Al, Yes, my mistake. It’s an Early (note “Late”) 2009 A1225 iMac. That makes no difference in my comments. Thanks for the “illegal” photo. Yep, that’s a video card issue.
As you’re not eager to go inside your iMac, I suggest you ask the local Mac shop how much they would charge to diagnose your iMac using Apple diagnostic software (Apple Service Diagnostics 3S132, both OS and EFI test modes) to confirm the video card issue. If the card is the issue, then the shop will have to remove the logic board in order to replace the card or have it repaired. That is the perfect time to clean out all the dust as well as check/replace the clock battery. If the iMac passes the tests, I still would have the iMac cleaned out inside. It also wouldn’t hurt to replace the clock battery (CR2032) as well as pull the RAM sticks, clean their contacts, then reinstall them. I’ve been inside lots of Macs, and I’m always amazed at how much dust is inside, especially units like yours that are infrequently restarted. IIRC, Mavericks is one of the recent versions of OS X that relaunches all apps that were running before a shutdown or going to sleep. As you note, the more windows you have open, the more noticeable the problem. You may have a memory leak that forces the iMac to struggle to relaunch all the windows correctly, but my money is on a dying video card that has one or more solder joints that open when warm but are closed when the machine is cold. If you’ve got another Mac and can connect them with a Firewire cable, Valter’s suggestion that you start your 24” iMac in Firewire Target Disk Mode and then start the other Mac and select the 24” iMac’s hard drive as the boot disk by holding down the Option key to launch the Picker is a good way to isolate the hardware/software issue. You will have to let the two machines run for a while, most likely. If the video issue occurs on the “new” Mac’s screen, then it’s software; if it doesn’t, then it’s the 24” iMac’s hardware. Good luck. Jim Scott > On Aug 5, 2016, at 6:55 AM, Al Poulin <alfred.pou...@gmail.com> wrote: > > Thank you Valter and Scott, > > To clarify a couple things. The iMac is an "Early 2009" Display Port, if that > makes any difference. I meant "multiple windows," actually up to maybe 9 or > 10, plus the 30 Desktop icons. > This never happens after shutting down and on a fresh start up. I shut down > maybe a couple times a month to clear cobwebs. > > I live in Northern Virginia. There is a Mac repair shop nearby in Maryland > that I could call. I'm not keen on the alternative of lifting the glass > screen off the case myself. > > Sample photo attached (I think). > > Al Poulin > > On Thursday, August 4, 2016 at 10:32:52 PM UTC-4, Jim Scott wrote: > > > On Aug 4, 2016, at 5:19 PM, Al Poulin <alfred...@gmail.com> wrote: > > > > Greetings, > > > > Am I looking at a hardware problem or misbehaving software? > > > > My workhorse is the last 24 inch iMac that Apple produced. Running 10.9.5 > > Mavericks. > > Early 2009 “Display Port” > > 2.66GHz Intel Core 2 Duo > > 4GB RAM > > 640GB HD > > SuperDrive > > NVIDIA GeForce 9400M graphics with 256MB of shared DDR3 memory > > > > When waking from sleep, occasionally the display will scramble for about 5 > > or 10 seconds before organizing itself. This seems to happen more when > > multiple screens are left open, even as few as three. Or, it may go black > > for a few seconds and then settle down. There are 30 to 35 items on the > > Desktop. > > > > This has been happening for two or three years, but seems to be more often > > now. > > > > If this is hardware, should I eventualIy expect total failure of the screen > > to display properly and prevent access to the system? > > > > Thanks, > > Al Poulin > > Al, > > iMacs of that vintage and screen size tend to develop issues with the video > card, which is plugged into a slot on the logic board and has a finned heat > sink with lots of piping. The card and heat sink sit at the bottom of the > logic board and are directly above the air intake vents at the bottom of the > case. Since the video chip itself is attached to the card with hundreds of > little solder dots (the notorious BGA or ball grid array), any overheating of > the card or chip can cause one of more of those solder joints to weaken > and/or crack. Thus any accumulation of dust or dust bunnies that blocks the > cooling fins can be bad news for the BGA and thus video performance. The > finned heat sink for the cpu is directly above the video card heat sink, so > there’s an impact on the cpu also if there’s blockage. > > I have seen exactly the pixelization you describe as scrambling in video > cards that ultimately fail after many heat up/cool down cycles. The problem > is accelerated dramatically by dust buildup blockages of the cooling fins. > > So, yes, I believe you are experiencing the symptoms of a failing video card. > You can open the case, disassemble things enough to clean out the dust. But > the damage won’t be reversed, although failure may be delayed by the > cleaning. The good news is that the card can be replaced. The bad news is > that new cards are hard to find and pricey. Used cards also can be hard to > find and equally pricey, and there’s no guarantee that they won’t soon fail > too. > > I have used a couple of repair services advertised on eBay, with mixed > results. Reflowing the solder joints is a standard approach, and often > restores a card to working order. However, internal arcing causes damage and > a reflowed chip quite often fails again, for good. Thus I no longer ask for a > reflow. Rather, I pay a few more dollars (@ $150 or so) and get a brand new > video chip installed. New chips come complete with the BGA solder balls, > which makes removal or the old chip and installation of a new one a breeze > for someone with a high end work station and the training and experience. > > However, it’s getting more and more difficult to find a repair service that > has the proper replacement chips. So you’ll have to do a lot of digging to > find a vendor who not only has the correct video chip for your Late 2009 > A1225 24” iMac, but also is willing to do the repair on a card that’s already > exhibiting symptoms. Go into About This Mac and determine exactly which of > the three video cards available in your model has been installed. Then go > looking for a vendor who has that chip in stock and will install it. I have > found eBay vendor/seller brickfence (he’s in the L.A. area) to be highly > reliable, honest and easy to deal with during multiple transactions over > several years. But there are lots of others, so do careful shopping and check > their feedback. > > Jim Scott > Eureka, CA > > -- > You received this message because you are a member of the iMac Group, a group > for those using Apple iMacs and eMacs. > The list FAQ is at http://lowendmac.com/imac/list.shtml and our netiquette > guide is at http://www.lowendmac.com/lists/netiquette.shtml > To post to this group, send email to imaclist@googlegroups.com > To leave this group, send email to imaclist+unsubscr...@googlegroups.com > For more options, visit this group at http://groups.google.com/group/imaclist > > --- > You received this message because you are subscribed to the Google Groups > "iMac Group" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to imaclist+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > <IMG_1553.JPG> -- You received this message because you are a member of the iMac Group, a group for those using Apple iMacs and eMacs. 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