7 Replies Latest reply: Feb 12, 2010 9:53 AM by Dah•veed
Anic264b Level 1 (20 points)

My neighbor's computer is experiencing some problems: it does not start (the screen stays black, no startup chime, but the fans run, as does the hard disk. Also, neither the mouse or the keyboard seem to be powered (no light)).

I have tried usual commands (reset PRAM and reset the SMC). Also tried with no device connected. (well, if something so trivial than all these tips did the trick, I wouldn't had to ask here ).

So, without keyboard, I couldn't even try special modes (safe, target disk, start from CD, etc), should the Mac be able to start in some mode. I have then decided to open the iMac (well, the warranty is way out, so nothing is lost). I have never seen a so-hard-to-open Mac, by the way (something was likely blocked).

I'm thinking of 4 possible causes for the problem:
-the hard disk could be damaged. It was malfunctioning some days ago. I assume it could come to a point where the logical board of the disk is failing;
-the RAM is an obvious possible cause;
-the CPU is also obvious;
-another component on the main board/logic board.
-I have forgotten a 5th point?

Well, I tried with unplugging the hard disk, and it had no effect, so it's not the HDD. I'm puzzled for the remaining ones (not knowing the iMac enough is a cause).

First, about the RAM, it seems the RAM slot is empty, so the actual RAM is somehow built-in (I haven't seen something seeming like usual RAM bars), so, if I can't remove the RAM, how can I test whether it's damaged or not?

Then, the CPU. There are 2 of them. So I thought I may take one out (and then the other one) and see whether the Mac starts. Well, I can't figure out how to remove the CPU cooling piece (there are just 4 "buttons" that can be pressed but nothing happen). I prefer asking here first, not removing the entire main board without advices.

Lastly, if it's the main board, I know I won't be able to do much. I have read there are LEDs to possibly diagnose power issues, but I don't see them (no LED is showing light, it seems). I'd like to test my other assumptions before thinking the main board is the cause.

Else, is there something I could try I have forgotten?

P.S: sorry for my (possibly) bad english, and the troubles of explanation; it's not as easy when english isn't the native language. I just wanted to mention that I have already repaired computers, so don't hesitate to tell me complicated answers.

Thanks in advance for your help.

MacBook Pro, Mac OS X (10.4.11)
  • Carolyn Samit Level 10 (103,360 points)

    If you have haven't tried, startup in Safe Mode

    What is Safe Mode

    *At the first link is information on how to boot in Safe Mode without the use of a keyboard.*


    Message was edited by: Carolyn Samit
  • Anic264b Level 1 (20 points)
    Hello Carolyn,

    Thanks for your answer. Unfortunately, when I say "the keyboard does not work", I mean the computer does not start far enough to even powering the USB ports (so it's not like the keyboard was broken, but, instead, the Mac can't start beyond simply turning on).
  • Dah•veed Level 7 (33,655 points)
    If the RAM slots are empty, someone has removed the RAM. There is no RAM on the logicboard. No startup chime means no usable RAM was encountered during Power On Self Test.

    Exactly what model of iMac is this?

  • Anic264b Level 1 (20 points)
    David.Austin.Allen wrote:
    If the RAM slots are empty, someone has removed the RAM. There is no RAM on the logicboard.

    This page does say some RAM is built-in: http://support.apple.com/kb/HT2266
    It explains why the RAM slot (which there is just one) is empty as there is not further RAM installed.

    No startup chime means no usable RAM was encountered during Power On Self Test.

    It may also mean some other problems, if I recall correctly (for instance, a dead CPU will prevent the chime, because the chime indicates all has passed).

    I have the feeling that we aren't talking about the same model, because, according to:
    the LED should blink when there's no RAM. In my case, the LED stays on.

    Exactly what model of iMac is this?

    It's an iMac third generation 20'' isight (put the terms in the order you want ). EMC is 2082.

    Thank you for this answer. Does not solve my problem but is useful in progressing.
  • Dah•veed Level 7 (33,655 points)
    You are mixing up Apple Knowledge Base articles. The first one refers to an iMac G5, a PowerPC-based iMac with a CPU from IBM and Apple stopped manufacturing them in MAR 2006. The second article refers to Intel-based iMacs that Apple has manufactured since JAN 2006.

    The EMC 2082 is a 3rd generation iMac G5, which is an IBM PowerPC-based iMac, the 1st generation with an iSight. Yes it has 512 MB of RAM on the logicboard.

    You are posting in the Intel-based iMac Apple Discussion forums. Hence the mixup about whether it does or does not have built-in RAM.

    You should be posting to get the correct assistance in this forum;

  • Anic264b Level 1 (20 points)
    Thanks. It's true I was not sure which articles referred to what model. Thank you for your help, and sorry about posting in the wrong forum.
  • Dah•veed Level 7 (33,655 points)
    De nada.