via the keyboard, and tried booting from the OSX Panther disc 1 (upgrade disc, does this have the same startup utilities on it??) but to no avail.

    I'm really struggling with this one!! Please help!!


    Thanks very much, it looks like a great forum here.






    *bookmarks forum to position in Safari bookmarks bar*

  2. #2
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    That doesn't sound like fun ;-(

    Have you been using ThermographX and Temperature Monitor? I would suspect heat as one possible cause. A loose connection somewhere as another. You are seeing a kernel panic on startup.

    Heat is hard on everything, disk drives especially. If you don't have a backup, you might want to make sure to have one. If there is a problem Disk Utility can't repair, Alsoft's Disk Warrior is best bet. The utilities on the Update CD is the same, it just means that doing an install requires there be OS X present.

    Any severe storms can put a strain on a system's power supply, too, if you don't have a UPS/line conditioner.

    Assuming you upgraded the RAM, RAM can always become a problem even if it allows you to work and runs for months - but least likely as you said you haven't done anything 'recently.'

    First thing I would try would be to hold down four keys to boot into Open Firmware, Command + Option + OF, then enter the following three lines:

    reset-nvram <return>
    set-defaults <return>
    reset-all <return>

    Which will then cause the system to reboot. This totally clears nvram so you will have to reselect the startup disk. So you might want to hold down the Option key to select a system, even if there is only the hard drive system 10.3.3. Or CD.... or... have your handy emergency backup FireWire drive that has a cloned backup of OS X on it also.

  3. #3
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    wow, thanks very much!!

    I'll print that out and give it a try when I get home.

    I havent touched anything on the mac since i got it, so theres no danger of anything being installed incorrectly.

    But it has been hot here for the last 3 days, and its suddenly dropped again, maybe something to do with that??

    I'll let u know tomorrow (I'm at work now.............)


    Thanks again.

  4. #4
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    Knowing how skimpy Apple is with default RAM and what is 'required' I'd look into adding more RAM. Your system will run much better, no matter what you use it for. 512MB PC2700 SO-DIMM $130 in the PowerBook, iBook SODIMM section for "USB 2.0 iMac."

    Summer heat has always been hard on iMacs. Having a G4 7455 1.25GHz in there only puts more heat in there.... assuming it still uses "passive" exhaust rather than fans.

    I remember getting a stereo shipped back from Far East with loose screws ;-)

    You can find those utilities I mentioned on www.macupdate.com or www.versiontracker.com - I would also recommend the recently updated Panther Cache Cleaner as very useful and handy utility. (A full discussion of utilities is in the OS X General Forum.)

    Having more RAM would be fun. Having a backup is one of those essential, non-negotiable items or eventualities.

  5. #5
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    TZ: The G4 imacs have a big, quiet, slow exhaust fan right at the top - around the monitor arm, and intake ports all around the bottom. Very similar to the fan at the back of the emacs, if you have seen one of them. Have not monitored temps, but looks like a pretty good system compared to the old fanless convection method.

    ali: The screen asking you to restart is a what you see when your OS has a kernal panic, which I guess you could just call a bad crash. Several things can cause panics, and bad memory is one of them.

    Follow TZ's reccommendations about backing up everything, then run Disk Warrior. Have you installed any software (or anything) lately? Anything you can undo or turn off?

    To open the CD drive, hold the mouse down during boot. even if the OS is dead, the tray should open. Insert the CD and close, then hold the C key down while you restart the machine, until you see the Apple logo (the logo loads when the machine has found an OS and is booting to it). As long as the CD is OK, and is Panther disk 1, and of coarse the CD ROM is functioning correctly, you should be good to go.

    If you had an external Firewire drive you could boot to that with a clean OS install to test, without touching your current OS/drive for the time being.

    If you back up everything, you can then erase the drive and reinstall everything from your restore disk. If the problem is solved you may never know the cause, other than the OS was not happy for some reason, but may be faster in the end that trying to fix it. Plus, you could spend countless hours trying, and it could be hardware all the while.

    If none of this helps and you thinks you are having a hardware problem, might as well get it looked at ASAP while under warranty. These little guys are hard to work on - kinda like a laptop - which usually means expensive, so don't put this off for months...
    "Imagine if every Thursday your shoes exploded if you tied them the usual way. This happens to us all the time with computers, and nobody thinks of complaining." -- Jef Raskin

  6. #6
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    Reminds me of some of the MacPlus "hoods" that added a fan on top. I wondered how long they could go fanless, especially when I saw some fried disk drives one summer.

    The iMac is obviously not a Mac I've been around much lately ;-(

  7. #7
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    Quote Originally Posted by TZ
    That doesn't sound like fun ;-(

    Have you been using ThermographX and Temperature Monitor? I would suspect heat as one possible cause. A loose connection somewhere as another. You are seeing a kernel panic on startup.

    Heat is hard on everything, disk drives especially. If you don't have a backup, you might want to make sure to have one. If there is a problem Disk Utility can't repair, Alsoft's Disk Warrior is best bet. The utilities on the Update CD is the same, it just means that doing an install requires there be OS X present.

    Any severe storms can put a strain on a system's power supply, too, if you don't have a UPS/line conditioner.

    Assuming you upgraded the RAM, RAM can always become a problem even if it allows you to work and runs for months - but least likely as you said you haven't done anything 'recently.'

    First thing I would try would be to hold down four keys to boot into Open Firmware, Command + Option + OF, then enter the following three lines:

    reset-nvram <return>
    set-defaults <return>
    reset-all <return>

    Which will then cause the system to reboot. This totally clears nvram so you will have to reselect the startup disk. So you might want to hold down the Option key to select a system, even if there is only the hard drive system 10.3.3. Or CD.... or... have your handy emergency backup FireWire drive that has a cloned backup of OS X on it also.



    Morning guys,

    boo hoo!!

    I downloaded the Temperature software, but the docs with it state that it doesnt work on a new iMac, but, it is in a very cool room, with lots of air round it so unless the fan is faulty, I dont think it would be a temperature thing. (Although I could be wrong!!)

    I can't remember downloading anything recently, I've been racking my brains backtracking but I'm positive nothing new has been added.

    I was just using safari and MSN Messenger at the time, if that narrows it down??

    I tried the Command + Option + OF, then enter the following three lines:

    reset-nvram <return>
    set-defaults <return>
    reset-all <return>

    and whilst the imac was in that mode, the screen was still 'distorted' (i.e. black lines running vertically every 10mm or so, breaking up the words. Although i could see that it said OK at the end of each line and it restarted as you described).

    I restarted and chose the Panther Upgrade disc 1 but still with the same results.

    It seems to go further through the starting up process if i hold the shift key down, but eventually still comes to a grinding halt.

    Typically, I've no backup, and my old iMac 233mhz is at a friends in a galaxy far, far away.

  8. #8
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    I restarted and chose the Panther Upgrade disc 1 but still with the same results.
    Ali, can you restart with the C key to the Panther 1 cd, then instead of installing- run a 'repair disk' on your startup disk using Disk Utility, which you open from the menubar? If you can and it finds errors, run it several times until no errors are found, then restart normally. Does this help at all?

    Another thing to check is the RAM. If you have the cd(s) or dvd that came with the computer, it should have either a separate cd called 'Apple Hardware Test' or it will be on the installer dvd. If you can restart with it in the tray, hold down the 'option' key immediately after the startup chime. You'll be presented with a blue screen with disk icons that show the available startup systems. Choose 'hardware test' and run the 'Extended Test'. This should tell if your RAM is not compatible with Panther or defective, and may also indicate any problems with the video card.

  9. #9
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    Thanks Boots, I'll try when I get home. (Im at work at the minute, but this is my only access to the net at the minute!!)

    Im furiously printing stuff out to try, so all is appreciated!!

  10. #10
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    Good call on the hardware CD Boots.

    ali: The fact that you saw screen issues in when booted to open firmware makes me think it is hardware problem. Sure rules out the OS, so no use testing or fixing that.

    Whether or not the hardware test CD shows works or shows you anything, I would be heading to an Apple repair center pretty soon.

    The good news is, if it is a logic board/video/screen issue, your data is probably fine.

    The bad news is, except for adding memory to the second slot, there is nothing you can do without voiding your warranty. If it was out of warranty - and you were very adventurous - you could crack it open. But other than swapping the hard drive and the memory in the first slot, there ain't much that can be done by a user.

    Good luck.
    "Imagine if every Thursday your shoes exploded if you tied them the usual way. This happens to us all the time with computers, and nobody thinks of complaining." -- Jef Raskin

  11. #11
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    damn, still struggling. I cant get it to boot from the Panther CD, so I rang the Authorized Dealer I bought it from and they suggested I remove the baseplate, and look for a small button near the battery, which I can't see.I asked if this would void my warranty, and he said No.

    Im wondering if he means the 2nd plate, i.e. the one with the Apple 'star shape screws'.

    Im at a friends house at the minute, and really really struggling!!

  12. #12
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    Not sure.

    Sounds like he is asking you to reset the PMU, which is a very small button on most machines.

    As for the base plate, there is the main one, covers the entire bottom, has an Apple logo in the center, and is attached with Torx screws (star shaped) You can remove this to get to the airport slot and the number two memory slot, so yes you can remove without any warranty issues.

    Check this and this for some insight as to what he is asking and how to do it.
    "Imagine if every Thursday your shoes exploded if you tied them the usual way. This happens to us all the time with computers, and nobody thinks of complaining." -- Jef Raskin

  13. #13
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    I found the PMU button, it is under the first plate, so i didnt need the star shape spanner etc, but alas it still didnt help.

    I think that it is a 'back to the shop' situation, and as its still under warranty, its more of an annoyance than a mjor problem.

    Damn, typical of my luck, ive been working with macs for 15 years, and as soon as i get my own decent one, it acts up!!

    Thanks for the help anyway!!

    I'll let u know what it was.....................

  14. #14
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    Default Power Supply?

    It sounds to me that the iMac's power supply is the likely suspect. Since the computer is only 5 months old, I'd recommend that you allow Apple a shot at fixing it. After all, you paid for that warrantee service...
    Tony

  15. #15
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    UPDATE!!

    Well, I managed to get it to boot from the Hardware Test/iMac Install CD, and selected Hardware Test from the bootup screen.

    Everything passed, apart from Video RAM, which said 'error found' or 'error occured' (working from memory here!!)

    So, the short version is, its going back.


    PROBLEM 2......................

    I have a folder on my HD which contains personal mpegs of my partner and I, and the apple centre the mac is going to has one of my partners ex-colleagues working there, so I would like to delete it before sending it.

    I can boot up in open firmware mode, so is there any command that I can do there to delete a specific folder??


    Thanks for the help so far guys!!

  16. #16
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    Default Calling Jazzbo

    I have a folder on my HD which contains personal mpegs of my partner and I, and the apple centre the mac is going to has one of my partners ex-colleagues working there, so I would like to delete it before sending it.

    I can boot up in open firmware mode, so is there any command that I can do there to delete a specific folder??
    Youse kinda in a pickle...no backups of pics? And no way to burn pics to cd prior to deleting.

    If you can boot into Single User Mode (command + S after startup chime), then I believe you'd have access to those specific files. We need the big Unix guns here for this one....
    In fact, there ought to be a way you could make an encryted (password-protected) disk image of those files, then delete the originals- prior to sending off the rig for repair. Sorry I can't help you on the specific commands though. First step really is to see if you can get to SUM.

  17. #17
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    Default UNIX commands help!!

    Hi all!!

    OK, so I have a problem with my iMac (see separate thread, link pasted below).

    I can boot into Single User mode, but have no idea what to do next.

    I want to delete a specific folder containing personal items before it goes back to the shop.

    Can anyone tell me how to do it using Single User mode commands??


    Thanks for all help received so far!!



    http://www.macgurus.com/forums/showthread.php?p=65938

  18. #18
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    www.osxfaq.com
    Learning Center:
    http://www.osxfaq.com/Tutorials/LearningCenter/
    Tips - http://www.osxfaq.com/Tips/

    ----------------------------
    To compress (zip) a file, use:

    <tt>gzip filename</tt> This will replace the file with a compressed version with the extension '.gz'

    To unzip:

    <tt>gunzip filename
    ------------------------

    removing a directory

    playing with directories

    </tt>You really think someone is going to take time at work to look at your files and stuff? they'll be busy enough doing what they are paid to do - fix it and get it working if possible.

  19. #19
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    Quote Originally Posted by TZ
    Open Firmware or Single User Mode?

    If you can run fsck, then yes, there are commands to tar (compress) a folder.

    You really think someone is going to take time at work to look at your files and stuff? they'll be busy enough doing what they are paid to do - fix it and get it working if possible.

    If you can't boot from an emergency FW drive, know what? remove the disk drive when you send it in. They can fix it and work on it w/o your hdd.

    You can find a lot of tips -
    http://www.osxfaq.com/Tips/







    So I can remove my HD without voiding my warranty??

    There is nt much to see under the base plate, without going under the next baseplate (start screws), and im guessing its warranty-voiding time if i go into that.

  20. #20
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    Default Removing files in Single-User mode

    If you know where you've stored the MPEG, it's simple to remove it in Single-User mode. The only twisty part from here is explaining what you'll be seeing as you work to get it done. Not to worry...

    First off, in Single-User mode, you'll have to run the fsck (filesystem check) and mount commands you'll see displayed on-screen to get your disk mounted writable. (For safety's sake, Single-User mode comes up with the disk mounted read-only.)

    After that, we're going to be using the following commands:

    cd - change current directory; navigates around folders
    ls - list files in the current directory
    rm - remove file

    We need to know where you've stored the MPEG file. If, for example, it's in the Movies folder under your home directory, and your "short" username is "ali":
    cd ~ali/Movies
    We're navigating through ali's home directory (~ali) and then into the Movies subdirectory ("folder"), making it the "current directory". In Unix-land, directories are separated by slash characters (/).



    (We need to talk about filename completion, a simply wonderful facet of working in the shells, either in Single-User mode or in the Terminal app. Here we go.) (This is everyone! If you use Terminal, read this!!)


    If there are spaces or other special characters in the directory name(s) through which you need to navigate, you're going to have to use backslashes (\) to "escape" the special characters. The easiest way is to use "filename completion" in the shell (the program running your terminal session in Single-User mode) to get to the directory you want. That's done by typing the first character or two of a file or directory name and then pressing the "tab" key until the one you want is displayed in your command. (Sounds tougher than it is!) Like this, and I'll use |tab| for the tab key:
    cd ~ali/M|tab|
    displays the list of all files/directories under ali's home directory which start with a capital M. Hit |tab| again and the first of those files is loaded into your cd command. Not the right one yet? Hit |tab| again and the next M-file is loaded in. When the right folder is listed, press Return and off you've gone, changing directory into that folder.

    You can chain these down through more folders, simply by continuing the "path" as it's being constructed, using |tab| along the way. For example:
    cd ~ali/M|tab||tab||tab|
    displays Movies Music... The third |tab| picks "Music/". We add 'A' to the end, press |tab|, and cycle through the list of files and directories under Music that start with capital A...
    cd ~ali/Music/A|tab||tab||tab|
    gets us to:
    cd ~ali/Music/All\ Sorts\ of\ Banjo\ Tunes/
    At which point we hit Return, navigating into the "All Sorts of Banjo Tunes" folder inside ali's Music folder. See the backslashes "escaping" the space characters? Handy! Makes the whole thing from the ~ through the last / a single "token" instead of five separate bits.

    The root directory of all files and directories is the / directory. If you have the file stored in, say, the Downloads folder in the root directory of your disk, cd /Downloads will take you there, at which point you look for and then delete the mpeg file.

    Once we're in the right directory, run
    ls
    The "ls" (that's ell-ess) command lists files, and you should spot "my movie.mpeg" sitting in there. To remove it:
    rm my|tab||tab|
    and keep pressing the |tab| key until the right file is teed up for removal
    rm my\ movie.mpeg
    and then hit Return. Rerun
    ls
    to verify that the file is, indeed, gone.

    That's it!

    Jazzbo
    Last edited by Jazzbo; 05-26-2004 at 07:23 PM.

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