12 Replies Latest reply: Sep 28, 2012 9:30 AM by johng1950
JJGraphics Level 1 Level 1 (30 points)

My neighbour's iMac starts and runs normally most of the time, but periodically when running emits three beeps and then freezes. This is NOT the usual "three beeps at startup" indicating a RAM problem, but whilst the machine is is actually being used.

 

Can't seem to find anything about this anywhere. Any ideas, anyone?

 

(The logic board was replaced very soon after purchase as the machine had all sorts of problems . . .)

  • justin119 Level 1 Level 1 (0 points)

    I've never heard of this happening at anytime other than system startup and as you suspected is usually caused by faulty RAM.


    What model Mac, ram amount, etc,. and troubleshooting have you tried so far?

  • Rod21 Level 1 Level 1 (45 points)

    I have seen this before on a few macs and it has come down to the Ram 95% of the time, it can be possible for the machine to POST but hang on a certain part of the memory when being used.

     

    Since you have had the logic board replaced i would double check the ram.

    Is it still the apple orginal ram in the imac?

  • JJGraphics Level 1 Level 1 (30 points)

    Its a fairly new Intel iMac (about 10 months old). 4Gb RAM

     

    So far I have re-seated the RAM, run with only one DIMM in place alternating the use of both modules.

     

    Been a Mac user and support specialist since MacSE days . . . never seem anything like this before.

  • JJGraphics Level 1 Level 1 (30 points)

    Rod21,

     

    Yes, its still just the original RAM as supplied.

  • Rod21 Level 1 Level 1 (45 points)

    Yes it is an odd error, and generally the system should only beep 3 times when rams not detected.

     

    If you have access to 2 new ram chips, try replacing both at same time.

  • JJGraphics Level 1 Level 1 (30 points)

    Thanks all for the suggestions. I'll borrow some DIMMs and try exchanging them. It may be a while before I am able to report back.

  • Joe Pyrdek Level 1 Level 1 (140 points)

    Had a MBP do this for a user a month or two ago.  It passed POST and ran fine for a couple of hours then 3 Beep and had to do a Panic forced shut down.  Same thing happened the next day after an hour or two.  Substituted a memory stick from another machine (only used one to force the machine to reset its internals) then did it with a second stick added.  Ran fine for a day or so of testing.  Put old sticks in, and it was back to about a three hour failure/freeze.  Purchased new (higher capacity) sticks and no problems reported after several weeks of use by the owner.

     

    I forget exactly what gerts reset when you run with a changed RAM amount and I can not find the article that explained this but I remember that doing this was the reccomended way to reset something.  Take a good look through the KB and you may find the article or someone else here might know where to find it.

  • JJGraphics Level 1 Level 1 (30 points)

    Sorry this took a long time, but the issue was definitely bad DIMMs.

     

    I swapped out the original DIMMs for a new set and the problem went away.

     

    Then followed a process of swapping the original DIMMs around to establish which was bad. The bad ones (there were actually two) were returned to Kingston who replaced them under the "Lifetime Warranty."

     

    As a side issue, when the faulty DIMMs were in place, the machine would occasionally emit a sharp crackling sound like an electrical short-circuit through the loudspeakers. This problem was also resolved when the new DIMMs were installed.

  • queue517 Level 1 Level 1 (0 points)

    Thanks so much for this thread, as I am having the EXACT same problems (including that weird electrical crackling).  Can you tell me how you went about returning the bad DIMMs?

  • JJGraphics Level 1 Level 1 (30 points)

    The bad DIMMs were returned to the dealer who originally supplied them and were very quickly replaced by Kingston. Dealer then sent me the replacements.

  • Anic264b Level 1 Level 1 (20 points)

    JJGraphics wrote:

     

    As a side issue, when the faulty DIMMs were in place, the machine would occasionally emit a sharp crackling sound like an electrical short-circuit through the loudspeakers. This problem was also resolved when the new DIMMs were installed.

    How would someone explain this sound? Is it a hardware issue or a software one (I imagine it can be either one)?

  • johng1950 Level 1 Level 1 (0 points)

    My imac mid 2010 worked fine with "new" memory for 6 months, then started hanging in mid-session - meaning it froze and beeped loudly hours or days after it booted OK. Put old memory back in and noticed it ran more smoothly with less memory than more. Put the "new" memory back in and ran memtest for days and days; no problems reported. But, the system still froze after I'd been working for a while - at odd times. So, took the "new" memory back to the store, and, while there, upgraded to (more expensive) Crucial brand memory - just to be on the "safer" side. Put the replacement memory in and my imac has never run better - not even when new. So far, my imac is quieter, cooler, and smoother now than since the day I bought it. Thought I'd post this on this old thread because Apple Care had told me to bring the machine to them for three days of testing - per other posts I'd seen on the net. But, that would have been a complete waste of time - since they'd wind up (with the old memory) telling me "no problem," or, (with the "new" memory,) "it's a non-apple part problem." Meanwhile, bad memory can mean bad writes to your hard drive; mine seems fine, but I generally pay close attention to problems and fix them asap, or, sooner. If you wait until you have additional problems, you may spend a lot more time and money getting things finally done - and you may wind up back at "square one" or worse if you trash your drive and it's contents.